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THE possibility of a relationship between thyroid weight and function has been investigated by several workers. Because the data obtained suggest a positive correlation between weight and function to some observers and a negative correlation to others, the question might be raised whether any relationship exists at all. Data recently obtained in this laboratory, as a result of a study of the effects of environmental temperature on the endocrine glands, may serve to clarify this question. REVIEW OF THE LITERATURE Although Barelli (1932) concluded that, in contrast to that of mammals, the thyroid of birds does not act in heat regulation and Lee and Lee (1937) found that thyroidectomized geese adapted to a cold environment, it is generally accepted that the thyroid plays an important role in regulating the metabolic processes. When the chick is subjected to a cold environment, it responds by increasing oxygen consumption (Kleiber and Dougherty, 1934, . . .

SEVERAL reports have appeared which suggest that thyroprotein, (iodinated casein) may have beneficial effects when fed to young chicks and, during the summer months, to laying hens (Parker, 1943, Irwin, Reineke and Turner, 1943, Turner et al., 1945, Turner, Irwin and Reineke, 1945, Gutteridge and Pratt, 1946, Gutteridge and Novikoff, 1947, Wheeler, Hoffmann and Graham, 1948). No experimental data are available, however, on the effect of feeding thyroprotein during the “growing period,” but Turner (1947) has recommended in a popular article that, “For growing pullets, the . . . (thyroprotein) feeding can continue at the rate of 15–20 grams per hundred pounds of their total feed until the approach of sexual maturity. Then the . . . (thyroprotein) can be cut to 10 grams per hundred pounds of their total feed.” The present paper reports on the effects of feeding thyroprotein during the 12 weeks period (12 to 24 . . .

THE introductory course in poultry husbandry at the University of Georgia is required of all freshman students in the College of Agriculture. It is an intensive course which meets five days a week foreleven weeks (one quarter). Since this is the first and last poultry course that many students will take, it must be primarily a survey of poultry production; and, since most of the students have not had much background in biology, this course must also present sufficient information in poultry biology to give the student an insight into the fowl as a living organism. The objective of this course, then, is to develop some of the most important aspects of poultry culture together with some of the fundamental biological principles which are necessary in order to understand the reasoning behind recommended poultry practices. In the past the traditional approach to this problem has been used. A group of . . .

THREE reports have appeared in recent years which suggested that thyroprotein might be a desirable ingredient for commercial broiler rations. These previous trials were done with small numbers for each dosage level and the chicks were reared in batteries rather than under practical farm conditions. Moreover, the statistical significance of the differences in response to treatment was not determined. Thus a need was apparent for a more extensive test of these findings under commercial production conditions with the attendant crowding, contact with intestinal discharges, and other normal brooding hazards. The work reported here is an attempt to provide further information on the value of thyroprotein when fed to broiler chicks under conditions approximating those in the field. REVIEW OF LITERATURE It is difficult to evaluate the literature on the effects of feeding thyroprotein to growing chicks. Not only have different investigators used different dosages, but the thyroprotein used has varied . . .

EXISTING phenotypic differences among strains or breeds of poultry are thought to be at least partially caused by differences in endocrine activity. While the weight of a gland is not always an accurate criterion of its activity, it is generally conceded that gland weight and function are necessarily associated in the normal bird. This study was instigated in an attempt to determine whether or not breed or strain differences exist with regard to gland size and if such differences can be accounted for by relative body weight. A search of the literature reveals no data on strain differences in weight of the endocrine glands except those presented by Breneman (1941). He reported definite differences between Rhode Island Red and White Leghorn chicks in comb, gonad, and thyroid weights at 30 days of age but the Rhode Island Reds grew very slowly as judged by usual standards. The birds used in . . .

A SEARCH of the literature reveals no specific information on the relationships of feed particle size to water consumption and water elimination as measured by moisture content of the droppings. However, it has been widely observed in the field that the feeding of all-mash diets results in wet, sloppy litter in poultry houses and that the feeding of some grain in the diet materially improves this condition. Hoffmann and Tomhave (1944) and Callenbach (1944) reported that grain and mash feeding of growing chicks resulted in a dryer litter condition than all-mash feeding and Morris (1947) observed that dry litter was associated with the feeding of some grain to laying hens as compared to an all-mash or pelleted diet. In comparisons of pelleted and all-mash diets, Hoffmann and Poitevent (1947) found that the feeding of a pelleted mash to broilers reduced the moisture content of the litter, but Morris (1947) reported . . .

THE phenomenally rapid rate of growth of the White Pekin duck is well known. Reported average weights at nine weeks of age are 4.85 and 5.77 pounds (Horton, 1928; Elford, 1925, 1927) as compared to 2.00 and 2.60 pounds (Hoffmann, 1946; Klein, 1949) for relatively rapid growing chickens. The marked difference in growth rate between the species is also reflected in the maximum size attained. A White Pekin drake attained the remarkable weight of 10.5 pounds at 68 days of age (Hunter and Scholes, 1943), as compared to a New Hampshire cockerel that weighed 5.12 pounds at 77 days (Jull, 1949). Recent work with chickens has established a relationship between rate of growth and thyroxine secretion. Fast growing strains have an inherently higher thyroxine secretion rate than slower growing strains (Glazener and Shaffner, 1949). The question naturally arises whether differences in growth rate between species can also be partially accounted . . .

IN THE spring of 1947 a few and in 1948 a considerable number of “sports” appeared in the Broad Breasted Bronze flock of Mr. Robert K. Shearer, a Pennsylvania turkey breeder. Because these aberrant individuals were markedly smaller in body size than their contemporary normal-colored Bronze turkeys, this matter was referred to one of us (C.E.K.) whose interest in possible correlations between simply inherited mutant coat colors and morphology, physiology and behavior as factors in preadaption to domestication is well known. In the fall of 1948 a trio each of mutants and “normal” colored Bronze were kindly furnished to the University of Georgia by Mr. Shearer. When circumstances made it impossible to obtain poults from these birds, Mr. Shearer, during the spring of 1949, made weekly shipments of day-old poults. Unfortunately, the already poor viability of the mutants is reduced by shipping so that it seems doubtful that sufficient adults . . .

Length of day is a major factor controlling egg production of birds. That egg production can be initiated and/or stimulated in the domestic fowl, duck or turkey by increased exposure to light is too well known to require documentation. Sexually dormant adult birds of these species begin to lay about two weeks after the regimen of increased light is initiated. A further observation of interest, although admittedly not particularly to the point, is the precocious sexual development of immature 10 to 12 week-old broiler pullets in late March and April. Numerous follicles of ovulatory size are commonly seen in broilers processed at Gainesville, Ga. The consistent occurrence of this phenomenon in the springtime during the period of increasing day-length suggests that this too is a response to light. Response to increased exposure to light has also been produced in wild birds such as the starling (Bissonnette, 1933; although in this . . .

The generally-accepted recommendation of 3½ square feet of floor space per bird for White Leghorns and 4 square feet of floor space per bird for the heavy breeds seems to have developed from the practical experience of poultrymen. Experimental evidence on this subject has been lacking except for the report of Kimber (1941) who found that, over a 22-week period, White Leghorns allowed 4 square feet per bird laid at a rate of 70.8 percent as compared to 62.0 percent for birds allowed 3.5 square feet, 61.9 percent for birds allowed 3.0 square feet, and 61.4 percent for birds allowed 2.5 square feet of floor space per bird. In this experiment the area per bird was kept constant by adding additional birds as the original birds died, but these additional birds were not included in computing egg production. In another experiment Kimber did not add additional birds, but permitted the . . .

The American Standard of Perfection specifies standard weights for the various breeds, but it is widely recognized that both show and utility specimens often fail to reach these weights. While anyone consulting the “standard” will find the ideal weights for a breed, they fail to gain a true concept of the average size of the breed as it is commonly found in the field. Moreover, poultry textbooks quote the “standard” weights as an indication of the size of breeds and thus give the student a false idea of their true size. For instance, the “standard” indicates that the Barred Rock hen is one pound heavier than the Rhode Island Red hen, although it is difficult to recognize any difference in size between the two breeds as found on commercial poultry farms. Data on R.O.P. candidates for the trap-nest year 43–44 have been published-by Godfrey (1946). These data show a . . .

Low fertility and low hatchability are common faults of certain strains of Broad Breasted Bronze turkeys. The ultimate solution of this problem probably depends on additional emphasis on hatchability as part of a long-term breeding program. There is need however, for an interim solution of the problem. The following evidence indicates that crossbreeding may be a suitable technique for the immediate improvement of fertility and hatchability. Byerly, Knox, and Jull (1934), concluded that crossbreeding in chickens is likely to increase hatchability if breeds of low hatchability are crossed but not if the parental stock averaged above 80 percent in hatchability. Clark, Runnels, and Livesay (1944), reported a singificant increase in hatchability but not infertility when reciprocal crosses were made between Broad Breasted Bronze and Bronze, Bourbon Red, and Black varieties of turkeys. There was evidence, however, that matings of B.B. Bronze toms with hens of the medium sized varieties resulted . . .

Recent unpublished reports from the military forces and from entomological workers, Annand, et al. (1944) concerning the use of DDT (dichloro-diphenyl-trichloroethane) as an insecticide, suggested several possible uses for this new product on poultry farms. Production of this material has already been so expanded that within a year large quantities should be available for civilian use. The compound DDT was first synthesized by Zeidler (1874) but attracted little attention until recently when entomological investigations revealed it to be a highly effective insecticide. Chemically, it is a crystalline white solid, practically odorless and tasteless; insoluble in water, but soluble in most organic solvents; stable on exposure to air and sunlight. Recent work by the U. S. Public Health Service, Lillie and Smith (1944), and Smith and Stohlman (1944), shows that DDT is toxic to rabbits, guinea pigs, and rats. Lindquist, et al. (1944) gave rabbits 228 to 400 milligrams DDT per . . .

It has been shown that goiters could be produced in chicks by feeding inorganic iodide to the hen (Wheeler and Hoffmann 1949a). This was not unexpected because it had previously been shown that goiters could be produced in chicks by injecting KI into 16-day old embryonated eggs (Wheeler and Hoffmann, 1949b). These findings suggested that inorganic iodide present in synthetic thyroprotein (STP) might cause the goiters found in chicks from hens fed STP. The goiters produced by either inorganic iodide or STP were comparable in weight and histologically indistinguishable (Wheeler and Hoffmann, 1948) and it was known that STP contains 1.5–2.0 percent inorganic iodide (Graham 1948). Thus it appeared likely that inorganic iodide might be the goiterogenic substance in thyroprotein. To test this hypothesis, an iodide-free sample of synthetic thyroprotein was obtained from Dr. W. R. Graham, Jr. of Cerophyll Laboratories, Kansas City, Missouri. Four groups of ten hens were . . .