Issued May 28, 1908. U. S. DEPARTMENT OF AGRICULTURE, BUREAU OF ANIMAL INDUSTRY. BULLETIN 106. A. D. MELVIN, CHIEF OF BUREAU. I WERIMENTS ON THE DIGESTIBILITY OF PRICKLY PEAR BY CATTLE. BY R. F. HARE, Professor of Chemistry in the College of Agriculture and Mechanic Arts of the Territory of New Meidro. f California Regional facility WASHINGTON: GOVERNMENT PRINTING OFFICE. 1908. Issued May 28, 1908. U. S. DEPARTMENT OF AGRICULTURE, BUREAU OF ANIMAL INDUSTRY. BULLETIN 106. A. D. MELVIN, CHIEF OF BUREAU. EXPERIMENTS ON THE DIGESTIBILITY OF PRICKLY PEAR BY CATTLE. . : BY R. F. HARE, Professor of Chemistry in the College of Agriculture and Mechanic Arts of the Territory of New Mexico. WASHINGTON: GOVERNMENT PRINTING OFFICE. 1908. LETTER OF TRANSMITTAL. U. S. DEPARTMENT OF AGRICULTURE, BUREAU OF ANIMAL INDUSTRY, Washington, D. C., March 13, 1908. SIR: I have the honor to transmit herewith and to recommend for publication as Bulletin 106 of this Bureau a manuscript entitled "Experiments on the Digestibility of Prickly Pear by Cattle," by R. F. Hare, Professor of Chemistry in the College of Agriculture and Mechanic Arts of the Territory of New Mexico. While the experiments reported in this paper were conducted by Professor Hare in cooperation with the Bureau of Plant Industry, it has been thought advisable to publish the paper as a bulletin of the Bureau of Animal Industry, inasmuch as it deals primarily with the animal side of the subject. Very respectfully, A. D. MELVIN, Chief of Bureau. Hon. JAMES WILSON, Secretary of Agriculture. 3 LETTER OF SUBMITTAL. U. S. DEPARTMENT OF AGRICULTURE, BUREAU OF PLANT INDUSTRY, Washington, D. C., February 10, 1908. SIR: I have the honor to transmit herewith and to recommend for publication as a bulletin of the Bureau of Animal Industry the accom- panying manuscript entitled "Experiments on the Digestibility of Prickly Pear by Cattle." This paper was prepared by Prof. R. F. Hare, chemist, College of Agriculture and Mechanic Arts of the Territory of New Mexico, under cooperative arrangements with this Bureau, and was submitted for the purpose of publication by Prof. W. J. Spillman, in charge of Farm Management Investigations. In previous bulletins of the Bureau of Plant Industry and the Agri- cultural Experiment Station of New Mexico much information has been published upon the practical use and the chemical composition of a large number of prickly pears and other cacti. The value of a feed, however, is not determined by the chemical composition alone; it is also necessary to know the percentage of digestibility of the nutri- ents found by the chemist. This information is supplied in the accompanying manuscript . Respectfully, B. T. GALLOWAY, Chief of Bureau. Dr. A. D. MELVIX, Chief, Bureau of Animal Industry. CONTENTS. Page Introduction 7 Method of conducting digestion experiments 7 Definition of some technical terms and discussion of the functions of foods 8 Composition of feeding stuffs 9 Function of the nutrients 11 Method of determining the digestible nutrients of prickly pear from the com- position and digestion coefficient 11 Preparation of standard rations 12 Plan of the experiments 14 The animals used 14 The different rations used 15 Description of the stalls 15 The feeding 1 <> Collecting the feces 17 Collecting the urine 17 Preparation of the samples 18 Report of the experiments 18 Experiment No. 1. Digestibility of prickly pear (Opnnlia lindheimeri). . . 18 Experiment No. 2. Digestibility of prickly pear (Opuntia laris?) 21 Experiment No. 3. Digestibility of prickly pear (Opuntia engelmannii cycloides ) and alfalfa 23 Experiment No. 4. Digestibility of prickly pear (Opnntia engelmannii cyclmdfs ) and cotton-seed meal 25 Experiment No. 5. Digestibility of a fair quality of second-cut alfalfa. .... 29 Effect of prickly pear on the digestibility of other feeding stuffs 31 Income and outgo of nitrogen 35 Conclusions... 37 ILLUSTRATIONS. PLATK. Pfge. PLATK I. Fig. 1. Opuntia lindheimeri. Two-year-old second growth of species fed in the first exj)eriment. Fig. 2. Opuntia engelmannii cy- cloidfs. Old plants of .species fed in the third experiment 8 TEXT FIOl'KK. FIG. 1 . The stalls used in experiments Nos. 2 to 5 16 EXPERIMENTS ON THE DIGESTIBILITY OF PRICKLY PEAR BY CATTLE. INTRODUCTION. Many chemical analyses have been made of a number of different members of the cactus family to determine their value m a feeding stuff for animals." With this data we are enabled to judge with a fair degree of accuracy the amount of the various r.utrients con- tained by many different species of this group of plants, as well as by different parts of the same plant. However, as no record of diges- tion experiments with any of the cacti has bsen found, it was impos- sible to say what proportion of the different nutrients were available to the animals. The increased use of the prickly pear (the flat- jointed members of the genus Opuntia) as a feed for all classes of ruminants, especially for range and dairy cattle, makes it important for the proper preparation of a ration that the feeder know how much digestible nutrients to expect from feeding a given quantity of the plant either alone or mixed with other feeding stuffs. The following experiments have therefore been conducted to determine the digesti- bility of prickly pear and thus guide the feeder in the preparation of rations from this plant. The investigations have been conducted in cooperation with the Office of Farm Management Investigations, Bureau of Plant Industry, United States Department of Agriculture. The author acknowl- edges the assistance of Dr. David Griffiths, of that Office, who has spared neither time nor pains in an effort to make the experiments successful. Acknowledgment is made of the careful and painstaking analytical chemical work of Messrs. S. R. Mitchell and II. B. Deemer. METHOD OF CONDUCTING DIGESTION EXPERIMENTS. The principle of conducting a digestion experiment is very simple. First, the animal is fed on the feeding stuff the digestibility of which is to be determined until all other feeds have been removed from the alimentary canal, when the animal is said to be in a condition of equi- librium with this feed. The animal is then placed in a stall specially designed for feeding and for collecting refuse and excreta without waste. It is then fed a weighed amount of the feeding stuff, the com- position of which is determined by analysis. All the refuse is col- lected, weighed, analyzed, and the amount of the several nutrients See Bulletin 60 of the New Mexico Experiment Station. 8 DIGESTIBILITY OK PRICKLY PEAR BY CATTLE. which it is found to contain is subtracted from the amount of the corresponding nutrients fed. As nearly as possible that portion of the feces which corresponds to the weighed feed eaten is carefully collected, weighed, and analyzed. The amount of the different nutrients found in the feces subtracted from the amount eaten gives the amount of each nutrient digested. This result, multiplied by 100 and divided by the amount eaten, gives the percentage of digestible nutrients, which is called the "coefficient of digestibility." DEFINITION OF SOME TECHNICAL, TERMS AND DISCUSSION OF THE FUNCTIONS OF FOODS. Most of the readers of these pages will doubtless be familiar with the technical terms that are used throughout this bulletin and under- stand how the value of a feeding stuff is determined from its analysis and from the digestion coefficient of the several nutrients, but it may not be amiss briefly to define and discuss them here for the benefit of the few who may not be thoroughly familiar with them. For this reason there are given below definitions of some of the terms used, with the names of the constituents that are usually determined in fixing the value of a feeding stuff, and a brief discussion of the func- tions of each in the animal body. It should be remembered that in the feeding of animals the amount of nourishment obtained from any feed by an animal does not alto- gether depend upon the weight of the feed taken into the body. Green matter, for instance, with 60 to 05 per cent of water w r ill not, of course, furnish as much substance as will cured fodders and grains. The scientific feeder must not only prepare the rations for his animals on the basis of the amount of dry matter present, but it is also neces- sary that he should know how much nourishment a given amount of this dry matter can furnish them. The dry matter of the different feeds has been found to vary greatly in the amount of nutrients which it contains as well as in its digestibility. A feed which has been adulterated with cotton-seed hulls, chaff, sawdust, or other fibrous and insoluble or difficultly soluble matter would not, for instance, be as digestible, and consequently could not furnish as much nourish- ment pound for pound, as some feed in which the nutrients were in a form more readily available to the animal. It is, therefore, not only necessary that the amount of dry matter in a feed be known, but it is equally important to know the character and composition of this dry matter. The animal body is made up of water, mineral matter (or ash), nitrogenous matter (or proteids), and fat. The function of the feed which animals eat is to maintain the supply of this material so that they may grow, perform work, and maintain a healthy condition. BUL. 106, BUREAU OF ANIMAL INDUSTRY, U. S. DEPT. OF AGRICULTURE. PLATE I. FIG. 1. OPUNTIA LINDHEIMERI. TWO-YEAR-OLD SECOND GROWTH OF SPECIES FED IN THE FIRST EXPERIMENT. FIG. 2. OPUNTIA ENGELMANNII CYCLOIDES. OLD PLANTS OF SPECIES FED IN THE THIRD EXPERIMENT. DEFINITION OF TECHNICAL TERMS. 9 It is a well-established fact that all feeds have certain groups of substances that perform their peculiar functions in building the dif- ferent parts of the animal body, and the object of a chemical analysis of any feeding stuff is to separate and determine these groups. They are usually separated into the following: Water, ash, ether extract, crude fiber, protein, nitrogen-free extract, and organic matter. The last named represents a sum of the preceding four, and together with the mineral matter they are all called nutrients. The value and function of each of these classes of nutrients are briefly discussed below. COMPOSITION OF FEEDING STUFFS. Water. All foods, however dry they may appear, contain some moisture. Air-dry corn meal or wheat flour, for example, which may appear perfectly dry will, on the complete removal of their water, be found to have contained from 5 to 15 per cent. Some root crops and vegetables may contain as much as 95 per cent, or even more, of water. The water naturally present in feeding stuffs may cause them to be more succulent and thus doubtless aids their diges- tion, but an increase in the water means a necessary decrease in the actual amount of food material present, hence its presence instead of adding to merely detracts that much from the value of any feed; especially is this true of the concentrated feeds. Mineral matter, or ash, is that portion which is left after complete combustion of the plant. While a certain amount of ash is necessary for supplying mineral matter to animals and in building bones in the young, there is usually an abundance present in all foods; and for this reason no commercial value is placed on the amount of ash con- tained in the food, as is the case with proteids, carbohydrates, and fats. Protein is a name given to a group of very complex compounds which are characterized by the fact that they all contain the element nitrogen combined with carbon, hydrogen, oxygen, and small amounts of sulphur and sometimes phosphorus. Albumen of eggs, casein of milk, and fibrin of blood are examples of protein compounds. Pro- tein is that material in the food which serves as a flesh former, and is the only substance of the food that can be used to build muscular tissue, skin, hair, horns, blood, and connective tissue. It may also, when in abundance, serve the function of the carbohydrates and fats of the food. Alfalfa, cotton-seed meal, all the clovers, and wheat bran are examples of feeds rich in this nutrient; while prickly pear, straw, roots, and tubers contain it in very small amounts. Because of its importance in the dietary, and the fact that it is not present in sufficient amounts in all feeds to supply the needs of animals, it is usually the most expensive of all the nutrients. In one State having 34749 -Bull. 106-4)8 10 DIGESTIBILITY <>F PRICKLY PEAR BY CATTIE. a feeding-stuff law a value of 2.3 cents a pound was placed upon the protein which the food contained, while the carbohydrates (nitrogen- free extract and crude liber) and fats were priced at 0.94 and 1.14 cents, respectively. This is about an average of the prices usually placed on these nutrients. In the Southwest, where alfalfa, wheat bran, anil cotton-seed meal are three of the principal feeds, animals usually get an excess of protein over the amount which they require, and this excess is undoubtedly used to serve the function of the fats and carbohy- dratesthat is, to furnish heat and other forms of energy and to produce fat. Because of the fact that the feeds mentioned above are the most abundant ones for this section, if a commercial value were placed on their various nutrients the proteids should be cheaper than the carbohydrates and fats, and such is often the case. Wheat bran, cotton-seed meal, and alfalfa are usually found to be cheaper than corn and other starchy grains and hays. While the various groups of proteid compounds are alike in that the element nitrogen is common to them all, they vary greatly in the proportional amount of nitrogen which they contain as well as in their value for building flesh and muscle. Strange to say, it is not those groups which contain the most nitrogen that are the most valuable for this purpose. Those of most value as flesh formers are the so-called true proteids, or albumin-like substances that contain about 16 per cent of nitrogen. These are most abundant in grains and mature fodders. There are simpler groups of protein compounds which the chemist calls amids and amins, or better, nonproteid nitrogen compounds. They may contain 20 per cent or more of nitrogen. They are the first products formed by the plant in the synthesis of nitrogen compounds from the ammonia of the soil. They may be found in the young and tender parts of the plant or in the fruits, and in roots and tubers. It has been shown that these nonproteids can prevent the waste of tissue when used as a sub- stitute for albumin in food, but they are unable to replace the latter in building flesh. Fat is the portion that is dissolved when the dried powdered food is treated with ether. This treatment theoretically dissolves fats only, but practically small amounts of gums, resins, chlorophyll, and other substances go into solution with this reagent, and the material thus dissolved is often and perhaps better termed ether extract. The fats, like the carbohydrates, are used as heat and energy producers, and they are about two and one-fourth times as valuable as the latter for that purpose. One pound of fat yields 4,220 calories." "One calorie is the amount of heat required to raise the temperature of 1 kilogram of water 1 degree Centigrade, or 1 pound of water 4 degrees Fahrenheit. DETERMINING THE DIGESTIBLE NUTRIENTS. 11 Crude fiber is the portion of the food that constitutes the frame- work of the plant. In the analysis it is the part remaining after the finely ground food has been thoroughly treated successively with ether and hot dilute acid and alkali. Nitrogen-free extract is represented by the sugars and starches, and includes all of those compounds of carbon, hydrogen, and oxygen that are dissolved by boiling the fat-free material consecutively for thirty minutes each in dilute acid and alkali of definite strengths. All of this group of bodies, together with that part of the crude fiber which is digested by the animal, are collectively called carbohydrates. They serve the same function as the fats in the animal system, but are not so concentrated a food. One pound of carbohydrates yields about 1,860 calories, hence we say that fats which yield 4,220 calories per pound have two and one-fourth times the value of carbohydrates as heat producers. FUNCTION OF THE NUTRIENTS. The two main functions of food are to produce tissue and to fur- nish energy. Proteids alone are used for the former purpose, while fats, carbohydrates, and excess of proteids can all be used for the latter. The amount of food used for building tissue is comparatively small, hence the ratio of proteid to nonproteid nutrients may be quite wide, especially for grown animals that are doing hard work. Since the important functions of any food are performed by the proteids and nitrogen-free nutrients (fats and carbohydrates) they contain, the amount of these present and in a form available to the animal is a measure of the value of that food. METHOD OF DETERMINING THE DIGESTIBLE NUTRIENTS OF PRICKLY PEAR FROM THE COMPOSITION AND DIGESTION COEFFICIENT. An average of several analyses of a certain variety of prickly pear (Opuntia lindheimeri) shows it to have the following composi- tion: Water, 83.41 per cent; ash, 3.48 per cent; protein, 0.75 per cent; ether extract, 0.31 per cent ; crude fiber, 2. 64 per cent ; nitrogen- free extract, 9.41 per cent; total organic matter, 13.11 per cent. By feeding this plant to steers we find the following coefficient of digestion of the nutrients present for this class of animals: Pro- tein, 58.25 per cent; fat (ether extract), 67.90 per cent; crude fiber, 41.32 per cent; nitrogen-free extract, 82.59 per cent. With these figures we calculate the following digestible nutrients from the above analyses by multiplying each nutrient by its coefficient: Proteids, 0.45; fat, 0.21; carbohydrates, 7.77. The nutritive ratio, or the ratio between digestible proteids and nitrogen-free material, i. e./ fat X 2.25 + total carbohydrates, in this sample of the plant, is 1 to 18.3. 12 DIGESTIBILITY OF PRICKLY PEAR BY CATTLE. PREPARATION OF STANDARD RATIONS. As before stated, the value of a feed does not necessarily depend upon the amount of proteids, carbohydrates, and fats which it con- tains, but rather upon the amount of these contained in the feed that is available to animals. If digestion experiments show that a comparatively large amount of the nutrients pass into the feces, then in order that the animal may secure sufficient nutrients to supply the purpose sought there must be a corresponding increase of the ration. For the guidance of the feeder in the proper prepa- ration of his ration, the digestion coefficient has been determined for practically all ordinary feeds and for the several kinds of farm animals. Experience has proven that the best results are obtained in feeding when the digestible nutrients are fed to the animal in certain definite amounts. Tables of feeding standards have been compiled by German and American scientists in which are given the daily amounts of each nutrient required by our common farm animals of a given weight and for a specific purpose. In the feeding of milch cows, for example, the standard fixed by the German scientist Wolff is the one probably most used in this country at present. It is based on observation of the feeding practices of the best German feeders, together with feeding experiments by trained specialists. There is a prevalent opinion in the United States that the Wolff standard for milch cows is somewhat higher in proteids than is necessary for the best American ration. Several attempts have been made by scientists in the United States to determine what the proper standard is for this country. Below is given a table taken from the Connecticut (Storrs) Experiment Station report for 1894, in which is given the German standard, together with four rations which have been proposed by different authorities for the United States. TABLE 1. Herman (Wolff's) standard ration, together with averages of some American rations and a tentatively suggested ration per 1,000 pounds lire weight. Ration* Organic matter. Digestible nutrients. Nutri- tive ratio. 1:5.4 1:6.9 1:6.5 1:6.3 1:5.6 Protein. *-,, t Carbo- at - hydrates. Fuel value. rounds. Wolff's (German) standard. . .. '-4.0 round*. 2.50 2.15 2.48 2.51 2.50 rounds. 0.40 .74 .94 .90 .5 to .8 Pounds. 12.50 13.27 14.09 13.92 13 to 12 Calorif.i. 29,600 31,250 34,800 34,350 31,000 Average of 128 American rations, com- piled by the Wisconsin Experiment Station . . 24.5 Average of 1(1 rations as fed in Connecti- cut in 1892-93 26.4 Average of 25 rations as fed in Connecti- cut in 1892-94 26.8 Tentatively suggested ration 25 In this suggested ration the fuel value could 1* supplied by about 0.5 pound of digestible fat and 13 pounds of digestible carbohydrates; by 0.6 pound of digestible fat and 12.5 pounds of digestible carbo- hydrates; or oy 0.8 pound of digestible fat and 12 pounds of digestible carbohydrates. PREPARATION OF STANDARD RATIONS. 13 It will be seen from the table that about the only material change recommended by American scientists consists in an increase of the fats and carbohydrates. It would appear that this much difference might almost result from individuality, and the feeder would be safe in using any of these rations that common sense, good judgment, and his experience with the individual animals would indicate to him to be best. In New Mexico, where proteid feeds are cheap, the nutri- tive ratio of the Wolff standard would probably not be too narrow. In fact, narrower rations than those proposed by him are used here constantly with splendid results. By the use of the above table a balanced ration can be prepared from prickly pear when its digestible nutrients are known, by so mixing it with other feeds as to obtain the nutrients in the right pro- portion. Suppose, for example, we desire to prepare a ration com- posed in part of prickly pear for a 1,000-pound milch cow yielding 22 pounds of milk per day. Using the Wolff standard of 2.5 pounds protein, 0.5 pound fats, and 13 pounds carbohydrates as our basis, and feeding 100 pounds of prickly pear per day, the cow would get the following nutrients, as calculated above from the species Opuntia lindheimeri: Proteids, 0.45 pound; fats, 0.21 pound; carbohydrates, 7.77 pounds. This leaves a balance of 2.05 pounds protein, 0.29 pound fat, and 5.23 pounds carbohydrates to be supplied by some other feed. Since the ratio of proteids to nonproteids (nutritive ratio) in this variety of pear is 1 to 21. 7) and a ratio of 1 to 5.7 is the Wolff standard for such a cow, it is evident that some feed rich in protein should be mixed with the prickly pear to narrow it down to this ratio. Cotton-seed meal, wheat bran, or alfalfa could be used for this purpose, but cotton-seed meal, if fed in quantity, contains so much protein that it makes, perhaps, too narrow a ration for the best results; besides, animals scour when fed cotton-seed meal and prickly pear alone, and if possible these should be fed in connection with some cured fodder. In Bulletin 60 of the New Mexico Experiment Station a balanced ration of prickly pear is discussed and rations containing this feed are suggested. At the time the bulletin was written the coefficient of digestion for prickly pear had not been determined, and in calcu- lating the rations its digestibility was assumed to be the same as that of green corn fodder." That the digestion coeflicient of prickly pear, calculated from the coefficient of green corn fodder, is very similar to that obtained from actual digestion experiments may be seen from the table following. " Sr HullHin 77, Office <>f KxjH'ritncnt Stations. I'niu-d Stairs Depart incut of Agrirultuiv. p. 82. 14 DIGESTIBILITY OF PRICKLY PEAR BY CATTLE. TABLE. 2.--Total nutrients of prickly pear (Opnntia lindheimeri). tht digestible nutri- ents as obtained by experiment, anil the calculated digestible mttru-nts obtained by using the digestion coefficient of green corn fodder. Name of nutrient. Protein. Fat. Nitrogen- free Filter, extract. Carbo- hydrates. Prirkly pear: Composition Digestible nutrients as determined Digestible nutrients as calculated from- data obtained with green corn fodder. Per cent. Per cent. Per crnt. ' Per cent. Per cent. 0.75 0.31 9.41 2.61 2.01 .44 .21 1.09 .49 1.7t> R.C3 from the foregoing table it may be seen that the coefficients of digestion of green corn fodder that were used for calculating the digestibility of prickly pear in the preparation of a balanced ration in Bulletin 60 are sufficiently close to allow the ration there given to remain unchanged. The proteids of the prickly pear do not appear to be quite as digestible as those of green corn fodder, the fats are about the same in both, while the nitrogen-free extract is more for the prickly pear, the crude fiber is less, but the total digestible nutrients are about the same, being slightly in favor of prickly pear. PLAN OF THE EXPERIMENTS. THE ANIMALS USED. Five different digestion experiments are included in this study. In all cases wild range steers from 2 to 3 years old were the animals selected. The steers being very wild were quite difficult to handle properly, but it seemed impossible to get tame steers and at the same time those accustomed to eating prickly pear. In fact, a gentle steer is practically unknown on the ranges. Plenty of milch cows were available, but were not used because of the difficulty of keeping separate the liquid and solid excreta. Both sheep and goats eat prickly pear, but none that could be used in this work were found convenient; besides, steers were preferred, it being deemed more desirable to get the data for cattle, since they are fed this plant more extensively than are any other animals. Experience has shown that there may be a slight difference between the digestion coeffi- cient obtained from sheep, goats, and cattle, yet for all practical purposes this factor may be assumed to be the same for all ruminants. Two steers were used in each of the experiments so as to minimize any difference due to individual animals or slight errors due to manipulation. It is usually customary to use two animals in this work; sometimes more are used, and of course the larger the number the more trust wort hv should be the result. PLAN OF THE EXPERIMENTS. 15 THE DIFFERENT RATIONS VSED. The first experiment was conducted at San Antonio, Tex., in January, 1906. In this experiment the steers were fed prickly pear alone for about three weeks. During the last four days they were confined in stalls and all their feed and refuse were carefully weighed, the feces and urine being collected in a manner described later. Experiments Nos. 2, 3, 4, and 5 were all conducted in the spring of 1907 at the Agricultural College of New Mexico. Grade Hereford steers were used in each experiment. In experiment No. 2 prickly pear was fed alone, as in experiment No. 1 conducted at San Antonio the previous year. In experiments Nos. 3 and 4 prickly pear was mixed with other feeding stuffs (alfalfa in experiment No. 3, cotton-seed meal in No. 4), to determine what effect, if any, these feeds might have on the digestibility of the prickly pear, or vice versa. In experiment No. 5 the digestibility of the alfalfa, which was fed with prickly pear in experiment No. 3, was determined. The digestibility of the cotton-seed meal when fed alone was not determined as was done with alfalfa, it being decided to accept the digestion coefficients secured by other experiments for this feed. Summarized, the experiments were made to determine (1) Digestibility of prickly pear (Opuntia lindheimeri). (2) Digestibility of prickly pear (0. 7a?vis?). (3) Digestibility of prickly pear (0. engelmannii cyclaid-es) and alfalfa. (4) Digestibility of prickly pear (0. engelmannii cycloid fs) and cotton-seed meal. (5) Digestibility of a fair quality of second-cut alfalfa. DESCRIPTION OF THE STALLS. A good idea of the stalls used in these experiments may be obtained from figure 1. They were made of proper length and breadth so that the steers could lie down comfortably, but not wide enough to permit them to turn around. The stalls used at the college were about 8^ feet long and 4 feet wide. Most of the floor, which had a slight inclina- tion from both front and rear to vard the center and to one side of the stall, was covered with thick rubber cloth. The inclination of the floor allowed all the urine to run to the middle of the stall, where it was caught in a galvanized iron trough and conducted to vessels out- side the stall, as shown in the illustration. The urine trough ran the entire width of the stall near the center and just beneath the floor. A narrow 1-inch strip was nailed across the floor of the stall in such a manner as to prevent any liquid feces from running into the urine 16 DIGESTIBILITY OF PRICKLY PEAR BY CATTLE. trough. The side and back walls of the stalls were lined with gal- vanized iron wherever there was any danger from spattering of feces. The feed trough was made perfectly tight, and so placed that the animals could eat with comfort and not waste their feed. The stalls were covered and placed in a position to make the animals as com- fort able as possible. FIG. 1. The stalls used in experiments Nos. 2 to 5. THE FEEDING. The preliminary feeding period which preceded the experiment proper was never less than seven days, usually more. In this time there was little possibility of any other food being left undigested in the animals' systems. The steers were then placed in the stalls and a weighed amount of the feed was given them twice each day, a sample being reserved for analysis each time before weighing. The prickly pear was first prepared by singeing the spines by means of a brush fire and chopping the singed stems into small pieces with a large knife or root chopper. A quantity of this feed was kept before the animals most of the time for a period of five days, the refuse being removed and weighed twice each day. METHOD OF COLLECTING THE EXCRETA. 17 COLLECTING THE FECES. After the preliminary period of a .week or more the steers, which during this time had the run of a small inclosure, were placed in their stalls, but the feces were not collected for twenty-four hours afterwards. This was assumed to be the feces from the first feed that was weighed to them the day before. While this is an unsatisfactory method of determining the first weighed feed, it seemed the best that could be done, and it is believed that the error resulting, if any, was not large when the sum of the feces for the five days was taken. It is a difficult matter to mark the beginning of a digestion experiment with steers. In experiments of this kind with man or animals other than ruminants it is customary to use charcoal or some indigestible material of a dif- ferent color from the feces, which will give a distinct line of separation between feces from weighed and unweighed food, but with the steers the marking of the weighed feed was not so simple. The experi- ment was tried of giving a small handful of weighed uncrushed corn as recommended in Minnesota Experiment Station Bulletin 99, but the method was found unsatisfactory in this instance because at times the corn did not appear for three or four days, and then it did not all come together. Usually in digestion experiments with animals it is customary to fasten rubber bags to them by means of a harness to catch the excreta, but this was wholly impracticable with any range steers that could be obtained. Hence it was necessary to arrange the stalls as well as we could for the separation of feces and urine, and to keep an attend- ant constantly with the steers during the entire experiment. The work was made unusually difficult because the steers were wild and somewhat nervous all the time. Then, too, as the prickly pear caused diarrhea or "scouring" in the animals, extra care had to be exercised to prevent loss of feces from spattering and otherwise; but it is believed that with the precautions taken the method used was quite as satisfactory as the method of collecting in bags. COLLECTING THE URINE. Since the digestibility of a food is shown by the difference between the amount eaten and the amount undigested, all of which is found in the feces, there can be no object in collecting the urine when the digestibility of the food is all that is sought. This is therefore collected only when it is desired to know something of the metab- olism of the nitrogen of the food. The solid matter of urine other than the inorganic salts is principally urea and other highly nitroge- nous compounds resulting from awaste of muscular and other nitrog- enous tissue, the kidneys being the principal organs through which 34749 Bull. 10n 08 3 18 DIGESTIBILITY OF PRICKLY PEAR BY CATTLE. this waste is excreted from the body. The excess of nitrogenous mutter from the digested proteids of the food may also be found in the urine. In the experiments the urine was collected, weighed, and analyzed for the purpose of studying the income and outgo of nitrogen with the different feeds, in some of which the proteids were present in very small amounts, while in others the nutritive ratio was much narrower than that given by Wolff for oxen at rest in stalls. The results of this study of nitrogen metabolism are given in Table 17, and are discussed under "Income and outgo of nitrogen" in another part of this bulletin. PREPARATION OF THE SAMPLES. Samples of the feed and refuse were collected twice daily, and of feces and urine once each day. After a moisture determination had been made on the samples of feed and refuse for each day the dry matter from them all was mixed for one composite sample. The daily samples of feces and urine were analyzed separately in all experiments except for the urine in experiment No. 1. In this instance one composite sample was made of all daily samples. In collecting the samples of feed, refuse, and feces about 200 grams of the fresh material were taken in a large porcelain dish and placed in the hot New Mexico sun where it soon reached an air-dry condition. The dry material was then pulverized and was ready for the analyses, which were made according to the methods of the Association of Official Agricultural Chemists. REPORT OF THE EXPERIMENTS. EXPERIMENT No. 1. DIGESTIBILITY OF PRICKLY PEAR (Opuntia lindheimeri). This experiment was conducted at the ranch of Mr. Alexander Sin- clair, near San Antonio, Tex. This locality was selected because in that section the prickly pear grows much more luxuriantly than it does in the vicinity of the Ne'w Mexico Agricultural College, and cat- tle there are more accustomed to eating the plant than are the cattle of New Mexico; in fact, the steers that were fed at the college had to be trained to eat prickly pear, and in consequence ate not more than half the amount eaten by the Texas steers. Moreover, during part of the tune, at least, what they did eat was little relished, except when fed in connection with some other feed. In this experiment two 3-year-old range steers, weighing about 800 pounds each, were used. They were fed for a preliminary period of ten days before being placed in the stalls. The experiment began at noon January 2, 1906, and continued until noon of January 6. The DIGESTIBILITY OF PRICKLY PEAR ALONE. 19 steers were placed in a barn with plenty of light and air, and were well protected from the cold. They remained in good condition dur- ing the entire experiment, except that they scoured quite badly, as animals always do on an exclusive prickly pear diet. The fact that these animals scoured is not surprising when one considers that in eating 100 pounds of prickly pear, the average daily ration during the five days, they consumed 2.95 pounds of inorganic matter or ash, which doubtless means more than twice this amount of salts more or less purgative in their character. The steers also obtained 86.4 pounds (or over 10 gallons) of water from 100 pounds of prickly pear, and this would doubtless aid the salts in their purgative action. The water obtained from the feed was more than was drunk by the steers in experiment No. 5 where alfalfa alone was fed and in which an average of only 48 pounds a day was drunk. The steers in experi- ment Xo. 1 took no water during the experiment except that obtained from the feed. In Table 3 is given the composition of the composite sample made up of daily samples of the pear fed and refused during the four days the animals were in the stalls. There are also given analyses of daily samples of the feces from both steers. From the'se figures with the weights of the dry matter in feed and feces have been calculated the data given in Table 4. TABLE 3. Experiment Xo. 1 Composition of the prickly pear fe 73. 18 pear, wnt water free r fre" ... . . Steer No. 1. 1 Steer No. 2. J" 22 DIGESTIBILITY OF PRICKLY PEAR BY CATTLE. TABLE 5. Experiment Xo. 2 Composition of the prickly pear fed, of the refuse, and of the feces Continued. Water. FPCCS of steor No. 1: First day Second day Third day Fourth day Fifth day Feces of steer No. 2: First day Second day Third day Fourth day Fifth day Perrtnt. 76.72 75.40 74.55 72.04 82.50 81.04 80.01 84.46 76. 69 Ash. Protein. Fat. Crude fiber. Nitrogen- free extracts Organic matter. Per cent. Per cent. Percent. Percent. Per cent. Percent. 38.85 6.98 1.33 18.94 33.90 61.15 44.49 6.87 1.28 19.22 28.14 55.51 38.62 7.42 1.51 21.64 30.81 61.38 31.74 8.49 1.77 20.07 37.93 68.26 31/42 6.81 1.95 24.52 35.30 68.58 37.07 7.28 1.49 21.38 32.78 62.93 41.75 5.78 1.16 21.07 30.24 58.25 40.01 5.91 1.40 19.82 32.86 59.99 31.32 5.91 1.54 19.56 41.67 68.08 36.86 6.91 1.98 24.57 29.68 6.1.14 TABLE 6. Weight of the feed, refuse, and feces in experiment Xo. ^, with the calculated digestion coefficient. STEER NO. 1. Dry matter. Ash. Protein. Fat. Crude fiber. Nitrogen- free extract. Organic matter. Total prickly pear fed tirniit*. 18 749.3 Grams. 3,946.7 Grams. 791.2 Grams. 320.0 Grams. 3 114 3 Grams. 10, 576. 5 Grams. 14 802 Total prickly pear refused 3,694.5 806.1 171.4 53.9 633.2 2,029.9 2,888.4 Total prickly pear eaten. 15,054.8 3,140.(i 619.8 206.7 2.481.1 8,546.6 11,914.2 Feces: First day. 912.6 354.5 63.7 1ZO 172.8 309.5 558 1 Second day . . ... 1,287.8 572.9 88.5 16.5 247.5 362.4 ' 714.9 Third day 090.0 206.5 51.2 10.4 149.3 212.6 423.5 Fourth day 917.5 291.2 77.9 16.2 184.1 348.1 626.3 Fifth day 1,382.1 434.3 94.1 27.0 339.0 487.7 947.8 Total feces dropped 5. 190. 1,919.4 375.4 82.2 1,092.7 1,720.3 3,270.6 Total digested. . 9,684.8 1,221.2 244.4 184.5 1,388.4 6,826 3 8 643 6 Coefficient of digestion (per cent) ... 15.52 38.88 39.43 69.18 55.90 79.87 72.55 STEER NO. 2. Total prickly pear fed 23, 753. 8 5,000.2 1,002.4 406.2 3,945.5 13 399 5 18 753 6 Total prickly pear refused 2,530.0 552.0 117.4 " 36.9 433.6 1,390.0 1,978.0 Total prickly pear eaten. 21,223.8 l.-l-IVJ 885.0 369.3 3,511.9 12.009.5 16,675.0 Feces: First day 1,554.5 576.3 113.2 23 2 332.3 509 5 978 2 Second day 1,784.1 744.9 103.1 20 7 375.9 539 5 1 039 2 Third day 1,228.0 491.3 72.6 17.2 243.4 403.5 736 7 Fourth day.. 1 434.3 449 2 84.8 22 1 280 5 597 7 985 1 Fifth day 1,981.4 730.3 136.9 39.2 486.8 58812 1,251.1 Total feces dropped 7,982.3 2,992.0 510.6 122.4 1,718.9 2 038.4 4 990 3 Total prickly poar digested Coefficient of digestion (per cent) 13,241.5 62.40 1,456.2 32.74 374.4 42.31 246.9 68.86 1,792.0 51.02 9,371.1 78.03 11,785.3 70 12 Average coefficient of digestion . 63.96 35.81 40.87 69.02 53.99 78.95 71.39 DIGESTIBILITY OF PRICKLY PEAK AND ALFALFA. 23 EXPERIMENT No. 3. DIGESTIBILITY OF PRICKLY PEA.n(Opuntiaengelmanniicycloides) AND ALFALFA. Since prickly pear will not furnish a balanced ration when fed alone, but requires some feed of a relatively high protein content as a supplement, the effect of alfalfa on the digestibility of the prickly pear has here been tried. Steer No. 1 was given an average of 4.5 pounds of alfalfa daily, while 4.72 pounds was given to steer No. 2. In addition they were given all the prickly pear they would eat, which was 42.16 pounds for steer No. 1, and 57.18 pounds for steer No. 2. The prickly pear used was Opuntia engelmannii cycloides, which is a larger stemmed plant than most of the native prickly pears, and the animals seemed to relish it better than they did O. Isevisf, the variety used in the preceding experiment. The results obtained in feeding this ration to steer No. 1 were for some unaccountable reason very unsatisfactory. The dry mat- ter digested amounted to- only 56.81 per cent and the ash to 16.87 per cent, while the protein coefficient was minus 16.54 per cent. This negative value for protein means that the protein of the feces amounted to more than that of the feed, which, of course, is an error. Whether this was due to blood or cleavage products in the feces, we can not say. The percentage of nitrogen in the feces was unusually high, but duplicate analyses of these were made that checked within reasonable limits of working error. Only 29.92 per cent of the fiber was digested by this animal, but the amounts of fat, nitrogen-free extract, and organic matter seemed to compare favorably with the coefficients of these nutrients from the feed of steer No. 2. Assuming the digestibility of prickly pear fed in this experiment to be an average of the coefficients for the two varieties determined in experiments Nos. 1 and 2, we have by the use of this factor calculated the digestion coefficient of the alfalfa that consti- tuted the other .portion 'of the ration. The coefficients obtained for alfalfa with steer No. 1 are quite as unsatisfactory as were those obtained from this steer for prickly pear. They Avere all far below the normal digestion coefficients for this feeding stuff, the results for ash being minus 38.9 per cent. While the results obtained from steer No. 1 with this ration are all recorded in the following tables, it is very evident that the coefficients found can not be used in the calculation of rations of either prickly pear or alfalfa. We have therefore omitted them from all averages. With steer No. 2 the results show an increase in the digestibility of the nutrients of both feeds, and this is just what might be expected with this ration. For a comparison of the digestion coefficients of prickly pear and alfalfa obtained in the following table with those of prickly pear obtained in the other experiments and of alfalfa obtained both here and at the other experiment stations, see Table 14. 24 DIGESTIBILITY OF PRICKLY PEAR BY CATTLE. TABLE 7. Experiment No. 3 Composition of the prickly pear an>l alfalfa fed, of the refuse, and of thefeces. [Nutrients reported water free.] Water. Ash. Protein. Fat. Crude liU-r. Nitrogen- free ex- tract. Organic matter. Per cent. None. None. Percent. 18.75 10.09 18.75 None. 35.62 27.87 29.46 26.85 25.80 29.65 27.40 28.71 23.84 28.10 Per cent. 2.98 14.09 2.98 None. 7.00 9.80 9.42 9.01 9.10 7.40 8.20 8.24 7.13 7.09 Per cent. 1.48 2.07 1.48 None. 2.02 1.93 2.18 1.87 1.50 1.91 1.80 1.82 1.76 1.64 Per cent. 12.22 32.28 12.22 None. 25.79 32.68 20.62 28.00 29.65 36.80 27.71 26.00 29.18 31.83 Per cent. 64.57 41.47 64.57 None. 28.97 27.72 38.32 34.27 33.95 24.04 34.89 35.23 38.09 31.34 Per cent. 81.25 89.91 81.25 None. 64.38 72.13 70.54 73.15 74.20 70.35 72. 60 71.29 76.16 71.90 Mfalfa water free Refuse of prickly }>ear, steers \os. 1 and 2. Refuse of alfalfa, steers Nos. 1 a nd - None. 73.56 82.79 80.89 80.10 79.02 82.00 83.67 80.88 83.13 83.46 Feces of steer No. 1 : First day Third day Fourth day.. Fifth day Feces of steer No. 2: First day Second day Third day ... Fourth day Fifth day TABLE 8. Weight of the feed, refuse, and feces in experiment No. 3, with calculated digestion coefficients of both feeds used and of each separately. STEER NO. 1. Dry matter. Ash. Protein. ! Fat. Crude filx-r. Nitrogen- free ex- tract. Organic matter. Total pricklv pear fed Grams. Grams. 33,994.7 6,374.0 14.226.6 2.660.4 Grams. Grams. 1,012.0 503.1 424.3 210.7 Grama. 4. 154. 1 1.739.7 Grams. 21,950.4 9, 192. 6 Gram*. 27,620.7 11,567.2 Total prickly pear refused Total prickly pear eaten. 19.758. 1 3,704.6 j 587.7 i 292.4 12.414.4 12,757.8 | 15, 053. 5 Total alfalfa fed 9,685.6 977.3 1,364.7 200.5 3, 126. 5 4, 016. 6 8, 708. 3 Total ulfalfa refused None None. None None None. None None. Total alfalfa eaten 9. 685. 6 977.3 i 364.7 ' 200.5 3, 126. 5 4.016.6 8. 708. 3 Feces: First day 2 164.9 771. 1 164.5 43.7 558.3 627. 3 1 393.8 2 502 2 722 4 254 50' 847. 1 718 7 1 809 8 Third day 2 062 607.5 194.2 45.0 425.2 790. 1 1, 454. 5 Fourth day 2 980 800.1 ,. 55.7 834 4 1 021.2 2, 179. 9 Fifth day 3. 008. 5 776.2 273.8 45.1 892.0 1,021.4 2, 232. 3 Total feces dropped Coefficient of digestion of prickly pear and alfalfa (per cent) 12,807.6 56.84 3,677.3 21.46 1,155.0 40 84 239.5 51 41 3,557.0 35.80 4,178.8 75.09 9, 130. 3 61.57 Total alfalfa undigested Total feces from prickly pear. . Total prickly pear digested Coefficient of digestion of prickly pear (percent). 4,273.3 8,534.3 11,223.8 56.81 597.6 3,079.7 -624. 9 16.87 470.1 694.9 -97.2 16.54 163.4 76.1 216.3 73.97 1,865.0 1,692.0 722.4 29.92 1,211.4 2, 967. 4 9, 790. 4 76.74 3,675.8 5,454.5 9,599.0 63.09 Coefficient of digestion of al- falfa (per cent) " 39. 35 38.90 29.76 26.54 26.65 57.04 42.24 a Calculated on the assumption that the coefficient of digestion of the prickly pear used in this experi- ent was an average of the two varieties fed in experiments Nos. 1 and 2. PRICKLY PEAR AND COTTON-SEED MEAL. 25 TABLE 8. Weight of the feed, refuse, and feces in experiment No. 3, v:ith calculated digestion coefficients of both feeds used and of each separately Continued. STEER NO. 2. nSSr. A*. Protein. Fat. Crude *SP ma g t a ter C Total prickly pear fed Grams. 39, 146. 1 Grams. 7,339.9 Grams. 1 166.6 Grams. 579.4 Grams. 4 783 7 Grams. 25 276 4 Grams. 31 806 2 Total prickly pear refused 12,033.3 2. 256. 2 358.6 178.1 1,470.5 7, 769. 9 9, 777. 1 Total prickly pear eaten . 27,112.8 5.083.7 80,8. 401.3 3,313.2 17, 506. 5 22. 029. 1 Total alfalfa fed 10, 157. 3 1, 024. 9 1,431.2 210.2 3 278 8 4 212. 2 9 132 4 Total alfalfa refused None. None None Total alfalfa eaten 10, 157. 3- 1,024.9 1,431.2 210.2 :i,2rs. ,s 4, 212. 2 9, 132. 4 Feces: First day 1,948.5 577.7 144.2 37.2 717.0 472 4 1 370 7 Second day 2, 604. 6 713.7 213.6 46.9 721. 7 908.7 1 890 9 Third dav . . . 2,820.2 809.7 232.4 51.3 733.3 993.5 2 010 5 Fourth day 3, 188. 4 760.1 227.3 56.1 930.4 1,214.5 2 428.3 Fifth day 2 160 1 607.0 153.2 35.4 687 6 676 9 1 553 1 Total feces dropped 12, 721. 8 3,468.2 970.7 226.9 3,790.0 4.266.0 9, 253. 5 Coefficient of digestion of prickly pear and alfalfa (per cent) 65.87 43.22 56.65 62.89 42. 51 SO.S6 70.34 Total alfalfa undigested Total feces from pricklv pear 4,481.3 8, 240. 5 626.7 2,841.5 493.0 477.7 147.2 79.7 1,955.8 1,834.2 1,270.4 2, 995. 6 3,854.8 5, 398. 7 Total prickly pear digested Coefficient of digestion of pricklv pear (percent). . 18, 872. 3 69.61 2,242.2 44.11 189.3 40.88 321.6 80.14 1, 479. 44.63 14,510.9 82.88 16,630.4 75.49 Coefficient of digestion of al- falfa (per cent) 68.41 80.59 60.65 52.28 37. 29 78.65 64.38 EXPERIMENT No. 4. DIGESTIBILITY op PRICKLY PEAR (Opuntiaengelmanniicycloides) AND COTTON-SEED MEAL. In the prickly-pear region of Texas a ration consisting of this feed- ing stuff with cotton-seed meal is very common. It is customary and better to give the cattle either the run of a dry grass pasture or some coarse feed in connection with this ration, as it will serve the double purpose of widening the too narrow ration produced from too much cotton-seed meal and tend to check the scouring which results from the use of these two feeds alone. Bulletin 74 of the Bureau of Plant Industry, United States Department of Agriculture, gives a num- ber of rations as used by Texas stockmen and dairymen made up of prickly pear and cotton-seed meal in varying amounts that were usually fed together with other feeds. However, in the ration used in this digestion experiment prickly pear and cotton-seed meal alone were used, because it was desired not only to determine the coefficient of digestion of the ration of the two when fed together but also to use the weights obtained for a calculation of the coefficient of diges- tion of cotton-seed meal, and these would have been complicated by the addition of other feeds to the ration. 26 DIGESTIBILITY OF PRICKLY PEAR BY CATTLE. Steer No. 1 ate an average of 4.78 pounds of cotton-seed meal and 37.28 pounds of prickly pear daily. This made only 14.14 pounds of dry matter, which was about 1 pound short of a maintenance ration of dry matter; but the proteids were in excess of the amount required for maintenance by more than a pound, and while the carbohydrates were a trifle short the excess of both proteids and fat made the total nutrients more than the amount required for maintenance. The nutritive ratio of the feed for this steer was 1 to 4.49, and he gained 1,551.9 grams of proteids in the five days. Steer No. 2 ate a daily average of 4.99 pounds of cotton-seed meal and 47.04 pounds of prickly pear. This gave him 17.35 pounds, or nearly 1 pound more than a maintenance ration, of dry matter which contained a slight excess of all the nutrients. The nutritive ratio of his feed was 1 to 5.52. He gained for the five days 1,262.5 grams of protein. The digestion coefficient for the two steers agreed very closely, but while the coefficient for the protein of cotton-seed meal and of cotton-seed meal with prickly pear was about what might be expected, the coefficient for the protein in the prickly pear was a minus quan- tity to about the same degree for both steers. This error might be attributed to several causes. It may have been because the composite sample of pear used for analysis did not contain sufficient proteids to be representative of the prickly pear fed. It had only 2.59 per cent of protein, while an average of the five samples of this species recorded in Bulletin 60 of the New Mexico Experiment Station had 3.99 per cent, and an average of all prickly pears contained 4'.47 per cent protein in the air-dry material. It is barely possible also that some error may have been introduced here by hairs from the shedding animal getting into the feces. It is also possible that it resulted from a larger amount of metabolic products formed from a feed like cotton-seed meal with its high protein content. Steer No. 1, for example, got hardly 1 pound of protein from the prickly pear during the five days, but obtained nearly 10.5 pounds from the cotton-seed meal; and the large amount of protein from the latter source may have increased the metabolic nitrogen in the feces and thus made it appear that the feces from the prickly pear con- tained more protein than did the. feed, when in reality it may have been due in part at least to cleavage products resulting from the protein of the cotton-seed meal fed. As a further attempt to explain these negative results Professor Spillman has suggested the very probable theory that it resulted from the reduced digestibility of the protein of the cotton-seed meal, due to the laxative action of the prickly pear forcing the other feed from the digestive tract before its protein, which digests slowly, had been thoroughly acted upon, but not before the easily digested COMPOSITION OF PRICKLY PEAR AND COTTON-SEED MEAL. 27 carbohydrates had been more completely assimilated. Since cotton- seed meal is a substance rich in protein and the prickly pear is very poor in this ingredient, a very slight reduction of the digestion coef- ficient of the former would and did result in an apparent negative result for the latter. The average of three digestion coefficients for cotton-seed meal as given in Bulletin 77 of the Office of Experiment Stations, United States Department of Agriculture, was used in calculating these coefficients. Since the cotton-seed meal used in this experiment was adulterated with hulls, as may be seen from the crude-fiber analysis, it may be that the figures from the above bulletin did not represent the coefficients for the meal used in the experiment. If, however, we assume the digestibility of prickly pear fed to be the same as that obtained in previous experiments, and calculate the coefficients of digestion for the nutrients of cotton-seed meal accordingly, we find them somewhat similar to those given in Bulletin 77. It is inter- esting to note that both of our calculations show over 100 per cent of the fat digested, which agrees with some of the results recorded in the above bulletin, and substantiates also the statement made by Jordan in his work on "The Feeding of Animals" that "pure vegetable fats and oils are quite completely emulsified and absorbed" by animals. . TABLE No. 9. Experiment No. 4 Composition of the prickly pear and cotton-seed meal fed, of the refuse, and of the feces. [Nutrients reported water free.] Water. Ash. Protein. Fat. Crude fiber. Nitrogen- free ex- tract. Organic matter. I'rickly pear, water free Per cent. 72.97 Per cent. 21.74 Per cent. 2.59 Per cent. 2.03 Per cent. 11.44 Per cent. 62.20 Per cent. 78.26 5.09 6.68 44.25 10.02 11.02 28.03 93.32 Refuse of prickly pear, steer No. 1 21.89 2.85 1.25 'l2. 26 61.75 78.11 Refuse of prickly pear, steer No 2 24.87 2.85 1.51 11.38 59.39 75.13 Refuse of cotton-seed meal, steers Nos 1 and 2 6.68 44.25 10.02 11.02 28.03 93.32 Feces of steer No. 1 : First day 77.53 30. 45 ia09 .28 19. 13 36.05 69. 55 Second day 82.51 30.85 12.85 .55 18.00 36. 75 69. 15 Third day 82.08 31.7(i 12.92 .18 18.12 36.02 68.24 Fourth day 82.63 34.82 12.14 .13 20.14 31.77 65. 18 Fifth day 79.58 35.09 11.38 .03 19.83 32.67 (14.91 Feces of steer No. 2: First day 81.08 26.21 14.76 .71 21. 62 35.70 73. 79 Second day 81.94 30.69 13.38 .29 19.93 34. 71 69.31 Third day 84. 13 31.78 14.22 .97 16.93 36.10 68.22 Fourth day.. . . . . . 82.75 36. 10 9.95 .05 22.04 30.86 (13.90 Fifth day 85. 15 34. 70 9.86 .Of, 19. 45 34. 93 (15. 30 28 DIGESTIBILITY OF PRICKLY PEAR BY CATTLE. T.UU.K N<>. 10. Wright ofthefeed, nfmtr, andfrcfg in experiment No. 4. with calculated diyt'stion coefficient* of liuth feed* used and of each separately. STEER NO. 1. Dry matter. Ash. Protein. Fat. Crude fil-er. Nitrogen- free ex- tract. Organic matter. Total prickly pear fed Grams. 29, 7 1 ". 2 Grams. 6 461.6 Grams. 709.8 Grams. 603.4 Grams. 3 400.2 Grams. 18 487.2 Grams. 23, 260. 6 Total prickly pear refused 7, 964. 5 1 . 743. 4 227.0 99. G 976. 4 4,918. 1 6,221. 1 Total prickly pear eaten. 21,757.7 1 7 ^ J 542.8 503.8 2, 423. 8 13,509.1 17, am 5 Total cotton-seed meal fed Total cot ton-seed meal re fused. 10, 758. 469.8 71" (, 31.4 4,7fi0.4 207.9 I.!l7s II 47.1 1,185.5 51.8 3,015.5 13I>6 10,039.4 438.4 Total cotton-seed meal eaten I0.2SS .' G87.2 4,552.5 1,030.9 1,133.33 2,883.9 9,601.0 Feces First day '2, 033. 5 i.l'i 206.2 26.0 389.0 I'M \ 1,414.3 Second day 436. 8 751 8 313.1 37.8 438.6 895.5 1,685.0 Third day 1,803. 7 591.9 240.8 22.0 337.7 671.3 1,271.8 Fourth day 1 544.2 537.7 187.5 17.4 311.0 490.6 1,006.5 Fifth day 550 5 SO") 290.2 26 3 505. 8 833.2 1,655.5 Total feces dropped 10. 428. 7 3, 395. 6 1,297.8 129.5 1 , 982'. 1 3, 623. 7 7,033. 1 Coefficient of digestion of prick- ly pear and cotton-seed meal (per cent) .. (17. 46 39.03 74. 53 91.56 44.28 77.97 73.60 Total cotton-seed meal undi- gested . . O "Q^ g 524. 3 528.1 (19.1 504.3 1,136.3 2, 294. 6 Total feces from prickly pear". . Total prickly pear di"ested. . 7 722. 9 H.rtM. 8 2,871.3 1.846.9 709.7 -226.90 60.4 443. 4 1, 477. 8 946.8 2,487.4 11,081.7 4,738.5 12,301.0 Coefficient of digest ion of prick- ly jiear (percent) tit. 50 39.01 -41. S '88.08 39. 03 81.67 72.19 Coefficient of digestion of cot- ton-seed meal (percent)'' ... 72.84 47.42 77. 51 102 7 .'{7.04 64.83 75.09 STEER NO. 2. Total prickly pear fed 35, 878. 3 7, 799. 9 929.2 728.3 4, 104. 5 22,316.4 28,078.4 Total prickly pear refused 7,279. 1 1,810.3 207.5 109.9 828.4 4,323.0 5, 468. 8 Total prickly pear eaten. 28.599.2 5,988.6 721.7 1,1", 1 3, 276. 1 17.'":;. 1 22,609.6 Total cotton-seed meal fed 10, 758. 718.6 4,760.4 1,078.0 1,185.5 3.015.6 10,039 :. Total cotton-seed meal refused . 20. 9 1.4 9.2 2.1 2.3 5.9 19.5 Total cotton-seed meal eaten . 10, 737. 1 717.2 4,751.2 1,075.9 1,183.2 3,009.7 10,020.0 Feces First day 1.296.1 339.7 191 3 22.2 280.2 462.7 950.4 Second day. 2,975.4 913.2 398. 1 38.4 593. 1,032. 7 2, 062. 2 Third day 2,487.6 790.6 353 7 24. 1 421.2 898.0 1,697.0 Fourth day 3,073.1 1,109.4 305.8 32.3 677.3 948.3 1,963.7 J Fifth day i 2,690. 1 . 933. 5 265 2 28.5 523.2 939.7 1,756.6 Total feces dropped 12, 522. 3 I.IIMi t 1,514. 1 145. 5 J. I'M " I.L'M. 1 8, 435. 9 Coefficient of digestion of prick- ly pear and cotton-seed meal (percent)... 68. 17 39.05 72.33 91.41 44.05 77.97 74.15 a Calculated on the Assumption that the digestibility of this variety of cactus was the average of the two fed in experiments Nos. 1 and 2. ft Coefficient of digestion for cotton-seed meal used in these calculations was taken from Bulletin 77, Office of Experiment Stations. I'nited States Department of Agriculture. DIGESTIBILITY OF SECOND-CUT ALFALFA. 29 TAF.LE No. 10. Weight of the feed, refuse, andfeces in experiment No. 4, with calculated digestion coefficients of both feeds used and of each separately Continued. STEKR NO. 2 Continued. Dry matter. Ash. Protein. Fat. Crude fiber. Nitrogen- free ex- tract. Organic matter. Average coefficient of digestion Grams. Grams. Grams. Gra/n*. Grams. Grams. ' Grams. of prickly pear and cotton- seed meal 67.82 2, 823. 9 9, 698. 4 39.04 547.2 3,539.2 73. 43 551.1 963.0 91.49 72.1 73.4 44.17 526. 5 1,968.4 77.97 1, 185. 8 3,095.6 73.88 2, 394. 8 6,041.1 Total cotton-seed meal undi- gested Total feces from prickly pear. Total prickly pear digested 18,900.8 2, 449. 4 -241.3 545.0 1,307.7 .14,897.8 16, 568. 5 Coefficient of digestion of prick- ly pear (percent) 66.08 40.90 -34.82 88.13 39.92 82.79 73. 28 Average coefficient of digestion of prickly pear (per cent) 65.29 3!). 96 -38.31 88.11 3t>. 4S 82. 23 72.74 Coefficient of digestion of cot- ton-seed meal (per cent) b . . . 76.88 67. 22 69.89 104. 6 34.06 72.71 I 77.28 Calculated on the assumption that the digestibility of this variety of cactus was the average of the two fed in experiments Nos. 1 and 2. ft Coefficient of digestion for cotton-seed meal used in those calculations was taken from Bulletin 77, Office of Experiment Stations, United States Department of Agriculture. EXPERIMENT No. 5. DIGESTIBILITY OF A PAIR QUALITY OF SECOND-CUT ALFALFA. This experiment was made to determine the digestion coefficients of the alfalfa that was used in experiment No. 3. The results are given in Table 12, from which it will be seen that the coefficients obtained in this experiment are about the same as those determined by other experiment stations. For some of the nutrients the coeffi- cient is somewhat less than was obtained elsewhere. This may be accounted for by the fact that the hay used hail lost a considerable proportion of its leaves in curing, and the Colorado Experiment Sta- tion has shown that these are the most digestible portions of the plant. The dry matter eaten per day was somewhat less than a mainte- nance ration. The proteids were far in excess of the amount required, yet steer No. 2 lost, and steer No. 1 gained only a small amount of this nutrient, which shows that the excess of proteids was evidently used to serve the function of carbohydrates. TABLE 11. Experiment No. Composition of I lie alfalfa fed. of the refuse, and of the feces. [Nutrients reported water free.] \Vutr.r. Ash. Protein. Fat. tract. I'rr crnt. I'rr crnt. I'rr crnt. I'rr crnt. Per crnt. Prr crnt. Prr crnt. Alfalfa HS fed '..IK* 9..\X 13.37 1.96 30. 64 39.36 . 33 Alfalfa, water free lo.ti9 14.09 2.07 32.2s 41.47 S9.91 Refuse, water (roe. steer No. 1 ... 10.09 14.09 2.07 32. 2* 41.47 S9.91 Refuse, water free, steer No. 2. 10.09 14.09 2.07 32.28 41.47 89.91 DIGESTIBILITY OF PRICKLY PEAR BY CATTLE. TABLE 11. Experiment .Vo. 5 Composition of the alfalfa fed, nf the refuse, and of the feces Continued. Water. Ash. Protein. Fat. Crude fiber. Nitrogen- free ex- tract. Organic matter. Feces of steer No. 1 : First day Per cent. 78.27 Per cent. 13.31 Per cent. 11.50 Per cent. 2.17 Per cent. 44 52 Per cent. 28.50 Per cent. 86.69 Second day 78.09 11.35 10.53 2.11 42.73 33.28 88.65 Third day 75.75 14.1} 10.68 2.52 45.06 27.63 85.89 Fourth day 78.98 15. 80 10.67 3.00 41.19 29.34 84.20 Fifth day 77.24 10.55 11.74 3.16 42.02 32.53 89.45 Feces of steer No. 2: First day : 84.87 16.15 11.57 2.26 43.68 26.34 83.88 Second day 88.56 13.19 10.72 3.18 46.67 26.24 86.81 Third day 80.97 15.56 10.63 3.37 42.56 27.88 84.44 Fourth dav 81.82 15.41 11.57 3.51 43.37 26. 14 84.59 Fifth day 74.99 13.61 10.63 3 36 46 54 25 86 86 39 TABLE 12. Weight of the feed, refuse, and feces in experiment No. 5, with the. calculated digestion coefficient. STEER NO. 1. Dry matter. Ash. Protein. Fat. Crude fiber. Nitrogen- free ex- tract. Organic matter. Grams. Total alfalfa fed . . 32, 274. 1 Grams. 3,256.5 Grams. 4, 547. 4 Grams. 668.1 Grams. 10,418.1 Grams. 13,384.0 Grams. 29,017 li Total refused. 121.1 12.2 17.1 2.5 39.1 29.1 87.8 Total eaten 32,153.0 3,244.3 4,530.3 665.6 10,479.0 13 384 9 US > ! -, Feces: First day . 2,162.1 287.8 248.6 46.9 962.6 616.2 1,874.3 Second day . 2,952.4 335.1 310.9 62.3 1,261.6 982.5 2,617.3 Third day . 2,934.3 414.0 313.4 73.9 1,322.2 810.8 2, 520. 3 Fourth dav . 2,979.6 470.8 317.9 89.4 1 fy ^'t 3 874.2 2,508.8 Fifth day 2,981.6 314.6 350.0 94.2 1,252.9 969.9 2,667.0 Total feces dropped 14, 010. Total digested. 18,143.0 1,822.3 1,422.0 1,540.8 2,989.5 366.7 298.9 6,026.6 4, 452. 4 4,253.6 9,101.3 12, 187. 7 16, 742. 1 Coefficient of digestion (per cent) 56.43 43.83 65.99 44.91 42.49 68.15 57.87 STEER NO. 2. Total alfalfa fed 32,274.1 None. 3,256.5 None. 4,547.4 None. 668.1 None. 10, 418. 1 None. 13,384.0 None. 29,017.6 None. Total refused Total eaten 32,274.1 3,256.5 4,547.4 668.1 10,418.1 13,384.0 29,017.6 Feces: First day 2,258.2 1.947.1 2,816.4 3,245.1 4, 150. 4 364.7 256.8 438.2 0.1 564.9 261.3 208.7 299.4 375.5 441.2 51.0 61.9 94.9 113.9 139.5 986.4 908.7 1,198.7 1,407.4 1,931.6 594.8 511.0 785.2 848.2 1,073.2 1,893.5 1,690.3 2,378.2 2,745.0 3,585.5 Second day Third day Fourth day . . Fifth day Total feces dropped Total digested 14.417.2 17,856.9 55.33 2, 124. 7 1,131.8 34.75 39.29 1,586.1 2,961.3 65.12 65.56 461.2 206.9 30.97 37.94 6,432.8 3.985.3 38.20 40.35 3, 812. 4 9,571.6 J1.S2 69.84 12,292.5 16, 725. 1 57.63 57. 75 Coefficient of digestion (per Average coefficient of digestion (per cent) 55.88 AVERAGE DIGESTIBILITY OF RATIONS USED. 31 EFFECT OF PRICKLY PEAR OX THE DIGESTIBILITY OF OTHER FEEDING STUFFS- From Table 13 it may be seen that in feeding a mixed ration of prickly pear and alfalfa, or prickly pear and cotton-seed meal, the general effect is to increase the digestibility of all three feeds. This table shows an increase in the digestible dry matter of all three, and with some exception there is an increase in the digestibility of the nutrients in them all. If the ration of prickly pear will increase the digestibility of all feeding stuffs, as it apparently has that of alfalfa and cotton-seed meal, then this feed has a greater value than is shown by its own digestible nutrients. The probabilities are that the addition of this green and succulent feed to any dry feeding stuff will increase the digestibility of both. TABLE 13. Average digestibility of prickly pear, alfalfa, and cotton-seed meal, and of a mixed ration of alfalfa and prickly pear, and cotton-seed meal and prickly pear. Dry matter. Ash. Protein. Fat. Crude fiber. Nitrogen- free ex- tract. Organic matter. Prickly pear alone . Per cent. 64.91 Per cent. 35.69 Per cent. 49.56 Per cent. 68.46 Per cent. 47.66 Per cent. 80.77 Per cent. 72.76 Alfalfa alone 55.88 39.29 ' 65.56 37.94 40.35 69.84 57.75 Cotton-seed meal alone 73.70 23.70 88.40 93.30 55.50 60.60 76.10 Alfalfa and prickly pear 68.41 80.59 60.65 52.28 37.27 78.65 64.38 Cotton-seed meal and prickly pear 74.86 57.32 73.70 103.70 35.55 68.77 76.19 TABLE 14. Summary of all digestion coefficients obtained in these experiments, together with some coefficients of alfalfa and colton-sced meal as determined elsewhere. Feed. Steer No. Dry matter. Ash. Pro- tein. Fat. Nitro- Crude gen- fiber, free ex- tract. Or- ganic matter. Prickly Pear (Opuntia lindheimeri) . . . Do 1 2 Per ct. 67.12 64.61 Per ct. 37.46 33.67 Per ct. 59.03 57.47 Per ct. 67.42 68.38 Per ct. Per ct. 41.31 83.40 41.32 81.78 Per ct. 71.21 77.03 Average b.5.86 :r.. :>7 :,\ _>.-, tiT.'.H) 41.32 82.59 74.12 Prickly pear (O. ten'*?) 1 i. .-..:._' 38.88 39.43 69.18 55.96 : 79.87 72.55 Do 2 62.40 32.74 42.31 68.86 51.02 78.03 70.12 Average 63.96 :{:, M 40.87 69.02 53.99 78.95 71.39 Averages of both above averages 64.91 35.69 49.56 68.46 47.66 ' 80.77 72.76 Prickly pear, calculated from feed of prickly pear and alfalfa >! "56.81 16.87 16.54 73.97 29.9-2 76.74 63.09 Do .... 2 69.61 44 11 40 88 80 14 44.63 82.88 75 49 Prickly pear, calculated from feed ol prickly pear and cotton-seed meal. . . Do... 1 2 64.50 65.29 39.01 39.96 -41.89 38.31 88.08 88.11 39.03 81.67 39.48 82.23 72. 19 72.74 Average j 64.90 39.49 1-40.60 88.10 39.26 81.95 72.47 o The digestion coefficients obtained from steer No. 1 that was fed a ration of prickly pear and alfalfa are all evidently too low and should not be used In the preparation ol rations from cither prickly pear. alfuHa, or the mixed feed. 32 DIGESTIBILITY OF PRICKLY PEAR BY CATTLE. TABLE 14. Summary of all diifeslion coefficients obtained in these e.r peri mentf, together trilh some coefficient* of alfalfa and cotton-seed meal as determined elsewhere Con. Feed. Steer No. Dry matter. Ash. Pro- tein. Fat. Crude fiber. Nitro- gcn- f roe ex- tract. Or- ganic matter. Prickly pear and alfalfa Per ct. 50.84 Per ct. 21.46 Per ct. 40.84 Per ct. 51.41 Per ct. 35.80 Per ct. 75.09 Per ct. 61.57 Ho 2 65.87 43.22 56.65 62.89 42.51 80.36 70.34 61.36 32.34 is. 7:, 57. !." 39.16 77.73 65 96 Prickly pear and cotton-seed meal. . . . Do 1 2 i,7. It, 68.17 30. 03 39. 05 74.53 72.33 91.56 91.41 44.28 44. 05 77.97 77.97 73.60 74.15 \verage . 67.82 :'.'.i in 7.:. :i VI I" 44.17 77 '17 73 88 Alfalfa alone 1 56.43 43.83 65.99 li.'.tl 42.49 68.15 57.87 Do 2 55.33 34.75 65.12 30.97 38.20 71.52 57.63 :,:, ss ;;,, ., 65.56 :<7 '.il in :>:, i,'i s( 57 75 Alfalfa when fed with prickly pear Do "1 o 39.35 68.41 38.90 80.59 .'.I.7., 60.65 26.54 52.28 26.65 37.29 57.04 78.65 4-J.24 64 38 A verage . ... 53. ss 59.75 45.21 39.41 .il !I7 1,7 s.-, .53 :;i Alfalfa, C'olorado K: vperiment Sta- tion. " 63. 95 57.67 72.54 29.86 49.93 72.89 Alfalfa:') Maximum CO. 20 40.90 77.00 54. 00 49.00 71.80 Minimum .... 57. 00 38.00 68.80 48.40 43.30 64.00 \verage 58 90 39 .50 72 00 51.00 46 00 69 20 Alfalfa, Minnesota Kxperiment Sta- tion .... 65.84 51.48 75.38 55.88 57.57 71.86 Alfalfa, Kansas Kxperiment Sta- tion: First cut 59.40 63.49 78. 52 60.00 46.10 75.31 Second cut 58.25 56 41 75.14 30.39 .50.44 71.99 Third cut 60.03 60 90 76.70 51.65 50.63 75.24 Alfalfa, Utah Kxperiment Station 60.16 40.85 70.30 50.57 45.67 71.80 Cotton-seed meal:& Maximum S3. 90 38 00 96.10 103.20 100.00 71.00 87.00 Minimum 65.00 3 00 83.50 87.30 19. 50 43.80 69. 10 Average. . 73.70 23.70 ss (I) 93.30 :,:, .vi 60.60 76.10 Cotton-seed meal from feed of cotton- seed meal with prickly pear Do 1 2 72.84 76.88 47. 42 67.22 77. 51 69.89 102. 7 104.6 37.04 34.06 64. S3 72.71 7.5.09 77.28 Average 71. sc, 57.32 W.70 103.7 :;:,.:,:, 68.77 76.19 a The digestion coefficients obtained from steer No. 1 that was fed a ration of prickly pear and alfalfa are all evidently too low and should not be used in the preparation of rations from either prickly pear, alfalfa, or the mixed feed. * Bulletin 77, Office of Kxperiment Stations, United States Department of Agriculture. SUMMARY OF THE FIVE DIGESTION EXPERIMENTS. 33 TABLE 15.- Daily rations fed during the fire digestion periods, and a maintenance ration for each steer calculated from Wolff's feeding standard for oxen at rest in stalls. STEER NO. 1. Experi- ment No. Feed. Digestible organic matter. Nutri- tive ratio. Dry matter. Protein. Carbo- hydrates. Fat. Total nutri- ents. 1 Prickly pear (Opuntia lind- heimeri) Pounds. 13.84 6.64 12.99 14.14 14.19 15.10 Pounds. 0.42- .11 .35 1.C8 1.31 .60 Pounds. 7.44 3.57 6.48 6.13 5. 98 6.90 Pounds. 0.13 .08 .11 .62 .11 .13 Pound*. 8.00 1:18.23 3.76 1:33.56 6.94 1:19.13 8.43 1: 4.49 7.40 1: 4.75 7.66 1 1:12 2 Prickly pear (O. Ixrisf). '. . . 3 Prickly pear and alfalfa 4. Prickly pear and cotton-seed meal 5 Alfalfa Maintenance ration STEER NO. 2. 1 Prickly pear (Opuntia lind- heimeri) 12.98 9.36 16.44 17.35 14.23 16. 70 0.40 .16 .56 1.75 1.32 .67 6.98 5.02 8.93 8.09 5. 98 7.65 0.13 .11 .17 .68 .11 .14 7.50 5.29 9.66 10.52 7.40 8.43 1:18.23 1:33.04 1:16.65 1: 5.52 1: 4.74 1:12 2 Prickly pear (0. Ixvisf) 3. Prickly pear and alfalfa 4.. Prickly pear and cotton-seed meal. Alfalfa Maintenance ration TABLE 16. Weight of feed eaten, feces and urine excreted, and water drunk during the five digestion periods. Ex- peri- ment No. Steer No. Weight of feed for five days. Feed. Average weight of Weight of feces for feed per day. five days. Grams. Pounds. Grains. Pounds. Grams. Pounds. ol 2 3 4 6 1 2 1 2 1 2 1 2 1 i Prickly pear (Opuntia lind- heimeri) 187,539 413.63 395.48 267.58 360.89 46,884. 75 44,828. 5 2,426.44 32,726 103.41 98.87 53.52 72.18 62,766 58,591 20,293 38,896 138.43 129.23 44.75 85.79 Prickly peai(O.Undheimeri) 179,314 Prickly pear (O. Jxvis^ ' 121, 322 Prickly pear (O. Ixris) 'l63,620 Pricklv pear 95 580 210.81 19,116 22.51 2,041 42.16 4 50 \lfiilf;i 10 05 Total 105,785 233.32 21,157 46.66 63,355 ],; :.: Pricklv pear 129 627 2.H5.89 23.60 25,925. 4 2,140.4 57.18 4.72 \lfalfa ^ 10,702 i Total 140,329 .m 49 28,065.8 61.90 73,485 162.07 Pricklv pear 84 498 186.36 2a92 16,899.8 2,169.0 37.27 4.78 Cotton-seed meal 10 845 Total 95,343 210.28 I'.l.nf.x s u or, 54.UI5 120 i; Prickly pear 106,645 235.21 21,329.0 24.% 2,263.6 17 HI 4.99 Cotton-seed meal 11 318 Total 117,963 260.17 23,592.6 52.03 75,155 165.76 Alfalfa 339, 922. 4 749. 72 750.0 67,984.5 68,010. 149. 94 160.0 62,800 81,190 138.51 179.07 Alfalfa 340,050 This experiment lasted for a period of four days only. 34 DIGESTIBILITY OF PRICKLY PEAR BY CATTLE. TABLE 16. Weight of feed eaten, feces and urine excreted, and water drunk during the five digestion periods Continued . Ex- peri- ment No. Steer No. Feed. Average weight of feces per day. Weight of urine for five days. Average weight of urine per day. Grams. Pounds. Grams. Pounds. Grams. Pounds. ol 2 3 4 5 , c i ; 1 2 1 2 1 J Prickly pear (Opunlia lind- heimeri) 15,691.5 14,647.75 4,058. 6 7,779.2 34.61 32.31 8.95 17.16 51,981 38,915 26,874 50,848 114.65 85.83 59.27 112.15 12,995.2 9,728.75 5,374.8 10,169.6 28.66 21.46 11.85 22.43 Prickly pear (O .lindheimeri) Prickly pear (O. Ixvist) Prickly pear (O.lsn>is) Pricklv pear Alfalfa Total 12,671 27.94 31,700 69.92 (1,34(1 13.118 Pricklv pear Alfalfa Total 14,697 32.41 42,222 '.1:1. u >,ltl 1 18.62 Prickly pear Cotton-seed meal Total 10,921 24.09 28,975 63.91 | 5,795 12.78 (Pricklv pear. Cotton-seed meal . Total 15,031 33.15 37,525 82.76 7,505 16.55 Alfalfa 12,560 16,238 27.70 35.81 44,785 43,910 98.77 96.84 8,959 8,782 19.75 19. 37 Alfalfa . ... Ex- peri- ment No. Steer No. Feed. Weight of water drunk for five days. Average weight of water per day. Grams. Pounds. Grams. - Pounds. ol 2 3 4 5 i ; I i 2 1 2 ! i Prickly pear (Opunlin lindhi Prickly pear (O. lindheimeri Pricklv pear (O. l&insf) imeri) . No ne. ne. 225 275 None. None. 37.99 27.07 None. None. 3.445 2,455 None. None. 7.00 5.41 ) . No 17. Prickly pear (O. Ixvts) 12, Pricklv pear. Alfalfa... Total 41,2(53 111.01 8,252.6 18.2 Prickly pear Alfalfa Total 43,240 95.37 S.04S 19.07 Cotton-seed meal Total 66,700 147. 11 13,340 29.42 Total 83,475 184.11 16,695 36.82 Alfalfa. . 106, 480 234.80 980 244. 77 21,296 22,196 46.97 48.95 Alfalfa... 110, 1 This experiment lasted for a period of four days only. GAIN OR LOSS OF NITROGEN. 35 INCOME AND OUTGO OF NITROGEN. In Table 17 is given the income and outgo of nitrogen for both steers during the five digestion periods. The gain or loss of nitrogen is the difference between the amount taken into the animal as food and the sum of that which is excreted in the feces and urine. It is interesting to note that in the first digestion period, when the steers were fed prickly pear (Opuntia lindheimen) alone which had a nutritive ratio of 1 to 18.23, they each gained nearly 1 pound of pro- teids in the four days. Steer No. 1, for example, ate 1,322.8 grams (2.9 pounds) of protein and gained 453.1 grams (1 pound) or 34.26 per cent. Prickly pear alone was the ration also for the second period, but in this experiment a different species was used, as well as different steers, and the latter were fat from a previous grain ration and not accus- tomed to eating prickly pear. Analysis shows that the feed from this species of prickly pear has about 1 per cent less protein than the species fed in the first period. The steers ate only about half the ration eaten by the steers for the first period and digested about 18 per cent less of the protein. As a consequence the nutritive ratio in this feed was 1 to 33 for both steers, and each lost over one-half pound of protein, or nearly 50 per cent of that eaten during their five-day digestion period. Steer No. 1, for example, consumed 99.2 grams and excreted 146.1 grams of nitrogen in the five days, making a loss of 293.1 grams (0.65 pound) of protein, or 47.28 per cent. In the third digestion period steer No. 1 ate 42.16 pounds of prickly pear and 4.5 pounds of alfalfa daily, while steer No. 2 ate 57.18 pounds and 4.72 pounds of alfalfa. Something went wrong in this experiment with either steer No. 1 or our analyses, we can not say which, although fairly closely agreeing duplicate determinations were secured in all the analyses. Table 17 shows a low digestion coefficient by this steer for all the nutrients. This animal consumed 312.4 grams of nitrogen for the five days, and excreted 346.5 grams, making a loss of 213.1 grams of protein, or 10.9 per cent of the nitrogen consumed. There was excreted in the urine 51.76 per cent, while with steer No. 2, on practically the same ration, only 28.16 per cent of the nitrogen was in the urine. The results obtained with steer No. 2 were more satisfactory throughout. He showed a normal digestion coefficient for all the nutrients, but it was hardly enough for the proteids to make a theo- retical maintenance ration for him; yet we find a daily gain in Table 17 of 127.6 grams of this nutrient. There was a quite uniform gain of nitrogen for both steers during the fourth digestion period in which prickly pear and cotton-seed meal composed the ration. The gain for steer No. 1 amounted to 30.46 per cent, and for steer No. 2, 23.07 per cent. 36 DIGESTIBILITY OF PRICKLY PEAR BY CATTLE. Fifteen pounds of alfalfa per day was the ration for both steers during the fifth period. The digestion coefficient for the two was close enough to make a nutritive ratio for both of 1 to 4.75. From Table 15 it may be seen that steer No. 1 digested or retained in his system 1.31 pounds, and No. 2, 1.32 pounds of protein during this period. According to Wolff's standard for oxen at rest in stalls these figures are 0.71 pound for steer No. 1 and 0.65 pound for steer No. 2 in excess of the amount required for maintenance; yet we find that during the five days steer No. 1 gained only 302.5 grams (0.66 pound) of protein, and steer No. 2 actually lost 222.5 grams (0.5 pound). Why there should be such a slight gain of protein for steer No. 1 and a loss for No. 2 when the proteids actual!}' digested by both were far in excess of the estimated amount required we are at a loss to say. It may be explained, however, by the supposition that because of the narrow nutritive ratio of the feed neither steer had a maintenance ration of nonproteids, and to supply the necessary energy their bodies broke down the proteids and used the nonni- trogenous part of the molecule, excreting the nitrogenous portion produced from the cleavage through the kidneys. That such is the case would seem to be shown by the fact that steer No. 2, for exam- ple, in consuming 727.6 grams (1.6 pounds) of nitrogen excreted 509.4 grams (1.1 pounds) or 70.01 per cent in the urine. TABLE 17. Income and outgo of nitrogen during the five digestion periods. Ex- peri- ment No. Feed. Steer No. Nitrogen in urine. Nitrogen in feces. Total nitrogen excreted. Total nitrogen eaten. Nitrogen (gain, +; loss, ). Grams. Grams. Grams. Grams Grama. 1 Prickly bear (Opuntia lindhfimeri) ... { I . 52.5 47.1 86.6 84.4 139.1 131.5 211.6 198.4 + 72.5 + 66.9 2 Pricklv pear. (O. /arris?) I 1 1 2 86.0 121.5 60.1 81.7 146.1 203.2 99.2 140.0 - 46.9 - 63.2 3 Pricklv pear (0. engelmannii rvdoi- f 1 161.7 184.8 :<4t;. .'. 312. 4 - 34.1 dts) and alfalfa 1 2 100.9 155. 3 i r > . 358 4 + 102.1 4 Pricklv pear (O. engelmannii cydoi- f 1 359.3 207.7 66 r.o 815.3 +248.3 dfs\ ami pot ton-seed nim.1. _ \ 2 431.5 242.2 67 ; : 875. 7 + 202.0 5 Alfalfa ! J 430.0 509.4 246.5 253.8 676. 5 763.2 724.9 727.6 + 48.4 - 35.6 Ex- peri, ment No. Feed. Steer No. Proteids (gain, +; loss, ). Nitrogen (gain, +; loss, ) . Excreted nitrogen in feces. Excreted nitrogen in urine. Grams. Per cent. Per cent. Per cent. 1 Prickly pear (Opunlia lindhfimeri) ;{ 1 2 + 453.1 + 418.1 +34.26 +33.72 40.93 42.54 24.82 23.74 2 Prickly pear (O. iarri* ?) i 2 - 293.1 - 395.0 -47.28 -45.14 60.58 58.35 86.69 86.79 3 Pricklv pear (0. engelmannii cydoides) i - 213.1 -10.92 59.15 61.76 and alfalfa. J + 6.' - l 4-28 . J Ml 43 34 28 16 4 Prickly pear (O. engelmannii cydoides) and cotton-seed meal. 1 + 1,551.9 +30.46 + 1,262.5 +23.07 25.47 54.09 49.16 5 Alfalfa | 1 + 302.5 + 6.68 34.00 59.32 " 222.5 4.89 34.88 70.01 SUMMARY OF RESULTS. 37 CONCLUSIONS. (1) The average digestibility of the nutrients of prickly pear as determined in the first experiment where Opuntia lindheimeri was used were: Dry matter, 65.86 per cent; ash, 33.68 per cent; pro- tein, 57.47 per cent; fat, 68.38 per cent; crude fiber, 41.32 per cent; nitrogen-free extract, 81.78 per cent l __ In the second experiment where the variety 0. l&vis? was used the coefficients of digestion were: Dry. matter, 63.96 per cent; ash, 35.81 per cent; protein, 40.87 per cent; fat, 69.02 per cent; crude fiber, 53.99 per cent; nitrogen-free extract, 78.95 per cent. In general these results would perhaps show a somewhat low coefficient for protein, a decidedly low coefficient for ash, but a very high coefficient for the nitrogen-free extract. The total digest- ible nutrients are about equal to those of immature green corn fodder. (2) Our experiments seem to show that when prickly pear is fed with cured fodders or grams the digestibility of both is increased. For this reason prickly pear has a greater food value than is shown by its analysis and digestion coefficients. (3) The nutritive ratio, i. e., the ratio of proteids to carbohy- drates, is very wide for this feed, and in feeding it to all classes of animals, for whatever purpose, much better results should be obtained when it is fed with some substance of a high protein content. (4) While the digestibility of the ash was apparently small, as noted above, yet the large amount of ash contained in these plants caused more ash to be assimilated from a ration equivalent to 15 pounds of dry matter than is ordinarily assimilated from an equal ration of alfalfa, which has a higher coefficient of digestion for its ash. (5) The steers seldom drank water when fed prickly pear alone. In fact, in feeding a ration of 100 pounds of this feed per day the animals obtained from the feed over 8 gallons of water, which is more than was usually drunk by them when fed cured fodders alone. (6) While no digestion experiments were made with any of the cacti other than prickly pear, the digestion coefficients of the latter could probably be safely used for all other members of this family, since their composition and other characteristics are similar. (7) It may be seen that both steers gained proteids during the first experiment, although both ate a smaller quantity of dry matter which contained less proteids than are required according to Wolff's standard ration for oxen of their weight at rest in stalls. In the second experiment both animals lost proteids, but here steer No. 1 ate less than half of what was eaten by steer No. 1 in the first experiment, and steer No. 2 ate over 3 pounds less than steer No. 2 of experiment NO. 1 . 38 DIGESTIBILITY OF PRICKLY PEAR BY CATTLE. (8) Animals scour quite badly when fed prickly pear alone; besides, other feeds are needed to supply the proper amount of proteids; and for these reasons it is better not to feed it alone. A ration for a 1, 000-pound milch cow of 50 pounds of prickly pear, 10 pounds of wheat bran, and 10 pounds of alfalfa would furnish about the correct theoretical amount of nutrients, in which the ratio of proteids to carbohydrates would be 1 to 5.46. O University of California SOUTHERN REGIONAL LIBRARY FACILITY 405 Hilgard Avenue, Los Angeles, CA 90024-1388 Return this material to the library from which it was borrowed. 1MB." I a Uni\, S< 1