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Dwarf (dw) chicks were significantly heavier at hatching and had significantly more unabsorbed yolk material than nondwarf chicks of the same sex from the same sized eggs. Body weight minus yolk did not differ between the two groups within sex. In a separate trial where no adjustments for egg weight differences or sex were made, hatching weight of dwarf and normal chicks did not differ, but body weight minus yolk was significantly reduced in dwarfs. As a result of these differences, residual yolk sac weight was again significantly larger in dwarfs. No significant difference in leg length between dwarf and normal chicks at hatching was observed. The regressions of body weight at 2, 4, 6, 8, 10 and 12 weeks of age on weight of the egg from which the chick hatched were highly significant for females in a dwarf broiler-type population. In contrast, the regressions were significant only through six weeks of age in males. Phenotypic correlations between body weight and egg weight exhibited a similar pattern. No significant quadratic regressions were observed between these two variables.

VARIATION in weight of tissues which respond to hormone stimulation may arise from: (1) variation prior to hormone stimulation, (2) variation in amount of hormone to which the tissue is exposed, and (3) variation in sensitivity of tissues of different individuals. Both initial variation and that due to hormone stimulation are affected by genetical and environmental differences between individuals. This report is concerned with early identification of genetic effects on the weight responses of the testes and the comb. These may, or may not, characterize the responses expected from each chicken throughout its life span. The small amounts of androgen or gonadotrophin which may be present in the blood stream prior to 11 days after hatching would appear to be below the threshold for stimulation of comb and testis size in large bodied breeds. Although Breneman (1941) obtained evidence of gonadotropic and androgenic effects on the testes and combs of …

SINCE the advent of the broiler industry more than 20 years ago, poultry breeders have been selecting for rapid growth rate in broiler-strain chickens. They have made much progress. However, it has been difficult to separate genetic progress from that resulting from advances in nutrition for improvement of growth rate. Jaap, Smith and Goodman (1962) used a randombred control population to measure the genetic change which occurred in eight-week body weight of broilers produced commercially between 1955 and 1959. During this period the breeders were estimated to have increased the eight-week weight of broilers by approximately ½ lb. This ½ lb. was almost a 20 percent gain achieved in four generations. Naturally, poultry breeders are wondering whether they may be approaching the upper limits for rapid creases in growth rate in present day populations. The implications of genetical theory (Lerner, 1958; Falconer, 1960) are not clear. Therefore, several additionals election…

REGARDLESS of agitation for the sale of dissected carcasses, the conformation of market poultry primarily determines its monetary value for human consumption. Broad-breasted and plump dressed birds are preferred to those having narrower breasts. Experiments demonstrate that this difference is not solely a question of fat deposition. Even superficial observation of existing strains proves that apparent plumpness of the body is largely heritable. The observations recorded in this report indicate methods of recording, summarizing, and comparing differences in body conformation of live and dressed poultry. The two species used are the domestic chicken and turkey. These represent the majority of the poultry marketed for human consumption. CRITERIA OF CONFORMATION In describing the conformation of dressed birds all linear measurements must be related to the volume of the body. Since differences in specific gravity of birds are negligible, body weight is considered to be the most practical measure of volume. To . . .

THE I-gene, an inhibitor of black (melanin) color, is currently being used in the development of the popular “dominant white” crossbreds for broiler production. Since none of the competitive meat strains posessed this gene, poultry breeders have introduced it into sire lines by crossbreeding. In a program of transferring I into the Barred Plymouth Rock by a series of back-crosses, it was observed that the Barred backcross segregates lacking the I-gene grew more rapidly than their white sibs. Several genetic mechanisms could give rise to such a suppression of body growth rate: 1 The I-gene interacting with some of the genes present in the Barred Plymouth Rock. 2 Two alleles at the I locus, both suppressing black color but only one suppressing growth rate. 3 The I-gene being linked with a major growth suppressing gene. 4 The I-gene per se having a deleterious pleiotrophic effect on body growth. Willier and …

SCIENTIFIC literature contains many reports on weights of glands and tissues of young chickens. Due to large variations of both genetical and environmental origin in the data reported, it has been impossible to establish any weight standards for specific tissues at specific ages of the chicken. This report attempts to provide such standards for early growth periods of a population readily available to research workers. The population was developed at Cornell University (King, Carson and Doolittle, 1959) and is being maintained as a base population for the Regional Poultry Breeding Project of the North Central States. Since 1959, the Ohio population of the randombred stock has been reproduced from 40 paired matings according to the design proposed by Gowe, Robertson and Latter (1959) for maintenance of Randombred Controls with a minimum of genetic change. MATERIALS AND METHODS Since age of dam has been proven to affect the relative weight of…

(1964). Poultry Science in the Common Science Market. World's Poultry Science Journal: Vol. 20, No. 3, pp. 166-174.

A DIVERSITY of body outlines as depicted by the feather contour exists in breeds and varieties of domestic fowl. Poultry husbandmen have generally considered that these plumage outlines reflect the underlying body contours of the bird. Visually, breeds differ in abundance of feathers (for example, Cochin) as well as the closeness with which they lie against the body surface (for example, Cornish). Breeds of chickens are classified according to these plumage outlines which are based upon artists’ and photographic ideals. During recent years considerable importance has been placed upon body shape of fowl when prepared for the table. This emphasis has been accentuated by the increasing practice of selling at a higher price per pound those dressed birds which possess qualities desired by the consumer. The classification and tentative specifications for United States standards and grades, for dressed chickens (1938) describe the characteristics commonly considered to supply evidence of table . . .

WHITE feathers in the plumage of Rouen and Gray Call ducks are objectionable from the exhibition point of view. This is especially true when these feathers occur in the neck of the female, or in the main wing feathers of either sex. Ducks showing white in these regions are disqualified under terms of the American Standard of Perfection. The Blue Swedish breed, however, as outlined by the Standard, has a large white bib and two white primary wing feathers on each side. A series of experiments was undertaken, using ducks of the Mallard plumage pattern, to analyse the inheritance of white spotting. The Blue Swedish breed has recently been used to study the relation of their white spotting to that occurring in mallard-colored ducks but the data are as yet meagre and are not included in this report. As stated above, all the ducks used had the color pattern of . . .

MANY females produced from crosses of barred columbian, (B S e), males and red, e, females develop a greenish shank coloration by the broiler age of 8 to 12 weeks after hatching. This greenish shank coloration, often designated as “willow,” may vary in incidence from 12 to 80% of the females at the broiler age. It is observed much less frequently in males. Apparently the greenish tone is due to melanic (black) pigment being deposited in the lower layers of the skin and scales. A similar greenish shank coloration is known to be produced by the wild type allele (id+) of the gene which inhibits dermal melanin production in the shanks. For a review of the effect of the Id gene the reader is referred to Hutt (1949). That the id+ is not involved in the results reported here is indicated from the following data. Sixteen Barred Plymouth Rock males …

MANY processors and breeders believe that certain strains and crosses differ in yield of eviscerated (ready-to-cook) poultry. Should such differences exist, it becomes important to determine the breeding methods by which meat yields may be increased. Limited data for broilers and fryers have been given in reports by Jull and Maw (1923); Vernon (1923); Lowe (1941); Jull, Phillips and Williams (1943) and probably others. Dressed yield in these reports varied from 85 to 90 percent of the live weight, and evisceration yields varied from 67 to 75 percent. Much of the differences between observers may be due to differences in methods of processing the chickens. The larger percentage yields given in these reports were usually for the larger birds. Several reports are available on the weights of body parts and percentage yields in terms of edible meat. In addition to those cited previously, Mitchell, Card and Hamilton (1926 Mitchell, Card and Hamilton (1931) have . . .

THE Blue Andalusian never breeds true to color. The offspring of blue parents are approximately one-fourth black, one-half blue, and one-fourth white with gray flecks. This phenomenon is well known to poultry raisers and students of heredity. As a result there have been many popular statements that blue plumage in chickens, ducks, and turkeys is produced by crossing black with white. In ducks and turkeys, as well as most chickens, blue-gray progeny usually do not arise from such crosses. The purpose of this article is to present some records which aid in explaining the inheritance of gray (blue, slate) plumage and its interaction with other color patterns. Scientific reports on the inheritance of blue plumage color in ducks and turkeys are few and not in definite agreement. In turkeys, Robertson (1929) and Taibel (1933) report blue as an autosomal dominant. Using slate “sports” from a Bronze flock, Asmundson (1940) found . . .

WHAT is the color genotype of the Delaware breed? The answer, as best deduced from research reports and textbooks, seems to be “C C i i Al(Al) S(S) B(B) e e bl bl Mo Mo bg bg La La pg pg Sg Sg A A Pi Pi Pk Pk Rs Rs sd sd sp sp — — — — — etc.” But is this satisfactory? Have we any hope that the vague ending will ever be completed? And is such complexity necessary? For 30 years or more Drosophila geneticists have had a solution for such difficulties, yet none of the poultry geneticists such as Hutt (1949), Jull (1952), or Cock (1953) has used it. That solution was to specify in a genotype only the differences from a standard, namely the wild type. In this way, genotypes can be complete but brief. Using the red jungle fowl for our color standard, we may answer…

THE poultry industry is based upon two fundamental biological principles; namely, growth and reproduction. In chickens, the egg production phase of reproduction has major economic importance with growth taking second place. With turkeys, ducks and geese, however, growth takes first place in importance and differences in the egg and reproduction are secondary in economic returns. For these reasons all classwork which deals with poultry production must emphasize the biology of the bird and the way it reacts to such environmental factors as feeding, management and housing. To a limited extent, biological reactions may be classified by rules of good husbandry without specifying how these rules satisfy the innate peculiarities of the bird. Another approach is to study the specific effect of the husbandry practice on the known, or postulated, physical and physiological interactions which characterize the living organism. It is probable that both methods may be so integrated as to . . .

This report explores the effects of dw on early growth rate as well as adult body size in populations produced during the transfer of dw from an egg-type (Leghorn) to broiler-type populations. This sex-linked gene, dw, was observed to have the following effects when compared with those of its normal, dw+, allele: Eight week body weight of heterozygous, dw+dw, sons from normal, dw+, dams was equal to that of their normal homozygous, dw+dw+ sons. In contrast, eight-week body weight of dw+dw sons from dwarf dams may have been slightly suppressed when compared with dw+dw+ sons of normal dams. In the hemizygous females, the smaller egg size from the dw dam reduced the eight week weight of her dwarf (dw) but not her normal (dw+) daughters. As the amount of broiler-type inheritance was increased through backcrossing to transfer dw from the egg-type to broiler-type populations, the depressing effect on dw on growth of females was reduced from 37.1 to 19.2% at eight weeks of age and from 29.4 to 19.8% at 26 weeks after hatching. The effect of dw on adult size, as estimated by shank length, did not appear to diminish after the first back-cross to broiler-type dams.

(1969). Large Broilers from Smaller Hens. World's Poultry Science Journal: Vol. 25, No. 2, pp. 140-143.

THE weight response of the baby chick’s comb to androgenic stimulation from testosterone and gonadotrophin injection has been changed by selection (Jaap, 1962; Nestor, 1964; and Nestor and Jaap, 1965). This report is concerned with the question of whether these genetic changes in hormone response during the first ten days after hatching persist into the pullet laying period. Also, whether changes in the response of cells in the baby chick’s comb are accompanied by changes in the response of other tissues of the bird’s body and whether these responses are age specific or persist throughout life. Should genetic capabilities be established early in life, it would be possible to predict future productive and reproductive performance soon after hatching of the chick. MATERIALS AND METHODS Details of the origin and maintenance of the populations used in the study were given by Nestor (1964) and Nestor and Jaap (1965). One population designated …

BLACK (melanic) pigment is frequently observed when the skin is removed from the abdomen of broiler chickens. This pigment is located in the fascia closely adhering to the external abdominal muscles. Intensity of color varies from pale gray to jet black. The size of the pigmented area may be very small, a spot on the navel or a streak on the median muscle raphae. More often it is large, covering the posterior half of the two external abdominal muscles. In ready-to-cook poultry this objectionable coloration is often hidden by the overlying skin. Frequently the blackness is exposed by the cut in the abdomen through which the viscera have been removed. Sometimes it is necessary to cut away part of the abdominal wall to remove the black, muddy or dirty appearance produced by this melanic pigment in ready-to-cook broilers. This black abdominal pigment is deposited by migratory melanocytes similar to those . . .

NUMEROUS heritability estimates for egg production and egg quality traits are available in the literature. Most of these reports were calculated from matings of dams within sires and, therefore, include a part of the non-additive variance which may have been present in the population. Relatively few researchers have attempted to partition the additive and non-additive genetic variance for these traits. Jerome, Henderson and King (1956) reported that the magnitude of non-additive genetic variance was larger than the additive genetic variance for survivors’ production over a period of a year. Also, the authors reported that the magnitude of non-additive variance was larger for production for 365 days as compared with shorter production periods up to four months. Fuchs and Krueger (1957) reported that non-additive effects appeared to be important in egg production in single and three-way crosses but of questionable magnitude in pure strains. According to Jerome, King and Henderson (1956),…

THE deposition of fat in the chicken’s body is extremely slow during the period of most rapid growth. As rapidity of growth subsides a gradual increase in the rate of fat storage takes place. After sexual maturity is reached in either sex this fattening process is slowed down or ceases entirely. In strains which are slow to mature sexually, or when sexual maturity is eliminated entirely by caponizing, the fattening process proceeds for a much longer period of time. During this prolonged fattening period the chicken approaches a fully fattened condition. Early sexual maturity in the male prevents fattening during the last 12 to 14 weeks of the growth period. This is due primarily to the increased activity characteristic of the mature cockerel. In contrast the pullet stores increasing amounts of fat during the period just prior to and immediately following sexual maturity. Halnan and Cruikshank (1933) have shown that . . .

RESISTANCE to breakage and improvement in hatchability are two economically important attributes of eggs. Both have been demonstrated to be heritable (Quinn, Gordon and Godfrey, 1945; Gowell, 1903; and others); therefore the question arises: “Are breaking of eggs and hatchability testing the simplest and most expedient methods for use in selecting candidates for the breeding pens?” Several devices have been proposed for testing breaking strength (Romanoff, 1929; Morgan, 1932, Almquist and Burmester, 1934; Lund, Heiman and Wilhelm, 1938; and Kennard, 1944); and shell thickness has been measured by a number of workers (Hays and Sumbardo, 1926–27; Lund, Heiman and Wilhelm, 1938; Berg, 1945). Both of these methods used for identifying differences in shell quality are tedious and costly, and greatly reduce the value of the broken egg. Visual differences in shell texture are subjective and have not proven to be very accurate (Funk, 1934; Henderson, 1942) whether considered from the . . .

(1952). New Theories on Methods of Selection and Mating in Poultry. World's Poultry Science Journal: Vol. 8, No. 2, pp. 114-127.

THE analysis herein reported is concerned with the possibility of securing linear measurements for comparing body shape of live birds. At present selection of breeding stock in both turkeys and market chickens is accomplished purely by subjective comparison. Numerical expressions of body shape lend themselves to accurate analysis. By their use progress in breeding market birds may be evaluated. Jeffreys (1932, 1936) has reported measurements which he considers ideal for the White Holland turkey. However, these measurements are for turkeys at eight months of age, i.e., older than turkeys are ordinarily dressed for market. Jull (1935) in his outline of the turkey breeding plans at Beltsville gives a popular description of a desired market turkey; namely, “ . . . the ultimate object being to produce a relatively short-legged, long-bodied, early maturing, good-fleshing type. . . .” The purpose of this study is to determine whether it is possible to . . .

THE function of the bursa of Fabricius, a lymphoendothelial gland of birds, is rather obscure. Glick (1956) emphasizedthe rapid growth of the bursa of Fabricius during the first few weeks after hatching of the chicken. During the past few years, a number of research reports have demonstrated that it is involved in the production of some antibodies in the chicken (Chang, Rheins and Winter, 1957, Rheins and Winter, 1959; Glick, Chang and Jaap, 1956; Glick, 1956, 1960; and Mueller, Wolfe and Meyer, 1960). The involvement of this gland in the stress complex is indicated by the reports of Perek and Eilat (1959, 1960); and Newcomer and Conally (1960). Since the bursa begins to atrophy as early as six weeks after hatching in the Leghorn chicken, its physiologica l function can be of importance only during the first few weeks of its life. The role of this gland in the physiology of the young…

OWING to the economic importance of the egg-laying characteristic of the fowl much research has been published on the inheritance of those phenomena associated with reproduction and sexual development. However, comparatively little is known concerning the physiological processes involved in development and activity of the reproductive organs. A knowledge of these processes is essential to a thorough genetical study of the reproductive phenomena in birds. The researches reported were planned in order to obtain a method by which the bases of individual differences in gonadal function might be evaluated. It has been shown by previous workers (Allen, 1932, p. 778) that the pituitary body is chiefly responsible for the development of the immature gonad of the chicken and duckling. Jaap (1934) found that the testes of adult Mallard drakes may be caused to increase in size during the winter months by feeding desiccated thyroid. This increase is due presumably to . . .

FROM a broiler production standpoint it is important that breeds and varieties of chickens grow and feather rapidly during the first two or three months of their life. Since it is only the hereditary differences which make possible any improvement in the varieties, it is important to know the extent to which differences in early growth and feathering are caused by environmental factors and how much they are caused by heredity. The present study was undertaken to measure the relative importance of some of the chief causes of variation when the chickens are fed and managed in the same manner during the same year. SOURCE OF DATA The records analyzed in this report were obtained during the early part of the 1936 brooding season. They consist of weight and feathering records of pedigreed eight-week-old chickens from six standard varieties and similar records from a crossbreeding experiment. Since these chickens were . . .

THE performance of his topcross progeny should give the best estimate of the breeding worth of an inbred male used for this purpose. Since inbreeding increases homozygosity, the value of topcrossing might be increased by mating the best cross-progeny tested males with their sisters. No previous tests using cross-progeny tested sires for inbreeding in poultry have been found in the literature. In an attempt to increase egg production, Hays (1935), Waters (1938), Maw (1942), Knox (1946), and Dudley and Pease (1948) topcrossed inbred males on randombred females of the same breed and variety as the males. This was done despite the established fact that heterosis in plants usually is increased by crossing diverse genetic materials. Most of these experiments resulted in no significant increase in egg production of topcross progeny over randombred progeny kept as controls. Topcrossing of inbred males of one breed on randombred females of another breed was …

POPULARITY OF WHITE PLYMOUTH ROCKS IN OKLAHOMA APPROXIMATELY 27 percent of all birds banded in the flocks of 78 Oklahoma Poultry Improvement Association hatcheries are White Plymouth Rocks. This estimate is based on the data from 2,042 flocks containing 316,933 birds as included in the 1942 Yearbook of the Oklahoma Poultry Improvement Association. Since these hatcheries are scattered over the state, the figures in Table 1 probably represent the nearest estimate of the distribution of varieties in Oklahoma. Estimating from the same source, there appear to be approximately twice as many flocks of White Plymouth Rocks as flocks of any other variety. Due to the prevalence of the White Plymouth Rock, any strain differences which return an economic advantage could be utilized to a greater extent than in any other variety raised in Oklahoma. This paper reports a study of the action of five gene pairs which, in certain combinations, . . .

Before the physiology of sexual dimorphism in birds can be completely understood the normal change from the male winter plumage to the female-like summer plumage in the Mallard drake must be explained. This report embodies certain facts regarding feather pigmentation and growth rate in Mallard drakes which must be considered in future studies of the physiological basis for this “eclipse” or “summer plumage” change of the adult male duck.The males used in these experiments are semi-domesticated Mallards, the majority of which are genetically “dark-phase mallard” (M Li).1 These drakes are very uniform in breeding, and in adult body weight, between 980 and 1160 gm. The males are left in outside yards until they are to be used in an experiment, when they are brought indoors and kept in artificially heated and lighted pens, the hours of illumination being approximately the same in all trials. At the beginning of the experiment, 50 to 60 feathers are plucked from the middle of the ventral surface on either side...

TWO glands, the spleen and the bursa of Fabricius, are known to exert a major control over antibody formation in the young chicken. The involvement of the spleen has been known for some time (Wolfe et al., 1950). The bursa of Fabricius has been known to grow very rapidly in the young chicken. Glick (1956) has confirmed this rapid early growth and shown that it begins to atrophy as early as 6 to 10 weeks of age. Herran (1955) bursectomized male chickens at one month of age and observed that, during the next 90 days, their body growth exceeded that of the controls. Chang, Glick and Winter (1955) first reported that bursectomized chickens failed to produce antibodies against Salmonella typhimurium. These experiments were described in more detail by Glick, Chang and Jaap (1956). Chang, Rheins and Winter (1957) have demonstrated the importance of the bursa of Fabricius during the first …

AUTO-SEX linkage is a name given to the phenomenon of simple and positive sex differences apparent among baby chicks of a fixed breed, not crossbreds. Perfect sex separation without the necessity of resorting to crossbreeding should have many beneficial uses in the present organization of the baby chick industry. For maximum use and value this method of identifying the sexes must be evident to everyone engaged in poultry production. Distinct sex differences would allow merchandizing of chicks on a male and female basis, eliminating all chance of error. Positive sex separation of live chicks at hatching has many advantages for the research worker. A rapid and perfect method of sex identification would expedite studies of sex differences in physiology, nutritional requirements and efficiency, and experimental sex reversal. HISTORICAL There are three methods by which sex separation of baby chicks has been attempted. First, inter- and intra-breed crosses involving differences in . . .

THE females which produce chicks for broiler production have changed greatly during the past 15 to 20 years. Broiler chickens were twice as large at 8 weeks of age in 1965 as those of the same age in 1952 (Maine Broiler Test Reports, 1952–1965). The mothers of broiler chicks now reach an adult body weight of 3 1/2 to 4 kilograms. During this same period (1950–1965), egg-type females have been reduced from about 2.2 kilograms adult body weight to approximately 1.9 kilograms. This dramatic difference in body size between broiler- and egg-type females has been accompanied by many other changes in appearance and behavioral activity. External and behavioral differences are more readily observable than those which are internal and physiological The following report records observations concerning non-rhythmic laying patterns and the high incidence of egg defects in these large-bodied broiler strains. Irregularities of oviposition time and the accompanying defects appear . . .

ACCURACY in estimating heritabilities may be improved by increasing the number of parents, by choosing the most appropriate mating system, and by increasing the number of progeny. Goodman and Jaap (1960) concluded that, within closed populations, heritability estimates from 50 sets of diallel matings consisting of 200 families with the equivalent of four full sibs per family, were superior to estimates from 30 triallel sets consisting of 270 families with full-sib families of two individuals. The two strains of New Hampshire used in that report had long closed-flock histories and the additive genetic effects on eight-week weight were low compared with reports in the literature. Non-additive genetic effects were very low or non-existent. Also, the parents used in that study had been intensely selected for growth. Weights of the spleen and the bursa of Fabricius in baby chicks from a randombred population were chosen for the tests to be reported …

THE Cornish Bantam has possibilities of being suitable for economical market poultry production. Standard weights (American Poultry Association, 1938) for males and females under one year of age are 30 and 24 ounces, respectively. At the present time only a few of the smallest Dark Cornish Bantams approach these standard weights. By four months after hatching the majority of the cockerels reach two pounds live body weight and the pullets about 1½. pounds. At these sizes the body is much plumper and better proportioned than that of the common breeds. Assuming that changes in the proportions of fat and muscle to bone occur at approximately the same ages, the Cornish Bantam should have a higher percentage of flesh and fat at the 1½ to 2-pound sizes than larger-bodied breeds at the same size. This resultant dressed carcass, then, would have a better market finish and be worth a higher price . . .

The sex-linked gene, dw, greatly reduces the rate of egg production in egg-type hens (Hutt, 1959) but does not reduce the rate of lay in broiler-type dams (Prod’homme and Merat, 1969). The question arose whether a 30 percent body size reduction attributable to dw might partially alleviate the defective egg production syndrome (Jaap and Muir, 1968) of the broiler dam. Jaap and Clancy (1968) have demonstrated that broiler pullets laying at a rate of 56 percent have more ovarian follicles in rapid growth stages than Leghorns laying at an 84 percent rate. Since dw reduces growth (protein anabolism) rate, might this gene also reduce the rate of yolk (lipoprotein) deposition in the follicles of the ovary? van Tienhoven et al. (1966) have suggested that dw may act to reduce the amount of growth hormone in the circulation of the dwarf female. Insufficient growth hormone could limit the rate of yolk…

(1965). Minimum Population Size and Source of Stock for Gene Pools. World's Poultry Science Journal: Vol. 21, No. 2, pp. 172-174.

The fat content of the body of female chickens increases rapidly at the onset of lay (Halnan and Cruickshank, 1933). The researches of Zondek and Max (1939), Lorenz (1938 and 1943) and Flock and Bollman (1942) demonstrate that this rapid fattening may be artificially induced by subcutaneous injection and implantation of estrogens in male chickens. Many investigators have shown that diethylstilbestrol has a strong estrogenic potency when administered by mouth in mammals. No reports of feeding estrogens to chickens have been found in the literature. Practical usage of estrogens in fattening broiler chickens would be greatly expedited if an inexpensive form could be found which would be effective when mixed in the feed. The tests for oral estrogenic potency used in this study (Table 1) are the increase in oviduct weight, the decrease in comb weight of males and the feather form in the saddle region. Daily administration of 0.5mg. . . .

Glick (1955) observed that the weight of the bursa Fabricius at two weeks of age in White Leghorns (0.44 gm.) was larger (p In baby chicks of a randombred broiler-type strain, 72 to 92 percent of the variance in weight of the bursa of Fabricius at a constant body weight was attributable to genetic effects (Jaap, 1958). Since Chang, Rheins and Winter (1957) had demonstrated the importance of the bursa in antibody production, it appeared desirable to explore whether breed differences in bursa size existed at hatching. MATERIALS AND . . .

In the course of experiments designed to test the effects of embryonic sexual modification on postnatal growth of turkeys (Jaap, Ingram and Godfrey, 1951) a method by which fertility of turkeys eggs could be detected from 22 to 30 hours of incubation was utilized. While the idea is not new, it is thought that this particular method for the early detection of fertility in turkey eggs may be of value to other workers. King (1936) reported that fertility in chicken eggs could be detected at 15 hours of incubation by the use of a specially Constructed egg candler. Olsen and Knox (1938) stated that fertility in chicken eggs could be detected at 16 to 20 hours of incubation. The former worker used a 500 watt bulb, while Olsen and Knox used a 75 watt clear glass electric bulb. Both used filters of various kinds. Marsden and Martin (1946) suggested that . . .

Small 1.1 kg. egg-type pullets having the sex-linked dw dwarfing gene were more resistant to a force molting program started at 11 months of age than were their 1.4 kg. non-dwarf counterparts. Water deprivation appeared to prevent egg production sooner in the dwarfs than in the non-dwarfs but egg production eight weeks after initiation of the force molt program was 46 per cent versus 64 per cent for the non-dwarf pullets.

During the senior author’s tenure of a Fulbright Research Scholarship, Doctor Greenwood had available at the Poultry Research Centre several inbred lines of Brown Leghorns (Greenwood and Btyth, 1951; Blyth, 1952). These lines appeared desirable for detecting differences in hormone production and response as well as the relation of the endocrine system to the expression of hybrid vigor in growth rate and egg production. This report is concerned with the variability in response of the baby chick’s comb to testosterone propionate. the androgenic comb response Fussganger (1934) emphasized the small differences in androgenic potency which could be measured by external application of the hormone to the comb of the capon. Ruzicka (1935) was probably the first to suggest that the baby chick comb response be used as an assay for androgens. Since that time there have been many research reports concerned with the possibility of the chick-comb response as a sensitive assay for androgenic potency of unknown solutions....

Gowe, Robertson and Latter (1959) described the use of paired matings for maintenance of control strains with a minimum of inbreeding. This system has been adapted for both controls and selection in populations composed of 40 pairs of parents. The system consists of mating pairs of selected parents at random with one exception; namely, avoidance of full sib matings. Matings are made by artificial insemination from pairs retained in individual cages. Forty males and 40 females have been used for reproduction of each strain. Reproduction is begun when egg production of the females reaches approximately 50 percent. Between 400 and 500 chicks are hatched from each 40 pairs of parents. With the exception of a few strains having very poor reproductive rates, this has been accomplished by two hatches two weeks apart. RANDOMBRED CONTROL STRAINS For reproduction of the randombred controls, 2 sons and 2 daughters from each pair of…

SAMPLE SIZE AT EIGHT WEEKS UNPUBLISHED data for many thousand chickens demonstrate that the variance for body weight at eight weeks of age seldom exceeds 0.10 for males and 0.07 for females of most broiler strains and crosses. A body weight estimate less than 0.1 lb. from the true average weight was desired in samples from pens in which the number of chickens exceeded 200 birds. A truly random sample with these specifications (probability of 0.01) should be obtainable from approximately 70 cockerels, 50 pullets, or 90 non-sexed chickens. This number is adequate for flocks of any size containing more than 200 growing chickens. Samples of approximately 25 birds from each of three locations have proven most useful to obtain a randon sample from large pens. THE SAMPLING METHOD A three-section, low (2½ ft.), hinged catching frame is carried into the pen in a folded condition. The catching frame is …