CALIFORNIA AGRICULTURAL EXTENSION SERVICE CIRCULAR 19 MAY, 1928 ARTIFICIAL INCUBATION OF EGGS J. E. DOUGHERTY PUBLISHED BY THE COLLEGE OF AGRICULTURE UNIVERSITY OF CALIFORNIA Cooperative Extension work in Agriculture and Home Economics, College of Agriculture, University of California, and the United States Department of Agriculture cooperating. Dis- tributed in furtherance of the Acts of Congress of May 8 and June 30, 1914. B. H. Crocheron, Director, California Agricultural Extension Service. UNIVERSITY OF CALIFORNIA PRINTING OFFICE BERKELEY, CALIFORNIA 1928 Digitized by the Internet Archive in 2011 with funding from University of California, Davis Libraries http://www.archive.org/details/artificialincuba19doug ARTIFICIAL INCUBATION OF EGGS 1 J. E. D0UGHEETY2 At the beginning of the year 1926, there were 262 commercial hatcheries located in thirty-seven different counties of California, each of which had an incubating capacity of more than 1,000 eggs. The total capacity of the larger hatcheries in the state was 7,781,342 eggs at that time and the grand total, including both small and large hatcheries, was estimated to be approximately 8,000,000 eggs, 3 It has been materially increased since that estimate was made. In addition to the chicks produced in commercial hatcheries, a considerable percentage of farmers and poultry keepers hatch eggs from their own flocks, During the past year many farmers have also begun to use incubators for the hatching of their turkey eggs, It has been demonstrated at the University Farm that turkeys can be hatched and reared equally as well artificially as by natural methods, and the time and rate of hatching controlled to better advantage. It is evident that artificial incubation is growing in popularity. As the use of incubators becomes more widespread, there is a larger demand for comprehensive information concerning how to operate them to obtain most effective results. SELECTING EGGS FOR HATCHING The eggs that are to produce the future layers should be carefully selected for (1) size, (2) shape, (3) color, (4) quality of shell. Size, shape and color of the egg are largely inherited, as pointed out by Benjamin (1920). 4 Such inheritance is also evidenced by the fact that the production of large eggs is a breed characteristic of the Minorca, white eggs a breed characteristic of the Leghorn, and brown eggs a breed characteristic of the Plymouth Rock. Weak-shelled eggs break more easily when being turned in the incubators than eggs of good shell quality and may ' ' dry down ' ' too rapidly, due to the shell being more porous. i This circular applies only to natural draft incubators. The forced draft and agitated air types of mammoth incubators are of such recent development that sufficiently extended data on their operation to warrant publication is not yet available. 2 Associate Professor of Poultry Husbandry and Associate Poultry Husband- man in the Experiment Station. 3 Data from: Voorhies, Edwin C. The California poultry industry: a statis- tical study. California Agr. Exp. Sta, Bui. 413:1-172. 1926. ■i The references cited may be found at the end of this circular. 4 CALIFORNIA AGRICULTURAL EXTENSION SERVICE [ClRC. 19 Continued selection of hatching eggs for the most desirable size, shape, and color should result in the development of a strain produc- ing an increased percentage of such eggs from year to year since like tends to produce like with reference to these characters. In the case of tinted eggs laid by white egg breeds, however, Benjamin (1920) and Dougherty and Gossman (1923) observed that the brown tint may gradually fade out as production increases in early spring. The elimination of tinted eggs from those used for hatching after the time when the less strongly tinted eggs have faded sufficiently so that they cannot be readily distinguished from eggs laid by hens that always lay white eggs is, therefore, of little value ; it will not decrease the " taint" of tint in the breeding flock and perfect a strain that is genetically pure for whiteness of egg shell. This can only be done in stock producing tinted eggs by trapnesting the breeding hens to identify and remove the layers of tinted eggs from the flock, and by using males known to be genetically pure with respect to this factor. Trapnesting to identify hens laying tinted eggs should be done after the molting season and before spring production has increased suffici- ently to cause enough fading of any of the tinted eggs laid to make them difficult to distinguish from white eggs. EFFECT OF TEMPERATURE ON EGGS HELD FOR HATCHING That eggs being held for hatching can be subjected to temperatures closely approaching the freezing point has been shown by a number of investigators. Elford (1921) exposed a number of lots of eggs packed in different ways to temperatures ranging from 14° to 26° Fahrenheit, for 15 minutes to 5 hours, and obtained results indicating that strong-germed eggs will stand more cold than it has been con- sidered safe to expose them to. Mauro (1923) found that eggs kept in a refrigerator at 32.9° F for 24 hours were not appreciably affected. But when held at this temperature for 48 hours the capacity of the embryos to develop was considerably reduced, and after 72 hours of such refrigeration, it was entirely destroyed. Mussehl and Bancroft (1924) found that exposure of hatching eggs to a temperature of 32° F for 6 to 18 hours did not lower their hatching power or result in an unusual number of crippled or otherwise abnormal chicks. Dougherty (1926) found that exposure of eggs held for hatching to temperatures of 28° to 32° F for four successive nightly periods (putting them in the ice box at 5 p.m. and removing them to a room temperature of 60° F at 7 a.m.), plus a continuous period of 38 hours did not result in any significant reduction in the per cent of chicks 1928 ARTIFICIAL INCUBATION OF EGGS hatched. He states that a sufficiently long exposure to a temperature of 32° F would probably have a detrimental effect on hatchability but the brief periods of low temperature to which eggs may be exposed in the poultry districts of California are evidently not cold enough or of sufficient duration to cause any serious injury to hatching eggs. The maximum temperature at which to hold eggs being saved for hatching is generally conceded to be below 70° F. Edwards (1902) found that the lowest temperature at which development can occur lies between 68° and 69.8° F. Gowell (1902) held one lot of eggs at 70° and another lot at 50° F for 10 days and those held at 70° hatched slightly better than the other lot. In this case, however, the hatches were poor and the data meager, so that the results cannot be given much weight. Philips (1909) held three lots of eggs for 14 days at 50°, 65°, and 80° F respectively before hatching. The corresponding hatching results obtained were 70.4, 43.1, and per cent. Just why the lot held at 65° hatched so poorly is not clear. Under the con- ditions existing in California there is apparently more danger of getting hatching eggs too warm than of getting them too cold. A temperature range of 40° to 60° F would appear to be well within the limits of safety. EFFECT OF AGE AND METHOD OF HANDLING ON EGGS FOR HATCHING In table 1 is given the results of the first of a series of trials being made at this Station to determine the effect of age and of method of holding on eggs being saved for hatching. These eggs were held on TABLE 1 Effect of Age and of Daily Turning on Eggs Being Held for Incubation Treatment Age of eggs days Per cent fertile eggs hatched Eggs held on sides in open rack and not turned < 6 10 14 6 10 14 6 10 14 6 10 14 70.0 69.6 60.0 76.2 82 6 Eggs held on sides in covered egg case and not turned - 74.4 57.8 66.0 54.8 79.6 73 4 1 72.0 6 CALIFORNIA AGRICULTURAL EXTENSION SERVICE [ClRG. 19 their sides in a cool cellar and set April 1. The data obtained do not indicate that the age of the eggs up to 10 days or the use of open racks as compared with covered egg cases have any significantly detrimental effect on hatching quality. But whether eggs are turned or not while being held for hatching is evidently important, for the average hatch of chicks to fertile eggs set was 63 per cent in the case of the two groups of eggs that were not turned and 76.4 per cent for the two groups that were turned. An egg case is a convenient receptacle in which to save and turn hatching eggs. If the eggs are held on end with the small ends down, they can be readily turned by elevating one end of the case eight or more inches one day and the opposite end the next. If held on their sides, the full number of fillers would have to be in the case and the cover fastened on before turning. In turning the case would be laid on one side the first day, on one end the second day, on the other side the third day, etc. Revolving the case in this way from day to day would give the eggs a full quarter turn and hold them in their natural position. What brief data there is available, however, as well as the opinion of a large number of experienced hatcherymen, indicate that whether eggs are held on their sides or stood on the small ends is of little consequence for the first week, if turned daily. But if held much longer than one week it is, perhaps, better to keep them on their sides throughout the holding period. Holding the eggs too long may also reduce hatching quality. The average hatch of chicks to fertile eggs (table 1) was 70.9 per cent for the four lots of eggs held 6 days; 72.9 per cent for those held 10 days; and 65.3 per cent for those held 14 days. Waite (1919) found that there w r as a progressive decrease in hatchability as the age of hatching eggs increased beyond one week. Dareste (1883) reported that the longer eggs were held before setting the greater was the per cent of abnormal embryos. The sooner eggs were set after being laid the better. THE INCUBATOR ROOM A well ventilated room where the temperature remains at approxi- mately 60° F is the most desirable environment for an incubator. A basement or semi-basement will usually come nearer to providing desirable temperature conditions than a room above ground because of being better protected from outside weather conditions, If built above ground, well insulated walls and a double roof may be required. !9 28 ] ARTIFICIAL INCUBATION OF EGGS 7 A concrete floor is preferable to a dirt or board floor only because it is easily kept clean and sanitary and is very durable. There is also less objection to wetting down a concrete floor when it is desired to increase the humidity of the incubator room in this way when eggs are hatching. Good ventilation as well as satisfactory lighting of an incubator room can be obtained by the proper installation of windows and exhaust ventilators, Transom or cellar sash should be placed near the ceiling (a ceiling not less than 8 feet high for single deck machines and 9 feet for multi-deck machines is recommended) on one or more sides of the room for the intake of fresh air. One or more exhaust ventilators at least 8 inches in diameter should be located on the wall opposite the windows, or down the center of the room if windows are on both sides. The windows should be well above ground level and spaced approximately 6 feet apart. They should be hinged at the bottom to swing in, and have triangular side shields attached to the window frames. These side shields force all incoming fresh air over the top of each window when open, and help to prevent drafts, A light-weight, removable, burlap covered frame made to rest on top of the wooden side shields and to fully cover each window opening when the windows are open can be provided, if necessary, for use on windy days, It will reduce the velocity of the incoming fresh air and prevent the setting up of strong enough air currents in the incubator room to affect the incubator lamps, if lamps are used, or the tempera- tures of any of the machines. One exhaust ventilator should be sufficient for approximately 300 square feet of floor space. It should be built with the bottom about 18 inches above the floor and the top extending well above the highest point of the roof ; the higher the top of this ventilator and the more efficient the ventilator cap, the stronger will be the suction (revolving metal caps have been found more effective than stationary caps). This ventilator should be provided with a conveniently located damper to regulate the amount of air passing through it so as not to exhaust the air from the room too rapidly. A trap door in the ventilator near the ceiling, as well as one or more large ceiling ventilators, may also prove of value in removing hot air from the incubator room in very warm weather and preventing the temperature from rising unduly. CALIFORNIA AGRICULTURAL EXTENSION SERVICE [ClRC. 19 GETTING THE INCUBATOR READY Before the opening of the hatching season each year, the incubators should be inspected to see that they are in good working order. If any of the incubators have the ether wafer type of thermostat, an extra wafer should be kept on hand in case one of those in use should become corroded and allow the vaporized ether to escape. The incubator should be leveled with a spirit level. If the egg trays in natural draft machines are not all on the same level, the eggs that are high will be subjected to a higher temperature than those that are lower. The even distribution of heat to all parts of the egg chamber can be checked by first operating the incubator without eggs but with a number of thermometers located at different places on the egg trays and having the thermometer bulbs l 1 /^ inches above the bottoms of the trays. If the temperature readings show a distinctly uneven dis- tribution of heat, the cause should be looked for, and corrected if possible, before the incubator is set. If temperature variations in different parts of the egg chamber do not exceed 1% degrees any harm to the eggs that might accrue from this amount of unevenness may be largely neutralized by the method of manipulating the eggs. For example, the position of the trays can be changed one or more times daily ; the trays can be turned end for end ; the position of the eggs on the trays can be changed ; or a combination of such manipulations can be used, depending on the style of incubator. Testing Electric Incubators. — Electric incubators should be heated to operating temperature to be certain that there are no breaks or short circuits in the wiring and that the thermostatic regulator is working smoothly. The breaker contact points should be lightly filed with a fine magneto file to clean them and make the contact surfaces perfectly flat and parallel to each other. A full contact of the points is necessary to reduce arcing to a minimum. Oil and Gas Heated Incubators. — The lamp of each lamp heated machine should be thoroughly cleaned before using, each season, the burner boiled in a solution of washing soda, and a new wick put in, if necessary. If gas burners are used they should be examined to see that they are in good working order. In beginning the hatch a medium flame is best, for if too small a flame be used to start with it cannot be turned low enough at the L928 ARTIFICIAL INCUBATION OF EGGS end of the hatch in warm weather to keep the temperature from running up. If too high a flame is used the lamp will smoke. Lamps should be trimmed and filled each day after turning the eggs. If filled before turning, the hands may become oily enough to leave oil on the eggs when turning them and perhaps injure the embryos. The wick can be most easily trimmed by covering the end of the finger with a piece of cloth and rubbing off the charred crust. After turning the wick just high enough to expose the charred part above the wick tube, the top of the wick should be wiped off in one direction only ; this lays all the threads of the wick in the same direc- tion and results in a better shaped flame. After wiping, the wick is turned up a bit and the corners patted down to do away with a high cornered flame that would smoke. The flame should be straight across the top and have rounded corners. Disinfection, — Before every hatch the incubator and trays should be thoroughly cleansed and disinfected. If convenient the movable parts should be placed in the sun to dry and air as direct sunshine is' a most effective germicide. Disinfection of the incubator is most easily done, perhaps, with a suitable spray pump using about a 2 per cent solution of some good preparation such as formalin, a sodium hypochlorite disinfectant, a cresol compound, or any of the phenol disinfectants. In the case of the phenol disinfectants (commonly known as coal tar sprays or sheep dips) care should be taken to use, for the incubators, only carefully manufactured preparations that are thoroughly emulsified and do not leave an oily or sticky residue. Germicides may vary greatly in strength as shown by their carbolic or phenol coefficients. The phenol coefficient of a disinfectant is an indication of its germicidal value as compared with pure carbolic acid. In order that the purchaser may more fully determine the worth of proprietary phenol disinfectants, the phenol coefficient should appear on the label. For example, a disinfectant having a phenol coefficient of 5 has been found by test to act five times more rapidly in destroying typhoid bacteria in pure culture than pure carbolic acid or phenol. Thermometer. — The incubator thermometer should be tested for accuracy every season by comparing it with a clinical or fever ther- mometer. This is best done by placing both thermometers in hike warmwater at approximately 103° F. With bulbs close together and while stirring the water, the thermometer readings should be taken. The difference in reading, if any, between clinical and incubator thermometer will represent the amount in degrees that the incubator 10 CALIFORNIA AGRICULTURAL EXTENSION SERVICE [ClRC. 19 thermometer is inaccurate. It is the better plan to destroy inaccurate thermometers and use only accurate ones. Setting the Eggs. — The incubator should be accurately regulated to provide proper temperature, ventilation, and moisture conditions before the eggs are set. It is just as important that embryonic development be started under the most favorable environmental conditions as it is that it be continued and concluded under such conditions. Failure to utilize the utmost care from the very beginning in regulating the incubator, and in handling the eggs to prevent unnecessary jarring, may contribute materially to the "in-shell" mortality during the hatching period. OPERATING THE INCUBATOR Temperature. — Experimental work (1915) at this station has shown that the temperature throughout the hatch in incubators with natural air circulation should be 102 degrees when the center of the thermometer bulb is on a level with the tops of the eggs. Whether it touches a fertile egg or not is unimportant. If the thermometer is hung so that the center of the bulb is above or below the tops of the eggs, the temperature must be run higher or lower than 102 degrees as indicated in figure 1. Similar results were obtained by Philips (1923). The heat in this type of incubator usually comes into the egg chamber from the top so that the nearer the thermometer is to the top of the egg chamber the higher it will read. It is, perhaps, most convenient, however, to maintain the same thermometer reading from day to day throughout the incubation period and not have to remember to lower or raise this reading from time to time. This can be done if the position of the thermometer is such that the center of the bulb is level with the tops of the eggs. Ventilation. — Good ventilation is a very important factor in the process of incubation. During growth, the embryo is nourished by the supply of stored-up food in the egg. In order to utilize this food and transform it into new body tissue, into heat, or into muscular action such as the pumping of the blood through the blood vessels, oxygen is necessary. The network of blood vessels which extends close to the inside of the shell and to the air cell, takes up oxygen from the fresh air that enters through the pores of the shell and throws off carbon dioxide, which passes out through the shell. Briefly stated, the developing embryo breathes in fresh air and gives off carbon dioxide through the pores of the shell. 1928 ARTIFICIAL INCUBATION OF EGGS 11 The air cell plays an important part in this respiratory process as evidenced by the fact that stopping up the pores of the shell over the air cell will more seriously injure the embryo than will stopping the pores of any other part of the shell. As the embryo grows the air cell enlarges due to loss of water and shrinking of the shell content ; and in so doing, an increasingly larger air space is provided from day to day into which carbon dioxide and water vapor can be discharged and from which oxygen can be taken up. This continued increase in size of the air cell of a normally developing egg from /06 k % IT) too Ho.l Thermometer with center of bu/b ■i", a bo re tops of* egos. /Vo.£ Thermometer w/th center ^ of bu/b /eye/ w//b tops of eggs, y Ho.3 TKZZO^^ bulb level *"*> cenTero f FIRST WEEK 3ECOHD WEEK Tti/RO WEEK Fig. 1. — The trend of temperature readings from week to week during incubation. Thermometer No. 1, suspended with center of bulb % inch above the eggs, registers higher at first than thermometer No. 2, which is on a level with the tops of the eggs, because it is closer to the source of the heat in the top of the egg chamber. Thermometer No. 3, with center of bulb level with center of eggs, registers lower than No. 2 as it is further away from the top of the egg chamber. As the embryos grow, however, and the heat given off by the eggs increases, less artificial heat is required. Since thermometer No. 1 is y>2 inch above the eggs and affected more by the artificial heat from the top of the egg chamber than by the natural heat from the eggs, it will read lower from day to day as the artificial heat is reduced, whereas thermometer No. 3, which is further from the top of the egg chamber and down between the eggs, will read higher and higher, due to the increasing heat from the eggs as the embryos grow. the first to the twentieth day of incubation, paralleling, as it does, the growth of the embryo and its ventilation requirements, may be looked upon as indicative of the continual increase in its oxygen require- ments. As explained further under the section on moisture, it serves as a guide to the incubator operator in indicating whether or not the rate of flow of fresh air through the egg chamber and the humidity of this air are meeting the needs of the developing eggs. Hannas (1920) measured the air cells of several thousand eggs in an effort to determine the proper size of air cell at different stages of incuba- tion. He reports the depth of the air cell to be 2 % 2 of an inch on the 12 CALIFORNIA AGRICULTURAL EXTENSION SERVICE [ClRC. 19 8th day, between 2 *% 2 an d ] % 6 of an inch on the 14th day, and between 15 / 1Q and 3 % 2 of an inch on the 19th day. He states that these measurements were found to be approximately equivalent to an air cell a little less than one-third the size of the egg on the 8th day, one-third the size of the egg on the 14th day, and two-fifths the size of the egg on the 19th day. The ventilation of the incubator should be such as to carry fresh air into the egg chamber as rapidly as needed and to carry carbon dioxide away as rapidly as it is given off by the eggs. Insufficient ventilation will seriously injure the developing embryos by depriving them of enough oxygen and causing the carbon dioxide content of the air surrounding the eggs to increase. Lamson and Edmond (1914) found that if the carbon dioxide content of the air about the eggs increased beyond 150 parts in 10,000 there was a high mortality of the embryos, which rose still higher when it exceeded 200 parts in 10,000. Too much ventilation, at least after the first week, probably cannot be given, provided proper temperature and moisture con- ditions are maintained in the egg chamber. Hatching eggs require very little ventilation the first day or two of incubation. Therefore, in incubators equipped with adjustable ventilators, these can be almost closed the first two days and then opened more and more as the incubation period advances, using the gradual increase in the size of the air cell or the loss in weight of the eggs, or both, to guide one in determining their proper adjustment. This is discussed in detail in the section on moisture. A properly designed incubator should permit of sufficient control of ventilation to meet changing weather conditions as well as the changing requirements of the developing embryo within the egg. Since the difference in temperature between the air of the egg chamber and the air of the room is one of the factors affecting the rate of flow of air through an incubator, the intake and exhaust ventilators need be opened less at the beginning of the incubation period in a cool room than in a warm room. They should then be opened a little more every few days, as the embryos develop, until there is enough air passing through the egg chamber when the hatch is completed so that the chicks do not pant from a lack of fresh air. The incubator manufacturer whose instructions are to open the ventilators after the first week and nearly close them again on the nineteenth day is tacitly admitting that his machine is either over- ventilated with the ventilators wide open or defective in moisture supply. If over-ventilated, fuel is being wasted from a too rapid 1928] ARTIFICIAL INCUBATION OF EGGS 13 circulation of air through the egg chamber (a very important matter with an electric incubator operating on a house lighting rate). If adequately ventilated with the ventilators wide open on the eighteenth day, they should not be closed on the nineteenth day. The ventila- tion requirements of the chicks at this time are increasing and not diminishing. Restricting ventilation to cause the humidity of the egg chamber to increase while the chicks are hatching should not be necessary if the moisture device in the incubator is functioning properly in regulating the humidity of the egg chamber. Moisture. — The process of breathing in the developing egg is closely analogous to that in human beings. The exhaled air is laden with moisture, and it is as a result of giving off moisture in this way that the eggs "dry down" during embryonic growth. In this drying down process there is a gradual loss of the w 7 ater content of the egg and, as previously indicated, a correspondingly gradual increase in the size of the air-cell. When the air passing through the egg chamber is very dry, however, it not only takes up and carries off the moisture naturally exhaled by the egg, but may pass through the porous shell and absorb still more moisture. Such excessive drying down is detrimental. It is, therefore, necessary to have the air passing through the egg chamber sufficiently charged with moisture to prevent any undue evaporation of water from the egg. Ventilation and moisture conditions are closely related and cannot be considered separate problems. Geographical location, time of year, and other factors must determine whether artificial means of adding moisture to the air entering the egg chamber are necessary or not. In the better types of incubators, ventilation is very well taken care of, so that the chief problem to consider is the maintenance of sufficient moisture in the circulating air. One should always follow the instructions sent out by the incubator manufacturer in this regard until sufficient experience has been gained to enable one to act intelligently in making any change that may appear advisable. During the period of incubation frequent observation of the air- cells will indicate the rate of evaporation of the egg and will help one to determine if too much or too little moisture is being supplied. Experience will soon teach one the normal rate of evaporation as shown by a gradual increase in the size of the air-cell. It is a good plan, however, for the beginner to set a hen on the ground in an out-door, bottomless setting coop where the earth is reasonably moist and well shaded at the same time that he sets the incubator and to compare the increase in the size of the air-cell in both cases every few days. 14 CALIFORNIA AGRICULTURAL EXTENSION SERVICE [ClRC. 19 Yet another method of checking the rate of evaporation of water from the eggs is to weigh them, as was done by Atwood (1917). He weighed each tray when set and again at the same time each day during the period of incubation. From these weighings he worked out the following tabulation indicating the normal loss in weight of one hundred eggs day by day for the first nineteen days, Day Ounces Day Ounces Day Ounces 1 1.65 8 13.44 15 25.66 2 3.31 9 15.16 16 27.44 3 4.96 10 16.88 17 29.21 4 6 62 11 18.60 18 30.99 5 8.28 12 20.33 19 32.77 6 10.00 13 22.10 7 11.72 14 23.88 In the practical use of Atwood 's data, weighing the eggs when set and again on the 4th, 7th, 11th, 15th, and 19th days should be sufficient. After the chicks have begun to hatch, optimum humidity of the egg chamber is indicated by a light film of moisture or a few beads of water appearing along the lower inside edge of the glass of the incubator door, whereas a considerable accumulation of moisture on the glass door would indicate too much humidity. This latter con- dition can be corrected by increasing the ventilation or by reducing the amount of moisture supplied to the air of the egg chamber. Tco little humidity at hatching time is indicated by the absence of moisture from the inside of the glass door, and by the rapid drying and whitening of the shell membranes exposed around the edges of the opening where the chick has pipped the shell and before it has gotten out. As the shell membranes dry they become tough and difficult for the chick to tear through. The watery albumen coating the inside of the inner shell membrane also becomes more and more viscid with loss of moisture, and serves to glue the membranes to the chick and retard its efforts to escape from the shell. The membranes should remain moist while the chick is breaking out of the shell, for they are then soft and easily torn and do not adhere to the chick's body. The humidity of the eg£- chamber can be increased by means of wet sponges or cloths, by sprinkling the eggs, by inserting shallow pans, etc. The sponges, cloths, and pans can be suspended above the eggs or placed below them. Saturated sand can be placed in the pans in lieu of water and will aid in hastening evaporation as the moist particles of sand present a larger evaporating surface than does a level water surface. These, however, are more or less make- 1928] ARTIFICIAL INCUBATION OF EGGS 15 shift methods of providing moisture and cannot be compared with a well designed, built-in system of humidity control. Turning the Eggs. — Turning is usually begun forty-eight hours after the eggs are put into the incubator, and continued daily until the first egg pips, Hannas (1920), however, obtained best results when turning was begun on the first day. Turning should be done at least twice and preferably three or four times a day, if automatic turning trays are used. The results obtained to date at the California Agricultural Experi- ment Station indicate that frequent turning of the eggs each day is beneficial. Payne (1921) also observed favorable results from fre- quent daily turning. The eggs do not have to be turned completely over. All that is necessary is to move them around so that each egg is turned more or less. Cooling. — Cooling is intended to air the eggs and it is said to strengthen the embryos. It corresponds, perhaps, to the opening of all of the windows by the housewife each morning to air the bedroom. Data is steadily accumulating, however, to indicate that cooling is of no real value to the eggs hatched in a well ventilated incubator; in a deficiently ventilated incubator it is undoubtedly of material aid to the hatching process in overcoming inadequate ventilation of the egg chamber. When eggs are cooled the trays should be placed on the top of the incubator or on a table. No part of the tray should project beyond the table or incubator top or the eggs will cool unevenly. The incubator door should not be left open for the aim is to cool the eggs, not the incubator. The hen's body temperature is the same when she returns to the eggs as it was when she left them. Cooling is usually begun on the seventh day, and the eggs cooled once a day thereafter till the first egg pips. The proper length of time to cool, each day, is generally determined by the eye test, In this test the small ends of a few eggs are held to the eye and when they feel barely warm it is considered that sufficient cooling has been given. During the early part of the incubating period the eggs will cool down more or less rapidly, depending on the temperature of the room, but as the embryos grow, cooling will take place more slowly, other things being equal. Testing. — The eggs are usually tested the first time between the fourth and eighth day of incubation and again between the fourteenth and eighteenth days. The purpose of the first test is to remove all infertile eggs and the dead-germ eggs up to that time. In this first 16 CALIFORNIA AGRICULTURAL EXTENSION SERVICE [Circ. 19 test the dead-germ eggs will generally appear addled or show blood clots or blood rings. Every egg in which a dark, movable spot, with numerous radiating blood vessels, is not distinctly visible at this time should be discarded. Only strong-germed eggs will hatch vigorous chicks. On the fourteenth day the eggs containing living embryos will be largely opaque, with a reddish cast to the lighter areas and with large blood vessels. Dead germs will show less development and no large blood vessels, and the lighter areas will have a pale yellow appearance. These dead-germ eggs as well as the infertile eggs, can be hard boiled with the shells on (held at boiling temperature for at least 30 Dead germ, seventh day. Fertile egg, seventh day. Fig. 2 (From Circular 233) Infertile egg. minutes), ground fine in a meat grinder, and fed to growing chicks, mixed into the dry mash two or there times a week at the rate of one egg to twenty-five or more chicks. The Hatch. — After the first egg pips, the incubator should not be opened again until the hatch is over. When the hatch is completed, as evidenced by the presence of no more wet chicks on the egg trays, the trays can be removed. If the chicks in the nursery trays pant, the incubator doors should be wedged open enough to stop the panting without cooling the egg chamber sufficiently to cause a thermometer on the egg tray to fall below 100° F. After wedging open the doors the flame (if using an oil or gas heated incubator) may have to be turned up to keep the chicks comfortable. The egg chamber should be kept dark to keep the chicks quiet. This can be done by fastening paper or dark cloth over the incubator doors. Twenty-four hours after the hatch is completed the chicks can be removed to the brooder. Many poultrymen like to put them in warmed day old chick boxes when the egg trays are removed instead of holding them in the nursery till they are taken to the brooder. 1928 ] ARTIFICIAL INCUBATION OF EGGS 17 TURKEY AND OTHER EGGS The available evidence to date would indicate that turkey and duck eggs and the eggs of other domestic fowl should receive the same treatment as hen eggs when incubated artificially. These eggs would seem to have the same requirements as regards temperature, ventila- tion, turning, cooling, and moisture as the eggs of the hen. BIBLIOGRAPHY Atwood, H. 1917. The incubation of hen eggs. West Virginia Agr. Exp. Sta. Circ. 25: 1-24. Benjamin, E. W. 1920. A study of selections for the size, shape, and color of hen's egg. Cornell Agr. Exp. Sta, Memoir 31:195-312. Dareste, C. 1883. Nouvelles recherches sur la production des monstres, dan 1 'oeuf de la poule, par l'effet de 1 'incubation tardive. Comp. Rend. 96: 444-446. Dougherty, J. E. 1915. Incubator temperatures. California Agr. Exp. Sta. Ann. Ept. 1914- 15:37-38. 1926. Studies in incubation. The effect of low temperatures previous to incubation on hatchability of eggs set. Am. Jour. Physiol. 79: 39-43. Dougherty, J.E., and S. S. Gossman. 1923. Observations on tint in white eggs. California Agr. Exp. Sta. Ann. Ept. 1922-23:221-222. Edwards, C. L. 1902. The physiological zero and the index of the egg of the domestic fowl, Gallus domesticus. Am. Jour. Physiol. 6:351-397. Elford, F. C. 1921. Dominion of Canada, Dept. Agr., Interim Rpt. Poultry Husbandman for year ending March, 1921:3-29. Gowell, G. M. 1902. Experiments in incubation. Maine Agr. Exp. Sta. Eighteenth Ann. Kept. : 18-25. II ANN AS, E. E. 1020. Embryo mortality. Jour. Am. Assn. Inst. Invest. Poultry Husbandry 6:77-79. Lamson, G. H., and H. D. Edmond. 1914. Carbon dioxide in incubation. Storrs Agr. Exp. Sta. Bui. 76:219-258. 18 CALIFORNIA AGRICULTURAL EXTENSION SERVICE [ClRC. 19 Mauro, F. 1923. II trattamento frigarifieo della nova (di gallina) e la sur influenza sulla capacita di sviluppos della macula germinativa. Atti della Soc. Ital. de Seienz 62:239. (Abstr. in Institute Internat. Du Froid. Monthly Bui. Information on Refrigeration. English ed. 5:5-508.) Mussehl, E. F., and P. Bancroft. 1924. Effect of low temperatures on hatching power of hen's eggs. Poultry Sci. 4:79. Payne, L. F. 1921. A study of multiple turning of incubated eggs. Jour. Am. Assn. Instruct. Invest. Poultry Husbandry 7:17-20. Philips, A. G. 1909. Keeping eggs for hatching. Kansas Farmer 47:3-7. Waite, R, H. 1919. The effect of age of eggs on their hatching quality. Maryland Agr. Exp. Sta. Bui. 233:87-101. STATION PUBLICATIONS AVAILABLE FOR FREE DISTRIBUTION BULLETINS No. No. 253. Irrigation and Soil Conditions in the 3 86. Sierra Nevada Foothills, California. 262. Citrus Diseases of Florida and Cuba 3 87. Compared with those of California. 388. 263. Size Grades for Ripe Olives. 268. Growing and Grafting Olive Seedlings 389. 273. Preliminary Report on Kearney Vine- 390. yard Experimental Drain, Fresno County, Calif. 391. 277. Sudan Grass. 278. Grain Sorghums. 392. 279. Irrigation of Rice in California. 393. 283. The Olive Insects of California. 394. 304. A Study of the Effects of Freezes on Citrus in California. 310. Plum Pollination. 395. 313. Pruning Young Deciduous Fruit Trees. 396. 324. Storage of Perishable Fruits at Freez- ing Temperatures. 397. 328. Prune Growing in California. 331. Phylloxera-resistant Stocks. 398. 335. Cocoanut Meal as a Feed for Dairy 400. Cows and Other Livestock. 402. 340. Control of the Pocket Gopher in 404. California. 405. 343. Cheese Pests and Their Control. 406. 344. Cold Storage as an Aid to the Mar- 407. keting of Plums, a Progress Report. 347. The Control of Red Spiders in Decid- uous Orchards. 408. 348. Pruning Young Olive Trees. 409. 349. A Study of Sidedraft and Tractor Hitches. 350. Agriculture in Cut-Over Redwood Lands. 410. 353. Bovine Infectious Abortion, and As- sociated Diseases of Cattle and New- born Calves. 411. 354. Results of Rice Experiments in 1922. 357. A Self-Mixing Dusting Machine for 412. Applying Dry Insecticides and Fun- gicides. 358. Black Measles, Water Berries, and 414. Related Vine Troubles. 361. Preliminary Yield Tables for Second- 415. Growth Redwood. 416. 362. Dust and the Tractor Engine. 363. The Pruning of Citrus Trees in Cali- 417. fornia. 364. Fungicidal Dusts for the Control of 418 Bunt. 366. Turkish Tobacco Culture, Curing, 419. and Marketing. 367. Methods of Harvesting and Irrigation 420. in Relation to Moldy Walnuts. 368. Bacterial Decomposition of Olives 421. During Pickling. 422! 369. Comparison of Woods for Butter Boxes. 423. 370. Factors Influencing the Development of Internal Browning of the Yellow 424. Newton Apple. 371. The Relative Cost of Yarding Small 425. and Large Timber. 426 373. Pear Pollination. 374. A Survey of Orchard Practices in 427. the Citrus Industry of Southern California. 428. 375. Results of Rice Experiments at Cor- tena, 1923, and Progress in Experi- ments in Water Grass Control at the 429 Biggs Rice Field Station, 1922-23. 430' 377. The Cold Storage of Pears. 431 3 79. Walnut Culture in California. 380. Growth of Eucalyptus in California 432. Plantations. 382. Pumping for Draininge in the San 433. Joaquin Valley, California. 385. Pollination of the Sweet Cherry. Bearing Deciduous Fruit Cali with Quality of it is Har- Soil Fumi- Pruninj Trees. Fig Smut. The Principles and Practice of Sun- Drying Fruit. Berseem or Egyptian Clover. Harvesting and Packing Grapes in California. Machines for Coating Seed Wheat with Copper Carbonate Dust. Fruit Juice Concentrates. Crop Sequences at Davis. I. Cereal Hay Production in fornia. II. Feeding Trials Cereal Hays. Bark Diseases of Citrus Trees in Cali- fornia. The Mat Bean, Phaseolus Aconitifo- lius. Manufacture of Roquefort Type Cheese from Goat's Milk. Orchard Heating in California. The Utilization of Surplus Plums. The Codling Moth in Walnuts. The Dehydration of Prunes. Citrus Culture in Central California. Stationary Spray Plants in California. Yield, Stand, and Volume Tables for White Fir in the California Pine Region. Alternaria Rot of Lemons. The Digestibility of Certain Fruit By- products as Determined for Rumi- nants. Part I. Dried Orange Pulp and Raisin Pulp. Factors Influencing the Fresh Asparagus after vested. Paradichlorobenzene as a gant. A Study of the Relative Value of Cer- tain Root Crops and Salmon Oil as Sources of Vitamin A for Poultry. Planting and Thinning Distances for Deciduous Fruit Trees. The Tractor on California Farms. Culture of the Oriental Persimmon in California. Poultry Feeding : Principles and Prac- tice. A Study of Various Rations for Fin- ishing Range Calves as Baby Beeves. Economic Aspects of the Cantaloupe Industry. Rice and Rice By-Products as Feeds for Fattening Swine. Beef Cattle Feeding Trials, 1921-24. Cost of Producing Almonds in Cali- fornia : a Progress Report. Apricots (Series on California Crops and Prices). The Relation of Rate of Maturity to Egg Production. Apple Growing in California. Apple Pollination Studies in Cali- fornia. The Value of Orange Pulp for Milk Production. The Relation of Maturity of fornia Plums to Shipping Dessert Quality. Economic Status of the Grape Industry. Range Grasses of California. Raisin By-Products and Bean Screen- ings as Feeds for Fattening Lambs. Some Economic Problems Involved in the Pooling of Fruit. Power Requirements of Electrically Driven Manufacturing Equipment. Cali- and No. 434. 435. 436. 437. 438. 439. No. 87. 115. 117. 127. 129. 136. 144. 157. 164. 166. 173. 178. 179. 202. 203. 209. 212. 215. 217. 230. 231. 232. 234. 238. 239. 240. 241. 243. 244. 245. 248. 249. 250. 252. 253. 254, 255. BULLETINS- Investigations on the Use of Fruits in Ice Cream and Ices. The Problem of Securing Closer Relationship Between Agricultural Development and Irrigation Con- struction. I. The Kadota Fig. II. Kadota Fig Products. Economic Aspects of the Dairy In- dustry. Grafting Affinities with Special Refer- ence to Plums. The Digestibility of Certain Fruit By- products as Determined for Rumi- nants. Part II. Dried Pineapple Pulp, Dried Lemon Pulp, and Dried Olive Pulp. (Continued) No. 440. The Feeding Value of Raisins and Dairy By-Products for Growing and Fattening Swine. 441. The Electric Brooder. 442. Laboratory Tests of Orchard Heaters. 443. Standardization and Improvement of California Butter. 444. Series on California Crops and Prices : Beans. 445. Economic Aspects of the Apple In- dustry. CIRCULARS No. Alfalfa. Grafting Vinifera Vineyards. The selection and Cost of a Small Pumping Plant. House Fumigation. The control of Citrus Insects. Melilotus Indica as a Green-Manure Crop for California. Oidium or Powdery Mildew of the Vine. Control of Pear Scab. Small Fruit Culture in California. The County Farm Bureau. The Construction of the Wood-Hoop Silo. The Packing of Apples in California. Factors of Importance in Producing Milk of Low Bacterial Count. County Organization for Rural Fire Control. Peat as a Manure Substitute. The Function of the Farm Bureau. Salvaging Rain-Damaged Prunes. Feeding Dairy Cows in California. Methods for Marketing Vegetables in California. Testing Milk, Cream, and Skim Milk for Butterfat. The Home Vineyard. Harvesting and Handling California Cherries for Eastern ' Shipment. Winter Injury to Young Walnut Trees During 1921-1922. The Apricot in California. Harvesting and Handling Apricots and Plums for Eastern Shipment. Harvesting and Handling California Pears for Eastern Shipment. Harvesting and Handling California Peaches for Eastern Shipment. Marmalade Juice and Jelly Juice from Citrus Fruits. Central Wire Bracing for Fruit Trees. Vine Pruning Systems. Some Common Errors in Vine Prun- ing and Their Remedies. Replacing Missing Vines. Measurement of Irrigation Water on the Farm. Support for Vines. Vineyard Plans. The Use of Artificial Light to In- crease Winter Egg Production. Leguminous Plants as Organic Fer- tilizers in California Agriculture. 257. 258. 259. 261. 264. 265. 266. 267. 269. 270. 273. 276. 277. 278. 279. 281. 282. 283. 284. 286. 287. 288. 289. 290. 292. 293. 294. 296. 298. 300. 301. 302. 304. 305. 306. 307. 308. 309. 310. 311. The Small-Seeded Horse Bean (Vicia faba var. minor). Thinning Deciduous Fruits. Pear By-Products. Sewing Grain Sacks. Preliminary Essentials to Bovine Tu- berculosis Control in California. Plant Disease and Pest Control. Analyzing the Citrus Orchard by Means of Simple Tree Records. The Tendency of Tractors to Rise in Front; Causes and Remedies. An Orchard Brush Burner. A Farm Septic Tank. Saving the Gophered Citrus Tree. Home Canning. Head, Cane and Cordon Pruning of Vines. Olive Pickling in Mediterranean Countries. The Preparation and Refining of Olive Oil in Southern Europe. The Results of a Survey to Deter- mine the Cost of Producing Beef in California. Prevention of Insect Attack on Stored Grain. Fertilizing Citrus Trees in California. The Almond in California. Milk Houses for California Dairies. Potato Production in California. Phylloxera Resistant Vineyards. Oak Fungus in Orchard Trees. The Tangier Pea. Alkali Soils. The Basis of Grape Standardization. Propagation of Deciduous Fruits. Control of the California Ground Squirrel. Possibilities and Limitations of Coop- erative Marketing. Coccidiosis of Chickens. Buckeye Poisoning of the Honey Bee. The Sugar Beet in California. Drainage on the Farm. Liming the Soil. A General Purpose Soil Auger and Its Use on the Farm. American Foulbrood and Its Control. Cantaloupe Production in California. Fruit Tree and Orchard Judging. The Operation of the Bacteriological Laboratory for Dairy Plants. The Improvement of Quality in Figs. The publications listed above may be had by addressing College of Agriculture, University of California, Berkeley, California. 15m-5,'28