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Primus interpares – first among equals! Unexcelled. The USDA for a hundred years has not been excelled by any other Federal agency in the productivity of the research conducted in its laboratories nor the research it has supported in State Experiment Stations and in other cooperating institutions. This assertion is true of poultry research: primus interpares.

Data for individual feed intake, liveweight, and egg production were recorded for five genetically different groups of 40 pullets each during 10 test periods of 28-days each. Average ambient temperature at cage level varied from 6.7 C during January to 21.1 C during June. A 2890 kcal/kg metabolizable energy (ME) diet with 16% crude protein (CP) was fed ad lib. Average egg production for the Small Leghorns (SL) was about 60%, for white-egg hybrids (WL) about 75%, for brown-egg hybrids (BL) about 72%, for female line broiler breeders (BB) about 48%, and for broiler-cross pullets (B) about 51%. Average grams liveweight and grams feed intake per hen day were: SL, 1426 and 83.7; WL, 1809 and 104.9; BL, 2610 and 122.9: BB, 4197 and 156.2; and B, 4158 and 167.7. Partition equations which describe the data for SL, WL, BL, and BB, assuming 70% efficiency of use of feed ME for maintenance, tissue formation, and egg formation were: F = (.534 − .004T)W .653 + 2.76ΔW + .80EM and F = (.259 −.00259T)W.75 + 2.76ΔW + .80EM. Similar equations for B, assuming 65% efficiency use of ME, are: F = (.589 − .0044T)W.653 + 2.9ΔW + .85EM and F = (.275 − .00275T)W.75 + 2.9ΔW + .85EM. The terms are: F = grams feed/hen day; T = ambient temperature in °C; W = grams liveweight; ΔW = grams daily change in liveweight; EM = grams egg mass per hen day. Equations which assume 70% efficiency of use of ME are shown to predict feed intake of a diet containing 2890 kcal of apparent ME per kilogram for white and brown-egg layers and broiler-breeder pullets varying in individual body weights from about 1 to 5 kg. Equations, assuming 65% energetic efficiency, describe feed intake for a group of broiler-cross pullets.

THE malposition, head-under-left-wing, affects from one to about 20 percent of the chick embryos which live through the first eighteen days of the incubation period. The incidence of the malposition has been described by Hutt (1929), Smith (1930), Hale (1930), Byerly (1930), Byerly and Olsen (1931), Hutt and Cavers (1931), and Taylor, Gunns, and Moses (1933). Byerly (1930), stated that the malposition was of doubtful importance as a bar to hatching. Data collected since that time have removed all doubt that it is usually lethal. Several factors which contribute to this lethal effect have been found. First, the malposition is often accompanied by obvious malformation and smallness of the affected embryos. Second, Hutt (1929) pointed out that the beaks of affected embryos are usually turned away from the air cell and that this may reduce the likelihood of pipping. Third, the direction of rotation of the body of the embryos . . .

INTRODUCTION BROODINESS has been greatly reduced in all strains of chickens bred for egg production. There is general agreement that elimination of this inherited trait is one of the quickest and surest steps in increasing annual production. Hays and Sanborn (1928) reported that during the pullet year relatively fewer Rhode Island Reds broody before July 1 died after that date than birds not broody before July 1. Further evidence that the elimination of this natural phase of the reproductive cycle may result in decreased vigor was presented by Hogsett (1941). He reported that among his 1939 flock of 1,896 pullets, 105 were broody one or more times during their first laying year. Survival through the first laying year among these broody pullets was 87.6 percent while survival among the 1,791 nonbroody pullets was 74.2 percent. Now it may be reasoned that some of the so-called nonbroody pullets which died would . . .

For use as assay animals male chicks have the advantage of being relatively cheap and usually available. Moreover, they require a minimum of care and the equipment used is inexpensive. Quantitative measurement of the sensitivity of the chick testis to gonadotropic hormone will make possible its use in assays of gonadotropic potency. The reports of numerous investigators have shown that the chick testis responds to administered gonadotropic hormone from various sources by rapid weight increase. The response to hormone from pituitary preparations and pregnant mare serum is known to be greater than that to hormone from pregnancy urine preparations. Asmundson, Gunn and Klose (1) and Breneman (2) have made recent reports of a qualitative nature, and these papers may be consulted for references to previous work.

FACTORS affecting the incidence of malpositions are of considerable practical importance as well as scientific interest. Embryos in malpositions are less likely to hatch than those in normal position, especially under adverse circumstances. Six malpositions are described in the literature and combinations of several of these occur. It would be possible to subdivide still further the data on position at hatching time but there is probably no rational advantage in doing so. The material presented in the present paper is classified only in the four malpositions described by Hutt (1929) and “other dead,” which includes the normal hatching position. These four malpositions are: I, head between legs; II, head in small end of egg; III, head under left wing; IV, beak away from air cell. The data presented indicate that malpositions I and III are of common origin, and that malpositions II and IV are also of common origin but . . .

Summary and ConclusionsAbnormal embryos and chicks, with relatively short bones, were frequently produced in eggs laid by birds which received diets lacking in some factor or factors present in wheat germ, liver, and whey. The activity, amount or utilization of this factor or these factors was augmented by permitting the birds access to direct sunlight and green range.

IN A PREVIOUS paper (Byerly and Quinn, 1936) it was shown that 47.5 percent of 1,102 Rhode Island Red chicks hatched at the National Agricultural Research Center, Beltsville, Maryland, carried black spotting on the head or black striping on either head or body, also that 42.1 percent of 663 chicks from an excellent standard bred flock carried spotting or striping, indicating that these characteristics may be rather widely distributed among Rhode Island Red flocks. It was further shown that 84.9 percent of the striped or spotted Beltsville chicks were females, whereas 77.8 percent of the non-spotted, non-striped chicks were males. Several breeders and hatcherymen have questioned the extent of the distribution of the characteristics mentioned above. They have also pointed out that little melanic pigment (black spotting and striping) appears in the Rhode Island Red Chicks shown in commercial and standard bred exhibition classes. It was the opinion of the . . .

THIS paper presents the results of one phase of a group of experiments and observations to determine the causes of malposition in chick embryos at hatching time. Malposition is one of the chief immediate causes of embryo mortality in the domestic fowl and is therefore a matter of very considerable economic importance as well as scientific interest. Hutt (1929) suggested that early orientation might affect hatching position and Taylor (1932) found such a relation for the malposition head in small end of egg. LITERATURE For more than a century investigators in biology have known that when the blunt end of the fertile egg of a bird, incubated for a few days, is held to the left of the observer and the upper portion of the shell removed, the embryo usually will be found lying on its left side with the head turned to the right and pointing away from the . . .

APPROXIMATELY one-half of the fertile eggs which fail to hatch in any lot of eggs set contain chicks which have nearly completed development. About half of these, or one-fourth of all the fertile eggs which have failed to hatch, contain chicks in one or more of several malpositions. Thus, in a lot of eggs 60 percent of which hatch, the number of chicks affected by malpositions is about 10 percent of the fertile eggs set. It is obviously of very great economic importance to know to what extent the several malpositions are lethal to the affected chicks. It is the object of the present paper to present new data on the lethality of malpositions and to scrutinize the data and opinions found in the literature. It was supposed by Sanctuary (1925) that malposition 1 I is always lethal; he stated that chicks in other malpositions sometimes hatch. Hale (1930) expressed the . . .

ALTHOUGH many phases of the calcium metabolism of the chicken have been studied, very little attention has been given to the effect of the calcium and phosphorus content of the diet of laying pullets and hens on the production and hatchability of eggs. The purpose of this paper is to present data on this phase of the calcium and phosphorus metabolism of the chicken. These data demonstrate the deleterious effect, hitherto unsuspected, of a high level of calcium intake of laying chickens on the ability of their eggs to hatch, and they suggest that in practical poultry husbandry it is very desirable to control the calcium intake of laying chickens. LITERATURE Wheeler (1919) made many inorganic analyses of the shells of eggs and of the carcasses of chickens and ducks that had received calcium, magnesium, and strontium from several sources as supplements to their diet. He found that the diets . . .

THE data presented by Byerly and Olsen (1931) indicated that from 2 to 3.5 percent of all fertile eggs incubated contain at hatching time dead chicks with their heads in the small instead of the large end of the shell. In order to save the poultry industry the very large sums lost through this means, it is necessary to know the causes for this malposition and the portion of the incubation period during which those causes act. Byerly and Olsen (loc cit.) demonstrated that gravity is a very important factor in determining the hatching position of the chick embryo. The present experiments were designed to give information about the time of determination of the malposition head-in-small-end-of-egg and the mechanism of its determination. Data have been gathered coincidentally on the lethality of this malposition. MATERIAL AND METHOD Several lots of eggs were incubated for various periods in some one of the . . .

POULTRYMEN have long recognized that egg production can be increased during the fall and winter months by artificially lengthening the daily light period. Whetham (1933) correlated the seasonal rates of egg production of hens kept in latitudes throughout the world with the seasonal variations in length of daylight for these same latitudes. It was concluded that the light supply is an important factor in the seasonal distribution of egg production. It is only within recent years that the factors responsible for the striking physiological effect of increased light have been subjected to experimental investigation. It has been quite convincingly established that light stimulates the anterior pituitary gland which in turn releases the hormones necessary for gonadal development and functions. The extensive literature pertaining to this subject has been reviewed by Rowan (1938) and Bissonnette (1936). Penquite and Thompson (1933) reported the use of continuous lights on Leghorns and emphasized the . . .

Sanctuary, (1925), Hutt (1929), Smith (1930), Hale (1930), and Byerly (1930), have reported and discussed data on malposition in the chick embryo, but no experimental work on the cause of malposition has come to the author’s attention. The present paper is presented as a contribution to the solution of the causes of malposition and to our knowledge of its importance as a factor in hatchability. During the earlier portion of the incubation period the embryo floats freely on the upper surface of the yolk. As incubation proceeds, the embryo turns to a new position relative to the overlying shell whenever the egg is turned. If the egg stands on end, this statement must be somewhat qualified because the ehalazae prevent the embryo from reaching the middle of the upper yolksurface. Since the position of the embryo in the egg is at first determined by gravity, it is reasonable to suppose . . .

MANUFACTURERS of some forced draft incubators recommend that turkey eggs be removed from the incubator to a separate hatcher at 24 days’ incubation. This change involves a drop in incubation temperature from 99¾ to 97°F., cessation of turning, and a change in position from an angle of 45 degrees from horizontal to a horizontal position in which the eggs lie on their sides. The experiments reported herein were undertaken to determine the effects of transfer to the hatcher and to each of the hatcher conditions at 12, 15, 18, 21, 24, and 25 days’ incubation, respectively. The effects of hatcher temperatures of 93, 95, 97, 98, 99¾ and 102°F. were also determined. Egg length was measured prior to incubation so that its relation to hatchability under the various experimental conditions might be determined. Romanoff (1935) reported experiments in which turkey eggs were incubated for three weeks in a forced draft . . .

INTRODUCTION SOYBEAN meal is widely used as a protein concentrate in the diet of laying fowls. Its value for egg production is not disputed. Hatchability of eggs produced by birds receiving diets containing soybean meal, at least that made from some varieties of soybeans, probably depends on the kinds and amounts of animal protein concentrates included in the same diet. Direct sunlight is a very important factor in the production of hatchable eggs. Byerly, Titus, and Ellis (1933) showed that meal made from the Mammoth Yellow variety of soybeans was inadequate for the production of eggs of high hatchability by semi-confined birds that received an all plant-source diet containing about 20 parts per 100 of the soybean meal. Subsequent studies have shown the Illini variety of soybean to be deficient in the same manner. Nestler, Byerly, Titus, and Ellis (1936) showed that the deficient factor in the diet used was . . .

The rate of growth of the chick embryo depends upon an inherent growth rate, probably identical for all breeds. This rate is modified during incubation in direct proportion to a function of egg size. The increments in wet weight of the embryo are proportional to a function of the weight of the yolk sac, from the time of establishment of the circulation to the time of the changes preparatory to hatching. Both function and proportionality are probably identical for all breeds of chicken, regardless of egg size. The growth in weight of the allantois and the yolk sac have been measured quantitatively for the first time. The weight of the allantois in eggs of different sizes is roughly proportional to the two-thirds power of egg weight after the first three or four days of its growth. During the initial period of its development the relative size is apparently independent of breed, egg size, or embryo weight. The yolk-sac weight in eggs of different sizes is roughly proportional to the circumference of the yolk after a similar initial period of independent growth. Inclusion of the living material in the embryonic membranes in calculations of the rate of physiological processes of the embryo indicates that they are probably of the same order of magnitude throughout the incubation period rather than of sharply decreasing magnitude as supposed by some previous workers.

IT IS a matter of common knowledge that relatively slight variations from the optimum in incubation temperature influence adversely embryonic development and hatchability. Elevation of incubation temperature above normal is more serious than depression below normal but long continued deviations in either direction often lead to poor hatches. It is desirable to know when embryonic death occurs when eggs are incubated at abnormal temperatures and the immediate causes of death, as aids in the diagnosis of the causes of poor hatches. It is also important to know whether embryos in eggs of inherently high hatchability differ in resistance to abnormal temperature from embryos in eggs of inherently low hatchability. Papers by Henderson (1930), Barott (1937), and by Taylor, Gunns, and Moses (1933) contains summaries of the voluminous literature on the effects of abnormal temperatures on early embryonic development. Henderson (1930) measured the growth in weight and nitrogen content of embryos . . .

ConclusionsIt has been found that single fowl pituitaries implanted over the crop glands of 8- to 10-weeks-old pigeons (age computed from time of conception) will, in many instances, cause a prolactin-like reaction. It is assumed that this reaction is caused by prolactin in the pituitaries of the donating fowls.Pituitaries from broody hens cause a greater reaction of the pigeon crop gland than the pituitaries of laying hens. Pituitaries from males cause a reaction about equal to, or slightly less, than the pituitaries from laying hens.It was noted in a few cases that the pituitaries of hens just becoming broody gave a greater reaction than those of hens nearly over their broody period. More data are being gathered on this point.

TURNING eggs has long been known to be necessary in artificial incubation to secure satisfactory hatches. Until the development of Mammoth incubators, however, little attention was given to the manner of turnings eggs or to the number of times they were turned a day. Eycleshymer (1907) appears to be one of the first to report the effect of not turning eggs. He found that he obtained only a 15 percent hatch when the eggs were not turned as compared to 45 and 58 percent hatches when the eggs were turned two and five times per day, respectively. He further states “that position of egg is a factor of little importance.” Jackson (1912) found that eggs turned twice daily hatched slightly better than those moved only once a day and also that “eggs laid flat and turned twice daily gave better results than those kept in any other position.” Comparisons between . . .

IT IS well known that the rate of egg production in the domestic fowl may be stimulated temporarily during seasons of normally short daylight periods by increasing the length of the daylight period with artificial light. Such stimulation is usually followed by a decline in egg production below the normal rate. Payne and Simmons (1934) presented an excellent paper on this subject and reviewed the literature to that date. Whetham (1933) showed that rate of egg production increases during seasons of increasing daylight in widely separated latitudes. Decline in rate of production begins before maximum daylight period is reached, however. The relationship of light to the ovulation cycle in the fowl is less well understood. Atwood (1929) showed that successive eggs in a clutch are usually laid at successively later hours in the day. An egg laid after 2 p.m. under natural day and night conditions is usually followed by . . .

BROODINESS is, to some extent, a detriment to egg production of chickens even with modern methods of management. The influence of environment on chickens has received considerable attention, but mostly from the standpoint of egg production without particular reference to broodiness. The investigations herein reported were made at the National Agricultural Research Center, Beltsville, Maryland, as exploratory tests of the effects of some environmental factors, physical and psychological, on the expression of broodiness by chickens whose previous records had shown that they possessed various degrees of broodiness. The purpose of these investigations was more to obtain an indication, if possible, of the extent to which broodiness, and incidentally egg production, could be influenced by psychological stimuli than to evaluate any specific stimulus or group of stimuli. The authors realize that some of the data are not as complete as could be desired, but feel that the results, such as they . . .

BYERLY, Titus, and Ellis (1933) found that diets consisting of cereal grains, their by-products, alfalfa leaf meal, minerals, and cod liver oil are deficient in some factor, or factors, necessary for the production of eggs of high hatchability. This deficiency is satisfied by range, milk, and certain protein concentrates of animal origin, but not by certain protein concentrates of vegetable origin. Recent investigations by Halpin, Holmes, and Hart (1933) indicate that many diets for laying hens are deficient in vitamin G, and that the hatchability on such diets is low. Their basal diet, composed of yellow corn, oats, wheat bran, wheat middlings, meat scraps, common salt, and cod liver oil, plus scratch feed, grit, and crushed oyster shell, gave a hatchability of only 11 percent whereas the addition of skimmilk or chopped alfalfa hay to the diet raised the hatchability to over 70 percent. In order to determine if vitamin . . .

THE embryonic chick at the time of the laying of the eggs is usually subjected to the most extreme variations in environment it will have to withstand before hatching. In cold weather it may be quickly chilled, and during hot weather it may continue to develop, without pausing, for several hours before being stored under conditions that stop development while being held before incubation. Patterson (1910) found that the embryos show variation in development at the time of laying and Hutt and Pilkey (1930) have pointed out that some embryonic stages may be especially sensitive to external conditions, which may cause abnormal development or death, but would not affect the embryo at other stages. Hays and Nicolaides (1934) considered the variation, in embryonic development of fresh-laid eggs, among hens to be of primary importance, and stated that high hatching hens laid fertile eggs with more fully developed embryos than low . . .

INTRODUCTION DURING the course of an unpublished study to evaluate environmental factors affecting rate of egg production, it was deduced that age at first egg among genetically similar pullets should be closely related to daily hours of illumination. As a corollary, winter hatched pullets should mature earlier than spring hatched pullets. Evaluation of these relationships may enable poultry breeders to correct their genetic selection for early maturity in accordance with date of hatch or persuade them to limit comparisons to groups of pullets hatched during a very limited period. Selection is effective in proportion to the degree with which it reflects genetic variation rather than variation due to environment. Several studies of the effect of date of hatch on age at first eggs are summarized by Lippincott and Card (1939) and Jull (1940). Conclusions as to the effect of date of hatch on age at first egg drawn from these . . .

RECENT papers by Landauer and Landauer (1931) and MacArthur and Baillie (1932) contain data indicating a higher proportion of males than of females among chicks which died during the first few weeks of postnatal life. Landauer and Landauer suggest that the same condition holds for pre-natal mortality. Now it is well known that in man and in some other species in which the male is the heterogametic sex, both prenatal and postnatal mortality among males is relatively greater than among females. Lenz (1923), Huxley (1924), Geiser (1924–25), and others have supposed that recessive sex-linked factors with a deleterious effect on viability account for the relatively greater male mortality. But if species in which the female is heterogametic, as is the case in the domestic fowl, also show greater male mortality, then the hypothesis of harmful sex-linked factors must be abandoned. Landauer and Landauer (1931) and MacArthur and Baillie (1932) . . .

SEASONAL variation in the rate of egg production is associated with seasonal variation in length of day. The excellent paper of Whetham (1933) summarized a very large amount of data from a wide range of latitudes, all showing correlated changes in day length and rate of egg production. Kennard and Chamberlin (1931) showed that seasonal variation can be modified by use of supplementary artificial light, confirming the work of several earlier laboratory workers and of many poultrymen. Kennard and Chamberlin also showed the close relationship of body weight and rate of egg production. A good review of the earlier literature is contained in the paper of Callenbach, Nicholas and Murphy (1944). Several analyses of egg production data for the purpose of describing the relation of time in production and rate of production have been made. Harris et al. (1921) reported that annual production within a genetically similar flock maintained under . . .

APPROXIMATELY 50 percent of the cost of producing and marketing poultry meat consists of feed cost. Consequently, if it were possible to reduce, by any amount, the pounds of feed required to produce a pound of meat, it would increase the profits of the industry. If it were possible to obtain these lower feed costs through breeding it would indeed be worth our efforts. Therefore, a study of the efficiency of feed utilization, on a family basis, becomes an extremely practical as well as an interesting academic problem. Feed efficiency is a very complicated phenomenon affected by many physiological as well as environmental factors. There are at least two definite components, maintenance and growth, which enter into the gross efficiency of feed utilization by broilers. Maintenance requirement probably does not vary greatly per pound of chicken regardless of the weight of the broiler, although such factors as a decrease in . . .

THE genetic aspects of hatchability and the knowledge concerning them have been discussed recently by Jull (1932). It has been established that cross-breeding often increases hatchability and that inbreeding often decreases it. These results of cross-breeding and inbreeding have been attributed chiefly to the different degrees of heterozygosity likely to be produced by these types of matings. Three characters lethal to the embryo when present in homozygous condition have been reported by Dunn (1923), Landauer and Dunn (1930), and Byerly and Jull (1932), respectively. Physical characters of the egg, such as weight, shape, and color, have little relation to hatchability within the normal range of variation of these factors. Evidence presented herein indicates that cross-breeding improves hatchability in inverse proportion to the hatchability of the parental stocks; that further improvement in hatchability is likely to be obtained by mating F1 females to males of an unrelated breed; that genetic factors . . .

EGGS from turkeys whose eggs averaged from 84–89 grams in weight, about the modal egg weight for the material reported, were reported by Marble and Margolf (1936) to have higher hatchability than eggs from females whose eggs averaged less than 84 or more than 89 grams. This finding is in agreement with the concensus of reported work on the effects of egg weight on hatchability of hen’s eggs, as given by Landauer (1937). Data reported in the present paper were collected during the 1937 breeding season at the National Agricultural Research Center, Beltsville, Maryland. The turkey females consisted of 156 birds, chiefly pullets, of several varieties * and crosses * and were mated to unrelated males. All birds were selected for small size, the average weight in January-February being approximately 11 pounds for the young breeding hens and 21 pounds for the young breeding toms. The small size of the breeding . . .

RESISTANCE to disease is a variable factor. Operating together with changes in organism virulence, it is responsible for the severity of any given disease attack. Experimental evidence bringing more light to bear upon the conditions under which pullorum resistance varies may prove a valuable aid to brooding and flock management. Rettger, Kirkpatrick, and Stoneburn showed that pullorum resistance varies with age. Roberts and Card demonstrated the variation of pullorum resistance caused by genetic factors. These authors determined, among other things, that “Selection was effective in producing strains of domestic fowl more resistant than . . . unselected stocks in respect to infection by Salmonella pullora.” The same investigators also noted an increase of resistance under natural conditions in the presence of infection. They reported that among flocks of the Chia Gi variety in the vicinity of Peiping, China, pullorum reactors were present while no evidence of pullorum infection could be . . .

THE ability of the chick embryo to orient itself within the shell prior to hatching time is a subject of dispute. Hutt and Pilkey (1934) stated that if eggs are placed horizontally on a tray on the eighteenth day, and not turned subsequently, all eggs which hatch are pipped on the upper surface. They stated further that eggs turned on the nineteenth and twentieth days are pipped about equally on upper, lower, and intermediate surfaces. They presented no data to support their statements. Waters (1935a) presented data for 225 eggs turned four times daily after the seventeenth day and for 225 controls not turned after the seventeenth day. The turned eggs were pipped about equally on all surfaces, as Hutt and Pilkey stated, but the unturned eggs were also pipped about equally on all surfaces. Byerly and Olsen (1936) reported that about 5 percent of eggs not turned after the . . .

Broodiness was induced in laying fowls of broody races by the injection of prolactin, by Riddle, Bates, and Lahr.1 After prolactin injections laying fowl of non-broody races and males of a broody race became only partially broody, usually clucking without nesting. Burrows and Byerly2 showed that pituitaries from broody fowl have a much greater prolactin content than those from laying fowl and from males, as judged by local pigeon crop-gland response to pituitary implantation.The present work was undertaken to determine the relative potency of fowl pituitaries with respect to genetic constitution of the fowls. White King pigeons of 8-10 weeks conception age were used as recipients for the fowl pituitaries. The local implantation technique of Lyons as described by McQueen-Williams3 was used. The crop-gland responses were recorded as “plus” when any visible stimulation was obtained, “2 plus” when the stimulation was roughly twice the minimal visible response, and so on.Crossbred females were used in their se...

HATCHERYMEN often inquire about the practicability of testing eggs for hatchability prior to incubation. It is often the practice to test eggs for cracks either by tapping them together and by visual examination in daylight or by candling but there is little information as to the value of this practice or as to whether eggs having other defects affecting hatchability might also be tested prior to incubation. Experiments were undertaken at the National Agricultural Research Center, Beltsville, Maryland, to answer this question. Six incubations were run in the months of April to August, inclusive, of lots of eggs one day to one week old tested before the candle or by means of tapping and visual observation in daylight. Seven individuals with various amounts of candling experience examined different lots of eggs. The junior author tested one lot of eggs by tapping and daylight inspection and one lot by candling for . . .