UNIVERSITY OF CALIFORNIA COLLEGE OF AGRICULTURE AGRICULTURAL EXPERIMENT STATION BERKELEY, CALIFORNIA CIRCULAR 325 May, 1932 CONSTRUCTION AND OPERATION OF ELECTRIC BROODERS 1 J. E. DOUGHERTY? and B. D. M0SES3 Electric brooder in operation INTRODUCTION Electricity is a very desirable source of heat for the artificial brooding of poultry because of its convenience and low fire hazard. It is convenient because it obviates the filling of lamps, trimming of wicks, tending coal heaters, etc., and provides accurate, automatic regulation of temperature. Similar convenience is obtained with gas ; but when fire hazard is also considered, the advantage is undoubtedly i This publication is the seventh of a series planned to report the results of investigations conducted by the California Agricultural Experiment Station in cooperation with the California Committee on the Relation of Electricity to Agriculture. This circular supersedes Bulletin 441, ' ' The Electric Brooder. ' ' 2 Associate Professor of Poultry Husbandry and Associate Poultry Husband- man in the Experiment Station. 3 Associate Professor of Agricultural Engineering and Associate Agricul- tural Engineer in the Experiment Station. 2 University op California — Experiment Station with electric heat. Electric brooding, however, involves a number of problems which must be understood and given proper consideration if most effective operating results are to be obtained ; these problems are discussed in detail in the following pages. ELECTRIC BROODING REQUIREMENTS In artificial brooding, certain essential requirements have to be met. Some of the more important are : 1. Sufficient floor space beneath the brooder to prevent crowding. An allowance of 7 square inches per chick and 14 square inches per turkey poult is recommended because these allowances have been found by experience to give most consistently satisfactory results. 2. Sufficient heating capacity to maintain a temperature of 95 degrees Fahrenheit 2 inches above the floor and 5 inches inside the outer edge of the hover. 3. Heating elements so arranged as to give uniform distribution of heat. 4. Automatic, dependable, temperature regulation. 5. Adequate ventilation. 6. Simplicity of brooder design making for ease of operation and ease of cleaning. 7. Durability of construction. NON-GLOWING (BLACK HEAT) 4 TYPES OF BROODERS One of the older types of electric brooder consists of a rather low hover surrounded by curtains and heated by overhead non-glowing heating elements (see fig. 1, and sketch 1, fig. 2). The elements are fastened to the under side of the hover just above the heads of the chicks, and are connected to a thermostatic switch to control the tem- perature. Ventilation is provided by the natural movement of air in and out of the brooder through the curtain due to the difference in temperature between the air under the hover and that of the room. The rate of ventilation is increased or decreased by raising or lowering the hover. Sketch 2 (fig. 2) shows a hover employing overhead, non-glowing elements and fitted with a chimney and damper in the apex of the canopy. Since warm air tends to rise, ventilation is established, but 4 "Black heat" is a term sometimes applied to electric heating elements, which operate at a temperature below the glow point; that is, the wire main- tains its natural color (see fig. 18). Cir. 325] Construction and Operation of Electric Brooders 3 there is a rapid loss of heat because the air can pass directly from the heating elements to the ventilator without first circulating through the hover. Sketch 3 is a further modification of the chimney idea, using a stack which extends down into the brooder, and which may be of one piece or of the telescoping type. The telescoping stack provides a manual adjustment of ventilation. It prevents undue waste of heat. Failure to adjust the stack for changing temperature and moisture conditions, however, may be a source of trouble. Fig. 1. — A simple, wood, non-glowing electric brooder using overhead heat. Note the use of good electric insulation, an ether wafer thermostatic switch, well designed power leads, and the simplicity of construction. (From Bui. 441.) Sketch 4 shows the usual hover employing overhead non-glowing elements, with the addition of an air duct in the floor of the brooder. The purpose of this air duct is to permit an upward flow of fresh air through the floor into the brooder. This duct may not bring about satisfactory ventilation unless a heating element is installed as shown in sketch 6. Sketch 5 shows the usual hover, employing overhead non-glowing elements and equipped with a false floor made of lath covered with burlap. The purpose of this false floor is to prevent floor dampness by means of sub-floor ventilation. University of California — Experiment Station LINE SKETCH NO. i. HEAT: 3/och, Overhead Heating Elements. CONTROL : Thermostat Switch. VENTILATION: Room Cross Currents, Unci, reefed. CURTAINS: Two. ' AIR FLOW. Jn at- One. Side, Out Other Side BROODER FLOOR: Room. HEAT: B/acMj Overhead Heating Elements. CONTROL; Thermostat- Switch. VENTILATION: Semi-directed, Slightly Forced, According to Height of ffac/tfrom Floor. CURTAINS: One. Chimney: Telescoping. AIR FLOW. InofCurtain,OufSlacMjorInat One S/de Oct Other Side- or Both BROODER FLOOR: Room. LINE SKETCH Al£ 2 HEAT: BlacK, Overhead Heating Elements. CONTROL: Thermostat Switch. VENTILATION: Forced, Directed. CURTAINS: One. CHIMNEY: At Apex AIR FLOW: In at Curtain, Out Thru Stacn. BROODER FLOOR: F?oom. HEAT: BIoch, Overhead Heating Elements. CONTROL: Thermostat Switch. VENTILATION: Semi-directed, Slightly Forced, Accord ina to Height of Hover from Floor. CURTAINS: One. FLOOR AIR DUCT: One. AIR FLOW: Jn at Center Air Di/ct, Out Under Curtain; In at One Side ,Out Other j or Both. BROODER FLOOR: Room. tvis. HEAT: BIoch, Overhead Heating Elements CONTROL : Thermostat Switch. VENTILATION: Room Cross Currents, Undirected. CURTAINS: One, or Two. AIR FLOW: In at One Side, Out Other Side. BROODER FLOOR: False Slatted Floor, Covered With Burlap, Standing 2 "above Ffoom Floor. HEA T: B/acfi Overhead Heating Elements. CONTROL: Thermostat Switch. VENTILATION: Forced, Directed. CURTAINS: One. AIR DUCT: One, Center. AIR DUCT ELEMENT: Slowing Coil. AIR FLOW: In at Center Air Duct, Out Under Curtain. BROODER FLOOR : Room. HEAT: Blacn, Overhead Heating Elements. CONTROL: Thermostat Switch. VENTILATION: Room Cross Currents, Undirected. CURTAINS: One FALSE FLOOR ELEMENT: Blacx Heat. AIR FLOW: In at One Side, Out Oth* r BROODER FLOOR: Special Heoted Floor Standing -f" Above Room Floor, A/o Air Duct m 6. HEAT: B/acii Overhead Heating Elements. CONTROL: Thermostat Switch. VENTILATION: Forced, Directed. CURTAINS: One. AIR DUCT: One, or Two. FALSE FLOOR ELEMENTS: Blacn ffeat. AIR FLOW: Under False Floor, Up Thru Duct, Out Under Curtain. BROODER FLOOR: Special Heated Floor. 4" Above Room Floor. Fig. 2. — Line sketches showing different methods which have been employed for heating and ventilating electric brooders. (From Bui. 441.) Cir. 325] Construction and Operation of Electric Brooders mi. HEAT: Glowing or B/ac/r F/oor/ieofihg Elements. CONTROL ! Thermostat Switch. VEAITI LATION: Jemi -directed, Slightly forced. According to Height of Curtain from Floor CURTAINS: One. AIR DUCT: One AIR FLO*/: InThru Tunnel, Out Under Curtain BROODER FLOOR: Room. A/9 11 HEAT: Glowing, Overhead Heating Elements. REFLECTOR: Tin, Concave, 20" Radius, COdTROL: flanual CURTAINS: A/one. VE/VTILA TIO/V: Cross Odrrenh, Undirected. 7 m NilO HEAT: Glowing or Blocn Side Fleo J Elements. CONTROL: Thermostat Switch. VENTILATION: Forced, Directed. CURTAIN5: One. AIR FLOW. In thru Side Vent, Over Partition, Across Brooder, Out Cinder Curtain. BROOOER FLOOR: Room. m\12 HEAT: Glowing, Overhead heating Elements REFLECTOR: Tin, Rt, Vert.,Cone. CONTROL: rionual Fig. 5. — A convex copper heat reflector. Two heating elements are on the ther- mostatic circuit and two are controlled by a hand switch. This type of reflector diffuses the heat, making the complete area under the hover comfortable to the chicks. (From Bui. 441.) 8 University of California — Experiment Station to them if not reflected. The heat reflector, then, plays a very impor- tant part in this type of brooder. Concave and cone reflectors (sketches 11 and 12, fig. 3), concentrate the rays toward the center, tending to cause a "hot spot" to be formed on the brooder floor which constitutes waste floor space, since the heat is too intense for the chicks to remain in this area. This hot-spot condition can be prevented by properly adjusting the height of the reflector from the floor, by using a reflector of correct slope, by lowering the temperature of the wire surface, or by screening the rays. Sketch 13 shows a radiant brooder with a flat reflector which diffuses the rays to some extent. The temperature at the center of the hot spot, due to this diffusion, is slightly decreased and its area increased. Fig. 6. — A concave cone heat reflector sometimes used in glowing type brood- ers. It concentrates the heat rays toward the center tending to create a hot spot on the floor. (From Bui. 441.) Sketch 14 shows a radiant brooder equipped with a convex heat reflector. A convex reflector of small radius diffuses the rays very rapidly, while one of greater radius diffuses to a lesser degree. The radius of curvature should not be less than 20 inches when a hover having a ratio of height to diameter of 1 to 2 is used. Sketch 15 shows a radiant brooder equipped with an inverted right cone reflector. If this type is used, the height of the reflector or cone should be about one-fifth of its diameter. The resulting dif- fusion of the rays then approaches that of the convex reflector of large radius as described under sketch 14. Sketch 16 shows a. radiant brooder equipped with a combination convex and concave reflector. The purpose of this design is to obtain as uniform distribution of heat as possible under the brooder and to prevent the formation of uncomfortable hot spots for the chicks. Cir. 325] Construction and Operation of Electric Brooders 9 The reflector and heating units of a radiant brooder should be at least 2 feet above the floor. No harmful effects upon the chicks from the light of glowing elements have been observed. The reflector should be made of some metal which will not curl or warp when subjected to the heat from the elements. Tinned sheet- iron does very well and when it tarnishes can be given a coat of heat- resistant aluminum paint which increases the reflector efficiency. Copper, brass, zinc, or other metals can also be used but galvanized iron is not desirable since the heat causes the zinc coating to peel off. Fig. 7. — An alleyway brooder house with electric brooders built in. The brooders are built in pairs and their construction is shown in sketch 10 of figure 3. The brooders are a foot above the floor of the alleyway so that fresh air can circulate underneath and enter the fresh air intakes extending through the floor of each brooder. BROODER DESIGN AND CONSTRUCTION Built-in or Portable Brooders. — In figure 7 is shown a very good type of built-in electric brooder. The hover, as indicated, is all in the alleyway and is constructed as shown in sketch 10, figure 3. The top of a built-in brooder situated in the alleyway will not, because of its location, accumulate a coating of droppings and have to be cleaned 10 University of California — Experiment Station at intervals; a brooder that is placed in the room with the chicks requires a top steep enough so that the chickens cannot perch on it. A portable brooder, however, can be constructed with all of the essential advantages of a built-in brooder, and still retain the advan- tages resulting from its mobility (see figs. 8, 9). It can be stored away between seasons. It can be entirely removed from one brooder pen, where the chicks no longer need it, to another pen being pre- pared for a new hatch. Its removal from a brooder room gives unimpeded access to the space it occupied, for the installation of roosts, etc. A special building is not required. It can be used in Fig. 8.— Curtained, portable brooder with a very small slope to the top. The interior of this brooder is shown in figure 12. spare pens, in laying house, or in temporarily available space in a barn or other outbuildings. The factor of portability reduces the investment and adds convenience without necessarily sacrificing any of the real advantages of the built-in type. Curtained or Curtainless Brooders. — A curtain on an electric brooder serves to control ventilation and prevent an undue dissipation of heat (fig. 10). Electric brooders use the natural system of ventilation whereby the inflow of fresh air and the outflow of stale air are brought about by differences in temperature between the air in the brooder and that in the brooder room. The rate of air flow, however, depends not only on such temperature differences but also on the size and location of the ventilation openings. The greater the difference in temperature Cm. 325] Construction and Operation op Electric Brooders 11 between the air of the room and the air in the brooder, and the younger the chicks, other things being equal, the smaller the amount of opening required to ventilate the brooder effectively. If a brooder filled to capacity with newly hatched chicks on the basis of 7 square inches of floor space per chick is operated at a tem- perature of 95° F in a room whose temperature is 50°, and the only way air can enter and leave is under or through a curtain, a space of 1 inch below the curtain will provide good ventilation. As the chicks grow older they consume increasing amounts of oxygen and give off increasing amounts of carbon dioxide. Less heat, from week to week, however, is needed to make them comfortable. Fig. 9. — A portable, curtainless electric brooder using glowing units and a convex heat reflector like that shown in sketch 16 of figure 3. This brooder has two or more circuits, according to the size. One circuit is operated by the thermostatic breaker and the others by hand switches. Note the steep sides and flat top with pilot light. The top is heavily insulated. Lowering the temperature of the brooder as the chicks grow reduces the difference in temperature between the brooder and the room, but retards ventilation. To offset this effect and give the chicks the increased ventilation needed, the canopy can be raised higher from the floor. Since few chicks are under the hover at any one time during the day, however, the canopy can be lowered in the morning and ventilation reduced. Then at night it can be raised again to 12 University of California — Experiment Station supply the ventilation needed when all the chicks are under the hover. This method of raising and lowering the canopy will conserve electric energy and still provide good ventilation (see fig. 11). It is not practicable to set the edge of the canopy of a curtainless brooder lower than 3% or 4 inches above the floor. A curtainless brooder would, therefore, under the brooding conditions described in the previous paragraph, provide excess ventilation, and waste heat. Fig. 10. — Two views of a galvanized-iron, electric brooder, showing low con- struction of hover and arrangement of overhead non-glowing heating elements. It can be placed under the droppings board and either supported on its own legs or suspended from above. The canopy is so flat that chicks can perch on it. The heating elements are wound on asbestos sticks and are fastened to the hover by spring clips. Should the wire on one stick burn out it is easily removed and a new one snapped into place. Note that two heating circuits are connected in parallel, thus assuring some heat should one circuit burn out. (From Bui. 441.) On the other hand, when circulation under the canopy is the only means of ventilation, a curtained brooder must be raised successively higher from the floor as the chicks grow or as the weather becomes warmer. Hence, in the warmer weather of spring, or with older chicks, the curtained brooder may use just as much electricity as a curtainless brooder. It is only in cool weather that a low-set, curtain- Cm. 325] Construction and Operation of Electric Brooders 13 Fig. 11. — A galvanized-iron, electric brooder, using overhead non-glowing elements, and a central ventilating stack. The counter weight at the top of the picture is used to adjust the height of the hover from the floor to regulate ven- tilation. (From Bui. 441.) Fig. 12. — Interior view of an electric brooder similar to the one shown in figure 8. This brooder is so wired that the two heating circuits work in parallel at 110 volts and in series at 220 volts. The change is simply made. The hover is well insulated against heat losses, especially in the central section. (From Bui. 441.) 14 University of California — Experiment Station less brooder is particularly handicapped through a lack of such control of ventilation as a curtain provides. A curtain offers a simple, practical means of regulating ventilation but requires careful opera- tion; omitting the curtain assures ventilation that guards the chicks against mistakes of the inexperienced operator, but may materially increase fuel costs. CONSTRUCTION OF BROODER Heat Capacity or Connected Load. — An electric brooder requires sufficient heating capacity to keep newly hatched chicks warm under the coldest temperature conditions practicable for the operation of such a brooder (see section "Room Temperature"). This capacity, as expressed in number of watts of connected load, is largely influ- enced by the total area of the openings through which air can pass in and out. For example, a curtainless brooder 42 inches in diameter with the edge of the canopy 4 inches from the floor would require a heating capacity of not less than 700 watts to insure ample heat for very young chicks in a room temperature of 40° F. Under like con- ditions a similar brooder with a curtain the bottom of which was only about 1 inch above the floor, would need not more than 400 watts to keep the chicks warm enough (see table 1). This difference in per- formance is due to the difference in the amount of opening under the canopy for ventilation. Quality of Insulation. — One very satisfactory method of insulating a metal canopy is to use two cones having the same basal diameter, but different slopes, so that when one is fitted over the other the edges meet and there is a tapering air space from the edges to the points of the cones. This air space is packed with a good insulating material of light weight. Insulation exerts a direct influence on heating capacity and cost of operation, because of its effect on heat loss through con- duction. The top of the brooder may get decidedly hot if not well insulated. Unless the job of insulating is well done, it may serve only to increase the cost to both the manufacturer and consumer. A sheet of asbestos pasted to the under side of a metal canopy not only provides little insulation, but is soon picked off by the chicks after the brooder is put into use. Kind of Heating Units. — In figure 1 a heating unit made of straight wire strung on porcelain knobs is shown. Instead of using knobs, some manufacturers sew the wire in predetermined patterns into a large asbestos pad which is fastened to the under side of Cm. 325] Construction and Operation of Electric Brooders 15 Fig. 13. — A conical, galvanized-iron brooder, with heating elements cased in concrete. The concrete block is hollow at the center and is connected to the room air by an air duct at the bottom. The air in the center of the block becomes heated and rises, and is replaced by fresh air through the duct. (From Bui. 441.) Fig. 14. — Some representative types of heating units used in electric brooders. In the strip heater and ring unit, the resistance wire is enclosed in a metal sheath, and sometimes imbedded in a plaster-like, refractory material, to increase the durability of the unit. Screw-socket heating units that glow are apt to cause trouble if installed with the threaded receptacle above the wire unit, owing to the effect of the intense heat on the receptacle. The unit consisting of a resistance coil wound on a rod is shown installed in figure 10. It is held by brass contact clips and is easily slipped in or out. 16 University of California — Experiment Station the brooder top. In figure 10 the heating wire is first coiled on asbestos-covered sticks with broad copper rings on each end to serve as terminals. The sticks are held in spring clips and are easily removed for repairs or renewal. Figure 12 shows heating units con- sisting of two strings of coiled resistance wire held in place with porcelain cleats. Figure 5 shows reflectors in which the heating units screw into porcelain lamp sockets. In figure 13 the heating wire is cast in a hollow concrete block to form a massive, heating unit. Other types of units used are strip heaters, and metal-sheathed rings. A variety of heating units is shown in figure 14. Durability of Heating Elements. — Frequent heating to very high temperatures, oxidation from exposure to the air, and fusing because of short circuits, are the principal causes of deterioration in the resist- ance wire used for heating units. This deterioration can be retarded and the useful life of the wire materially lengthened by : 1. Distribution of the connected load among the manually and automatically controlled circuits in such a way as to reduce the opening and closing of the thermostatic breaker to a minimum. The less frequently the breaker opens, the less frequently the heating units in the circuit will be heated and cooled, as pointed out in the discussion of multiple circuits and the distribution of the load. 2. The use of heating units in which the wire does not attain a temperature higher than 932 degrees (see table 2). 3. Proper support of the resistance wire to prevent short circuits due to the lengthening that occurs when it is heated. The runs in straight or coiled open wiring should not be close enough to entail the risk of touching when heated, and should be supported at least every 12 inches. 4. The use of terminals to the heating units which are of good size, have screw connections and are strongly made. Solder joints and screw connections made of too light material are a fertile source of trouble. Number of Circuits and Distribution of Connected Load. — Mul- tiple circuits provide a better method of safeguarding chicks against chilling due to accidental breaks in the heating system than does a single circuit (see fig. 12). If the thermostat controls only one cir- cuit, the failure of this circuit with the hand switches open would result in the complete stoppage of heat production. Such failure would be particularly serious at night. With two circuits on the breaker, the second one would continue to function and provide suffi- Cm. 325 J Construction and Operation of Electric Brooders 17 cient heat to prevent serious injury to the chicks until better provision could be made for them. If part of the heat is controlled by one or more snap switches and part by the thermostatic breaker, the total load should be so divided between the automatically and manually controlled circuits that the desired temperature can be readily maintained at all times. The use of the dual heat control, especially in brooders with a connected load exceeding" 500 or 600 watts, also reduces the current passing" through the automatic breaker and minimizes burning and pitting of breaker points. To cite an extreme case, a certain manufactured brooder was so wired that a heating load of 1,200 watts operated continuously so long as the brooder was connected to the line, and a load of only 300 watts was controlled by the thermostatic breaker. A better method would be to place 500 watts in two circuits on the automatic breaker, 400 watts on one snap switch and the balance of 600 on another. This would provide much more effective temperature regulation and materially reduce operating costs under most conditions. All of the connected load should be under the control of automatic or manual switches. One automatic breaker is sufficient but enough manual switches should be provided to maintain the desired tempera- ture with a minimum opening of the automatic breaker circuit. Sensitivity and Dependability of Automatic Breaker. — The main- tenance of the desired temperature conditions in the brooder depends upon the accuracy with which the thermostat switch functions, and such accuracy in turn depends upon correct design and construction. Silver contacts do not stick or cause trouble from burning if cleaned and trued up occasionally. Very small contacts are damaged more from arcing than larger ones ; whereas the upturned surface of a very large lower contact may catch fine particles of dirt or sand that will hold the contacts apart. Contacts % to %g i nc ^ i n diameter have proved satisfactory. The sensitiveness of a thermostat switch depends on the length of the breaker arm in the bimetallic type, and on both the length of the arm and the number of cells in the wafer type. The longer the arm, or the greater the number of cells in the wafer, the smaller is the rise in temperature above the normal required to open the points of the breaker. Hence, when the movement of the wafer is combined with that of the lever arm, the arm can be shortened. The entire breaker is thus made much more compact and is still kept sensitive enough for the purpose. The cost of a wafer increases with the increase in number of cells. A compact breaker with enough cells to prevent 18 University of California — Experiment Station more than deviation of y 2 degree may be desirable in an incubator, but in a brooder a 2 to 3-degree variation is not objectionable, so that a less costly two-cell wafer can be used satisfactorily. The breaker, as a whole, should be simple and sturdy in design, have a minimum of play at the pivotal points, and be easy to repair. Fuse Protection. — Another feature which adds to the reliability of electric brooders is proper fusing. The main circuits to which brooders are connected are usually properly fused, but the individual brooders rarely are. A broken heating coil falling on a damp con- Fig. 15. — Interior of brooder shown in figure 9. Note attraction light, ether wafer, spun-brass reflector, and heating units with heavy, bolted terminals. Deep grooves in the heating units hold the wire more firmly in place than shallow grooves when it expands on heating. crete floor or otherwise causing a short-circuit might blow a main fuse and thus interrupt the service to a number of brooders. A separ- ate fuse of the proper size on each brooder would guard against service interruption to more than one brooder from any cause within the brooder itself. A simple method is to place a porcelain receptacle in one side of the line and screw in a fuse plug. The fuse plug will also serve as a cut-out. Pilot Lights. — A pilot light is useful in showing that the circuit to which it is connected is functioning (see figs. 8, 9). It makes for convenience in that it is so readily observed. The ideal arrangement Cm. 325] Construction and Operation of Electric Brooders 19 would be to have a pilot lamp in each circuit, but this would increase the cost of brooders having' a number of circuits. The hand-operated circuits are less frequently in use and therefore less subject to oper- ating trouble than those automatically controlled ; hence, there is a greater need for pilot lamps on the breaker circuits. Attraction Lights. — An attraction light in the brooder has been found of considerable value in teaching chicks to use the hover and not stray away into cold corners (see fig. 15). It materially reduces the labor of getting the chicks properly settled under and around the hover at night. The operator can reach into the hover and screw such a bulb in or out of the socket to turn the light on or off, but a snap switch is more convenient. A dim, blue light is satisfactory, and it need be no larger than 10 watts. Methods of Adjusting Height of Brooder. — As previously pointed out in discussing the curtain, it is desirable to regulate the height of a portable electric brooder from the floor. With many of the brooders now on the market this is accomplished by suspending the brooder from one end of a rope running through a ceiling pulley and a counterpoise weight from the other (fig. 11). A sack of sand makes an excellent counterpoise weight. Legs are also provided on nearly all brooders. They are very convenient in fixing a definite minimum height. In a warm rcom the brooder should be raised higher than in a cool room to obtain the same amount of ventilation under the curtain. If the legs are adjustable for length, they will serve to regulate the height of the brooder to a certain extent and postpone the time when rope and pulley are needed. Type of Thermometer and Its Location. — One of the most irritating defects found in many electric brooders is an inaccurate thermometer. Any cheap thermometer will not do. It should be made especially for brooder use; should be accurately graduated; and be of convenient size and shape. In some thermometers the top of the glass tube is finished without projections, whereas incubator thermometers are sealed at the top with a pointed projection at a right angle to the glass tube. This projection fits into a hole in the metal back and so prevents the tube from shifting on the scale. In the cheap brooder thermometer without this pointed projection, the glass tube soon gets loose and slides up and down with handling so that it may give a reading as much as 10° above or below the correct temperature (see fig. 16). A very convenient way to place the thermometer is to suspend it through a hole in the top of the brooder so that it can be easily with- 20 University of California — Experiment Station drawn from the outside. This hole should be near the outer edge of the top. A convenient thermometer mounting; consists of a cylindrical piece of wood about one inch in diameter with the metal-backed ther- mometer set into the side of it, This wooden holder should be long enough to bring the thermometer bulb to within 2 inches of the floor, and to project about 2 inches above the hole in the brooder top to form a handle. A thin metal washer can be slipped over the handle and be fastened to the wood at the proper height to hold the thermometer in position and to seal the hole. y 60: i sot Fig. 16. — An excellent type of brooder thermometer. It is designed for insertion through a hole in the top or side of the brooder so that it can be conveniently reached and read. It should be of such length and so placed that the thermometer bulb is 2 inches above the floor and within 5 inches of the outer edge of the canopy. Shape of Canopy. — The shape of the canopy, or brooder top, affects its cleanliness. Chicks cannot perch on a steeply sloping canopy, whereas one flat enough for them to walk on becomes soiled with droppings and must be cleaned frequently (see figs. 9, 10, 17). It is more difficult, however, to build a steeply sloping top on a wooden brooder than it is to make it flat. Cie, 325] Construction and Operation of Electric Brooders 21 Durability of Construction. — A brooder receives more or less hard service. If permanently built-in; it does not suffer the wear and tear of being moved from place to place, but the usage received from day to day in brooding with any kind of brooder is such that strong, durable construction pays. A well designed and constructed electric brooder may cost more to buy but will cost less per year for depend- able and satisfactory service. Flimsy legs, a thin sheet iron canopy that twists and weaves when moved, very light bracket supports for the thermostatic breaker, and poorly constructed heating units increase depreciation and repairs and decrease operating efficiency. Fig. 17. — Chicks will perch on and soil the top of a brooder that is not steep enough to prevent their standing on it. DETERMINING THE HEATING SPECIFICATIONS FOR AN ELECTRIC BROODER Heat Requirement. — Tinder ordinary operating conditions a curtain-type brooder will require approximately 1.5 to 2.0 watts of heating capacity per chick and a curtainless brooder will need 2.5 to 3.5 watts per chick (see table 1). The higher values are required when brooding is done in cold brooder rooms without the use of auxiliary heat to take the chill from the room, and in small brooders where the number of chicks is small and the space under the edge of the canopy through which heat can escape is greater in proportion to its floor area than it is in larger brooders. 22 University of California — Experiment Station The heating elements of a brooder with a capacity of 300 chicks would, therefore, have a total rating, according to table 1, of : 450 to 600 watts for the curtained brooder, and 750 to 900 watts for the curtainless brooder. The heating elements can be of any suitable type as explained in the section describing different kinds of heating units. TABLE 1 Principal Specifications for Electric Brooders to Operate in Room Temperatures Above 40° F Capacity Area square inches Diameter if circular, inches Side if square, inches Heat capacity or connected load, watts Electricity required to brood chicks to 6 weeks, kilowatt-hours Turkey poults* Chicks Curtained Curtainless Curtained Curtainless 100 200 300 462 582 50 100 700 1,400 2,100 3,216 4,072 30 42 52 64 72 27 37 46 57 64 150- 200 300- 400 450- 600 700- 925 875-1,164 250- 350 500- 700 750- 900 1,100-1,350 1,350-1,700 50-100 100-200 i 50-300 225-450 300-600 100- 200 200- 400 300- 600 500- 900 600-1 , 100 * It is not advisable to brood turkeys in groups of more than 100. Size and Length of Resistance Wire. — Let us assume that the cur- tained brooder is to have a total heating capacity of 600 watts in two circuits of 300 watts each, and the curtainless brooder a capacity of 900 watts in two circuits of 450 watts each. Then, the current in amperes and the total resistance of the heating system in ohms must be determined from the following formulas, volts and watts being known : watts Using a current with a voltage of 110, and since amperes 300 volts' then or 110 450 110 2.73 amperes, for the curtained brooder; = 4.09 amperes, for the curtainless brooder. Using these two values the total resistance of each circuit is found volts as follows : since ohms = 110 2.73 110 amperes , then or = 40.3 ohms, for the curtained brooder ; = 26.9 ohms, for the curtainless brooder. 4.09 The person constructing the brooder must also decide if the ele- ments are to operate at a glowing or non-glowing temperature (see section "Durability of Heating Elements"). If they are to glow, the Cm. 325] Construction and Operation of Electric Brooders 23 degree of glow must be decided. Resistance wire assumes colors with corresponding temperatures as indicated below Color of wire Black or natural Faint red Blood red Cherry red Bright red Temperature, degrees Fahrenheit to 800 800 to 1,050 1,050 to 1,150 1,150 to 1,300 1,300 to 1,600 It is here assumed that the curtained brooder will use ''black" heat with a wire surface temperature of 572° F and the curtainless brooder will have glowing or faint red heating units with a wire surface temperature of 932°. TABLE 2* .Resistance, Current, and Temperature Characteristics of "Niciirome IV" Resistance Wire, with Specific Resistance of 650 ohms Per Circular Mil Foot at 68° F Wire size, Diam- eter of wire, inches Resis- tance in ohms per foot at 68°F Amperes necessary to produce temperatures listed below B. &S. gauge 392° F 572° F 752° F 932° F 1,112°F 1,292° F 1,472° F 1,652° F 1,832° F 10 0.102 0624 19.5 25 4 30 9 37.1 43.7 51.0 57.7 65.6 74 4 11 0.091 0784 16.5 21.5 26.1 31.4 36.9 43 48.6 55 3 62.6 12 0.081 0990 14 18.2 22.1 26.6 31.3 36.5 41.3 47.0 53 2 13 0072 0.1253 11.8 15 3 18.2 22 5 265 30 9 35.0 398 45.0 14 0.064 0.1586 10 13.0 15.9 19.0 22 5 26.1 29.6 33 .7 38.1 15 0.057 2000 8 50 111 13.5 16.2 19.0 22.2 25.1 28.5 32.3 16 0.051 2499 7.20 940 114 13.7 16.2 18.8 21 4 24 3 27.5 17 0045 3209 6.10 7.95 965 11.6 13.7 15.9 18.1 205 23.2 18 040 0.4062 5 18 6.73 8.20 985 11.6 13.5 15.3 17.4 19.7 19 0.036 5015 4.37 5.70 6.95 8 35 985 114 12 9 14.7 16.7 20 032 6347 3 70 4.80 585 7.05 8.30 9. 70 10.9 12 4 14.1 21 0285 08002 3 13 4 07 4.95 5.95 7.05 8.15 9.25 10 5 11.9 22 0253 1.015 265 3.45 4.20 5.05 5.95 6.95 7.85 8.90 10.1 23 0.0226 1.272 226 2.84 357 4.30 5.06 5.90 6.67 760 8.60 24 0.020 1.S25 1.91 2.48 3 02 3.64 4.27 497 5.63 6 40 7.25 25 0179 2.028 1.62 2.10 255 3 08 3.64 4 23 4.80 5.45 6.13 26 0.0159 2.571 1.37 1.78 217 2.60 3.07 3.57 4 05 4.60 5.20 27 0142 3.223 1.16 1.51 184 2 21 2.61 3 04 3.44 3 90 4.42 28 0.0126 4.094 1.00 1.29 1.58 1.89 2 23 2.60 2.94 3.35 3.89 29 0.0113 5.090 086 1.11 1 35 1.62 1 92 2.23 2.52 2.95 3 25 30 0.010 6.500 073 0.95 1.17 1.40 1.65 192 2.17 2.47 2.80 31 0.0089 8.206 63 0.82 1.00 1.20 1.41 1 65 1.86 2.12 2 40 32 0.008 10.15 54 0.70 086 1.03 1.21 1.42 1.60 1.82 2.06 33 0.0071 12.89 0.46 60 074 88 1.04 1.21 1.37 1.56 1.77 34 0063 16.37 0.40 0.52 0.63 0.77 0.90 1.04 1.18 1.34 1.52 35 0.0056 20.72 34 0.45 54 65 0.77 0.89 1.01 1 15 1.30 36 0.005 26.00 29 38 47 056 066 77 87 99 1.12 37 0.0045 32.09 25 33 40 0.48 57 66 75 0.85 96 38 0.004 40 62 0.21 28 34 0.41 49 57 64 73 0.82 39 0035 53.06 18 0.24 29 0.35 0.41 0.49 54 62 70 40 0031 67.63 16 0.20 25 30 0.35 41 0.46 0.53 0.60 * Adapted from tables by Driver-Harris Company, Detroit, Michigan. Similar tables can be obtained from the manufacturers for other makes or grades of resistance wire. The data are for straight wire in air, in a horizontal position. 24 University of California — Experiment Station Reference is now made to table 2 in order to find what size of wire will carry 2.73 amperes at a surface temperature of 572° F and 4.09 amperes at 932° respectively. Opposite wire number 23 under the column headed 572° appears 2.84 amperes and under the column headed 932° appears 4.30 amperes, so that No. 23 wire will do for both cases. The length of this wire must be such as to give a total resistance of 40.3 ohms for the curtained brooder and 26.9 ohms for the curtain- less brooder, as determined above. The resistance per foot for each wire is given in column 3, table 2, but must be corrected as shown below because the resistance changes as the wire heats. Temperature, wire surface, degrees Fahrenheit Correction factor 5 68 1.0000 212 1.0051 392 1.0250 572 1.0400 752 1.0490 932 1.0530 1,112 1.0480 1,292 1.0440 1,472 1.0460 1,652 1.0550 Using the correction multiplier of 1.04 for 572° and 1.053 for 932°, it is found that No. 23 wire has a resistance of 1.272 X 1.04 or 1.323 ohms per foot at 572° and 1.272 X 1.053 or 1.34 ohms at 932°. The length required is then found by dividing the corrected resistance per foot into the total resistance, viz. : 40.3 ~- 1.323 = 30.5 feet of No. 23 wire for the curtained brooder, and 26.9 ~ 1.34 = 20.1 feet of No. 23 wire for the curtainless brooder. The complete information needed to construct a 300-chick capacity curtained brooder to operate at black heat on a 110-volt circuit and a curtainless brooder at 300-chick capacity to operate at a glowing wire temperature of 932° F is assembled in table 3. The length of wire can also be obtained directly from the chart in figure 18. The intersection of the horizontal lines corresponding to 300 watts with the curve for No. 23 wire gives the length, as shown by the vertical lines, of about 30.6 feet at a temperature between 392° and 540° F. That for 450 watts gives an approximate length of 20.1 feet for No. 23 wire for a temperature a little less than 932° F. s Adapted from tables published by the Driver-Harris Company of Detroit for Nichrome resistance wire with a specific resistance of 650 ohms per circular mil foot at 68° F. Cm. 325] Construction and Operation of Electric Brooders 25 TABLE 3 Specifications for Brooders of 300-Chick Capacity as Computed from Tables Kind of brooder Diam- eter of brooder, inches Number of circuits Wattage per circuit required Current in circuit, amperes Wire tempera- ture Size of wire B. & S. Length of wire per circuit, feet Fuse required, amperes Curtain, non-glow Curtainless, glow- 52 52 2 2 300 450 2.73 4 09 572° F 932° F 23 23 30 5 20.1 10 10 OPERATING AN ELECTRIC BROODER Ventilation and Humidity. — The air breathed in by the chick is warmed and brought into intimate contact with the mucous lining of the air passages, while oxygen is being taken from it. When exhaled, it not only contains carbon dioxide but is also heavily charged with water vapor. The fresh droppings, as they dry, also contribute to the moisture content of the air. When the chicks are in the brooder they are therefore constantly producing moisture which must be removed by ventilation. The quantity of water in the form of vapor that air will hold per unit volume is doubled with a rise in temperature of 22° to 25° F, and is halved with a similar fall in temperature, within the range met with in brooding chicks. For example, every cubic foot of air at a room temperature of 60° F entering an electric brooder at an auto- matically maintained temperature of 85°, even though saturated when it enters, can, when heated to the hover temperature, absorb approxi- mately 100 per cent more moisture than it contained when it entered. It can absorb more than this amount if its relative humidity, when it enters the brooder, is below 100 per cent. Condensation of moisture in an electric brooder (which is commonly called "sweating") occurs only when the moisture given off by the chicks is in excess of what the air will take up and remove. The rate at which the moisture is removed, however, depends on the rate at which the air passes through the brooder. The need for fresh air increases as the chicks grow, whereas, the need for artificial heat decreases. Therefore, the ventilation openings should be enlarged from week to week to produce a sufficient flow of air through the brooder to meet the growing needs of the chicks 26 University of California — Experiment Station and keep the hover dry. Probably the most practical means of accom- plishing this is by diffusion through and under a curtain. The effec- tiveness of this method of ventilation will depend largely upon the height of the curtain above the floor in relation to (1) the number of chicks under the hover contaminating the air, (2) the size of these chicks, and (3) the difference in temperature between room and brooder. In a detailed study 6 at this Station of the relation of ventila- tion in an electric brooder to the health and growth of chicks, as little as 2 cubic feet per minute per 100 chicks proved as satisfactory, up to 6 weeks of age, as larger amounts. Dampness under the hover, even though slight, is evidence of the need for increased ventilation. Brooder Temperature. — A brooder is heated to make chicks in it comfortably warm. Therefore the actions of the chicks are the most important indication of proper temperature conditions. When chicks crowd together they are cold. They spread out when they are com- fortable. A reading of 95° F with the thermometer bulb 2 inches above the floor and 5 inches in from the outer edge of the hover will usually be found satisfactory for baby chicks until they are a week old. Then the temperature should be gradually lowered at the rate of about 4 degrees a week till artificial heat is no longer required. Boom, Temperature. — Newly hatched chicks must not only be kept warm and comfortable but they must be taught to eat. If the room is too cold the chicks will "hug the hover" and not come out. Oil, gas, and coal-heated brooders exert more of an effect on the tempera- ture of the room than do those using electricity; and curtained brooders have less effect than those without curtains. In electric brooders with attraction lights, the water jars and feed receptacles can be placed inside or partly inside the hover for the first few days provided it is not loaded tco heavily with chicks. Another method which helps to overcome the handicaps of a cold room while the chicks are being taught to eat and are gaining the strength to cope with cool temperatures, is to use a tight fence instead of one of open construction around the brooder to keep the chicks from straying into cold corners and getting chilled before they have learned to return to the hover for warmth. If made of such material as burlap-covered netting, roofing paper, or sheet metal, and placed about a foot away, this fence will sufficiently retard the dissipation of the warm air escaping under the canopy to materially raise the temperature of the small feeding space thus provided. It may be necessary temporarily to raise a curtained brooder higher than is 6 Unpublished data. Cm. 325] Construction and Operation of Electric Brooders 27 required for good ventilation in order to have enough heat escape through the curtain. A third method is to place a temporary enclosure around the brooder for the first week. If a laying house is used for brooding, such an enclosure is readily made by placing the brooder under the droppings board in one corner of the room and using light panels of transparent or translucent material to enclose a space 2 to 3 feet larger than the brooder itself. In very cold weather a small, electric room heater can, if necessary, be used to supplement the brooder in warming this enclosure during the day when the chicks are feeding. It will be found advisable, however, to use auxiliary heat to warm the room if much cold weather brooding is to be done with electric brooders. For the first week after the chicks are put in the brooder, a room temperature of not less than 50° F during the day is desirable. Rooms with tight walls and ceiling can be more easily heated than unceiled rooms with wire partitions. Furthermore, it is necessary to heat only the particular ceiled room or rooms being used, whereas, in an open brooder house with many pens, to warm the air of any one pen it would be necessary to heat the entire house. Ceiled rooms therefore permit a more economical use of heat to warm them for cold-weather brooding, when only a portion of a long brooder house is used at a time. Servicing the Brooder. — In getting an electric brooder ready to receive chicks, it should be set up in the brooder room and carefully inspected. If the thermostat is of the ether wafer type, the wafer should be removed and tested. It is advisable to keep an extra ether wafer on hand to replace the one in the brooder should that one give out during a brooding period. A magneto file and a few short %-inch brass bolts with double brass or copper washers should also be kept on hand. The file is needed to clean and square the breaker points. Corroded points may reduce or stop the flow of current. The bolts are used to repair any break that may occur in the wire of the heating units. Twisting the broken ends of the wire around the bolt between the two washers and then screwing the nut on very tightly so that the wires are held in firm contact will give a tight connection that should hold up a long time in brooders using black heat. In the case of a glowing element a break anywhere but at the ends of the wire can best be remedied by replacing the element, as repaired breaks usually do not last long. If the break is at either end of the wire where it is connected to a binding post, a new connection can generally be made. After the brooder has been checked over 28 University of California — Experiment Station J) ^ Vi 1 / 7 _/a 1 * *t mil! ^ ^ Q 1 ^J V, S C 6, * % " / / / I i £j s,. J / / siV / 1 ^ / < / V*> >< 1 N? TJTT 1* / / / N J 1 u V / / / r\ \ I / S k / b- / / \ J £ & Jf /<* M ^> / aJ \j i HI. s %, ^. 4 ^ / , J ■^\ / -) / r J» ->c> / -^ < / / v| < \j s / > < *> ^y $ cj SA/ ~JP / \ jg« r^ggZL ZfJ* <#& t»S J* -* I :|: 1- T >* ' % ^ J ^ ■^1/ t $ L| IP : 8 i i\ § 1 u o «H 8 1 O 1 ^ u ^ ^ o ^1^ > > ^ 2 ^ -^ S f| .2 be 80 fl a; .a § 5 o v ^ fl eS "5i « * "S M -vj aS o ^ N ■in rd 1» 0) «fl ® - r; s> "^ - ^* ^. bfi S ^//Qf OSS/* WW Cm. 325] Construction and Operation op Electric Brooders 29 and any necessary repairs and adjustments made, it should be oper- ated for a day or more to set the thermostat to the correct temperature for the chicks and to be sure that the heating system is functioning satisfactorily. BROODING TURKEYS, DUCKS, AND GAME FOWLS ELECTRICALLY Young turkeys, ducks, pheasants, quail, etc. can be brooded under electric brooders just as successfully as young chickens, provided the rearing methods used are adapted to the peculiarities of the particular species being reared. Game birds do best when brooded in small groups (see fig. 19). For this reason brooders 36 inches or less in Fig. 19. — Specially designed, electric brooders used to brood small lots of pheasants, quail, and other game birds. The brooder room and run are shown in the background. diameter are most commonly used. Most satisfactory results are obtained with turkey poults when not more than 100 are brooded together under one hover and, as previously mentioned, a floor space of 14 square inches per poult is provided. Ducks also thrive better when brooded in groups of 100 or less and are allowed a floor space similar to that for turkey poults. SAFETY PRECAUTIONS In working with any electrical circuit, it is well to remember the following : One should never attempt to work with a "hot" or live circuit, The circuit switch should first be opened and the circuit fuses removed. While 110 volts will usually not injure one, there are conditions under which it may be dangerous. 30 University of California — Experiment Station All electric wires should be considered "hot" until one knows definitely that the circuit is open. One should never work with a power circuit when standing on wet ground or wet floors. One should always remember that both legs of an alternating current circuit, as usually operated, are live. Both legs of each circuit should be fused for about 125 per cent of full load. Knife switches, except in safety boxes, and bare wires are unsafe. For further details relating to the installation of electrical wiring and apparatus, the reader is referred to the Electrical Safety Orders issued by the Department of Industrial Relations and Division of Industrial Accidents and Safety, State of California. STATION PUBLICATIONS AVAILABLE FOE FEEE DISTEIBUTION BULLETINS No. 253. 263. 279. 283. 310. 331. 343. 348. 349. 357. 361. 364. 369. 370. 371. 373. 374. Irrigation and Soil Conditions in the Sierra Nevada Foothills, California. Size Grades for Ripe Olives. Irrigation of Rice in California. The Olive Insects of California. Plum Pollination. Phylloxera-Resistant Stocks. Cheese Pests and Their Control. Pruning Young Olive Trees. A Study of Sidedraft and Tractor Hitches. A Self-Mixing Dusting Machine for Applying Dry Insecticides and Fun- gicides. Preliminary Yield Tables for Second- Growth Redwood. Fungicidal Dusts for the Control of Bunt. Comparison of Woods for Butter Boxes. Factors Influencing the Development of Internal Bi'owning of the Yellow Newtown Apple. The Relative Cost of Yarding Small and Large Timber. Pear Pollination. A Survey of Orchard Practices in the Citrus Industry of Southern Cali- 379 386 389 392, 393, 394, 395. 396. 404. 406. 407. 408, 409, 410. 416. 417. 418. 419. 420. 421. 423. 425. 426. 427. 428. 431. 432. California. Deciduous Fruit fornia. Walnut Culture, in Pruning Bearing Trees. Berseem or Egyptian Clover. Fruit Juice Concentrates. Crop Sequences at Davis. I. Cereal Hay Production in California. II. Feeding Trials with Cereal Hays. Bark Diseases of Citrus Trees in Cali- fornia. The Mat Bean, Phaseolus Aconitifolius. The Dehydration of Prunes. Stationary Soray Plants in California. Yield. Stand, and Volume Tables for White Fir in the California Pine Region. A ltern aria 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 Quality of Fresh Asparagus After It is Harvested. 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. Apricots (Series on California Crops and Prices). Apple Growing in California. Apple Pollination Studies in California. The Value of Orange Pulp for Milk Production. The Relation of Maturity of California Plums to Shipping and Dessert Quality. Raisin By-Products and Bean Screen- ings as Feeds for Fattening Lambs. Some Economic Problems Involved in the Pooling of Fruit. No. 433. Power Requirements of Electrically Driven Dairy Manufacturing Equip- ment. 435. The Problem of Securing Closer Rela- tionship between Agricultural Devel- opment and Irrigation Construction. 439. The Digestibility of Certain Fruit By- Products as Determined for Rumi- nants. Part II. Dried Pineapple Pulp, Dried Lemon Pulp, and Dried Olive Pulp. 440. The Feeding Value of Raisins and Dairy By-Products for Growing and Fattening Swine. 445. Economic Aspects of the Apple In- dustry. 446. The Asparagus Industry in California. 447. A Method of Determining the Clean Weights of Individual Fleeces of Wool. 448. Farmers' Purchase Agreement for Deep Well Pumps. 449. Economic Aspects of the Watermelon Industry. 450. Irrigation Investigations with Field Crops at Davis, and at Delhi, Cali- fornia, 1909-1925. 452. Economic Aspects of the Pear Industry. 454. Rice Experiments in Sacramento Val- ley, 1922-1927. 455. Reclamation of the Fresno Type of Black-Alkali Soil. 456. Yield, Stand and Volume Tables for Red Fir in California. 458. Factors Influencing Percentage Calf Crop in Range Herds. 459. Economic Aspects of the Fresh Plum Industry. 462. Prune Supply and Price Situation. 464. Drainage in the Sacramento Valley Rice Fields. 465. Curly Top Symptoms of the Sugar Beet. 466. The Continuous Can Washer for Dairy Plants. 467. Oat Varieties in California. 468. Sterilization of Dairy Utensils with Humidified Hot Air. 469. The Solar Heater. 470. Maturity Standards for Harvesting Bartlett Pears for Eastern Shipment. 471. The Use of Sulfur Dioxide in Shipping Grapes. 472. Adobe Construction. 473. Economic Aspects of the Sheep In- dustry. 474. Factors Affecting the Cost of Tractor Logging in the California Pine Region. 475. Walnut Supply and Price Situation. 476. Poultry Houses and Equipment. 477. Improved Methods of Harvesting Grain Sorghum. 479. I. Irrigation Experiments with Peaches in California. II. Canning Quality of Irrigated Peaches. 480. The Use, Value, and Cost of Credit in Agriculture. 481. Utilization of Wild Oat Hay for Fat- tening Yearling Steers. 482. Substitutes for Wooden Breakpins. 483. Utilization of Surplus Prunes. 484. The Effects of Desiccating Winds on Citrus Trees. 485. Drying Cut Fruits. 487. Asparagus (Series on California Cropi and Prices). BULLETINS— (Continued) No. 488. Cherries (Series on California Crops and Prices). 489. Irrigation Water Requirement Studies of Citrus and Avocado Trees in San Diego County, California, 1926 and 1927. 490. Olive Thinning and Other Means of Increasing Size of Olives. 491. Yield, Stand, and Volume Tables for Douglas Fir in California. 492. Berry Thinning of Grapes. 493. Fruit Markets in Eastern Asia. 494. Infectious Bronchitis in Fowls. 495. Milk Cooling on California Dairy Farms. 496. Precooling of Fresh Fruits and Tem- peratures of Refrigerator Cars and Warehouse Rooms. 497. A Study of the Shipment of Fresh Fruits and Vegetables to the Far East. 498. Pickling Green Olives. 499. Air Cleaners for Motor Vehicles. 500. Dehydration of Grapes. 501. Marketing California Apples. 502. Wheat (Series on California Crops and Prices). 503. St. Johnswort on Range Lands of California. 504. Economic Problems of California Agri- culture. (A Report to the Governor of California.) No. 505. The Snowy Tree Cricket and Other Insects Injurious to RasDberries. 506. Fruit Spoilage Disease of Figs. 507. Cantaloupe Powdery Mildew in the Imperial Valley. 508. The Swelling of Canned Prunes. 509. The Biological Control of Mealybugs Attacking Citrus. 510. Olives (Series on California Crops and Prices). 511. Diseases of Grain and Their Control. 512. Barley (Series on California Crops and Prices). 513. An Economic Survey of the Los Angeles Milk Market. 514. Dairy Products (Series on California Crops and Prices). 515., The European Brown Snail in Cali- fornia. 516. Operations of the Poultry Producers of Southern California, Inc. 517. Nectar and Pollen Plants of California. 518. The Garden Centipede. 519. Pruning and Thinning Experiments with Grapes. 520. A Survey of Infectious Laryngotrache- itis of Fowls. 521. Alfalfa (Series on California Crops and Prices). CIRCULARS No. 115. Grafting Vinifera Vineyards. 178. The Packing of Apples in California. 212. Salvaging Rain-Damaged Prunes. 230. Testing Milk. Cream, and Skim Milk for Butterfat. 232. Harvesting and Handling California Cherries for Eastern Shipment. 239. Harvesting and Handling Apricots and Plums for Eastern Shipment. 240. Harvesting and Handling California Pears for Eastern Shipment. 241. Harvesting and Handling California Peaches for Eastern Shipment. 244. Central Wire Bracing for Fruit Trees. 245. Vine Pruning Systems. 248. Some Common Errors in Vine Pruning and Their Remedies. 249. Replacing Missing Vines. 253. Vineyard Plans. 257. The Small-Seeded Horse Bean (Vicia faba var. minor). 258. Thinning Deciduous Fruits. 259. Pear By-Products. 261. Sewing Grain Sacks. 262. Cabbage Production in California. 265. Plant Disease and Pest Control. 269. An Orchard Brush Burner. 270. A Farm Septic Tank. No. 279. The Preparation and Refining of Olive Oil in Southern Europe. 282. Prevention of Insect Attack on Stored Grain. 288. Phylloxera Resistant Vineyards. 290. The Tangier Pea. 292. Alkali Soils. 294. Propagation of Deciduous Fruits. 296, Control of the California Ground Squirrel. 301. Buckeye Poisoning of the Honey Bee. 304. Drainage on the Farm. 305. Liming the Soil. 307. American Foulbrood and Its Control. 308. Cantaloupe Production in California. 310. The Operation of the Bacteriological Laboratory for Dairy Plants. 316. Electrical Statistics for California Farms. 317. Fertilizer Problems and Analysis of Soils in California. 318. Termites and Termite Damage. 319. Pasteurizing Milk for Calf Feeding. 320. Preservation of Fruits and Vegetables by Freezing Storage. 321. Treatment of Lime-induced Chlorosis with Iron Salts. 322. An Infectious Brain Disease of Horses and Mules (Encephalomyelitis). 18m-6,'32