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KEMPSTER and Turner (1945) and Andrews and Schnetzler (1946) reported on the effect of thiouracil on the growth and fattening of broilers. Parker (1943), Irwin, Reineke, and Turner (1943) and Turner, Irwin, and Reineke (1944) reported on the effect of thyroactive iodocasein on the growth and feathering of chicks. These reports suggested that a further effect of these substances in the diets of chickens might be assayed, namely, their effect on resistance to parasitism. It appeared useful to determine whether a mild hypothyroid condition and increased fat deposition, or a mild hyperthyroid condition with increased growth rate, might enable the broilers to overcome weight losses due to the establishment and maintenance of parasitic infections. MATERIALS AND METHODS Chicks used in the first 3 experiments were straight-run New Hampshires obtained from commercial hatcheries in Knoxville, Tennessee; New Hampshire chicks were supplied by the Department of Poultry Husbandry of the Kentucky Agricultural . . .

PARKER (1943) fed graded amounts of thyroactive iodocasein to five lots of Rhode Island Red chicks during a period of 12 weeks. At the optimum level a slightly greater rate of growth was observed in comparison to the controls and a rather marked stimulation of feather growth. Irwin, Reineke and Turner (1943) confirmed these results using White Plymouth Rock chicks. The effect of thyroactive iodocasein, hereafter referred to as protamone ** on certain gland and organ weights was also reported. In this experiment it was noted that the carcass of the protamone-fed chicks at 12 weeks contained decidedly less fat than the control chicks, indicating that the growth process was being stimulated at the expense of fat deposition. Further, the feeding of protamone had caused a marked suppression of the thyroid gland weight and probably its function. It seemed of interest to determine the effects on body weight, fattening, and gland . . .

MANY investigators during the past three decades have reported on the various effects of feeding fresh or desiccated thyroid to chickens. Results have been variable, dependent upon dosage level and potency of the material. Most of the work reported has concerned adult stock, and the data relative to chicks and young growing stock appears to be meager. Crew and Huxley (1923) fed dried thyroid to 12 chicks and found no significant difference in weight between the control and experimental group. It is known that thyroid given in excessive amount will retard the rate of growth or even cause a loss of body weight. However, some investigators have reported acceleration of the growth rate in dogs, rats, and mice when thyroid was fed in optimum amounts. Recently Koger and associates (1942 (1943) reported improvement of growth and appetite in mice receiving subcutaneous injections of crystalline thyroxine and the feeding of thyroactive . . .

MOST of the procedures for the biosassy of thyrotropin involve subcutaneous or intraperitoneal administration of a series of test doses of the hormone over a period of 3 to 5 days (cf., Albert, 1949; Turner, 1950). Ghosh et al. (1951) developed an assay based on the uptake of I131 by the thyroid of the hypophysectomized rat following a series of 5 subcutaneous injections of thyrotropin. Subsequently, Overbeek et al. (1953) substituted rats prefed with iodocasein for hypophysectomized animals, and administered thyrotropin in 2 intraperitoneal doses. A ten-fold increase in sensitivity was achieved over the method of Ghosh et al. (1951). Recently, Kriss and Greenspan (1954) described a bioassay based on the enhanced uptake of P32 by the chick thyroid following a single intracardiac injection of thyrotropin. The sensitivity of this method was about 10 times that observed after a single intraperitoneal injection of thyrotropin (Crooke and Matthews, 1953).

AT THE Nebraska Station a ration has been used which produced very good growth in chicks. The question arose as to whether still better growth would result from that ration when supplemented with a vitamin concentrate. Accordingly a feeding trial was run to compare the rate of growth and the retention of nitrogen on a ration with the concentrate to that on a control ration. At the same time a question arose regarding the value of the addition to the diet of iodocasein which exhibits some of the properties of thyroxine. Among workers who have studied the effect of iodocasein additions to poultry rations are Turner and co-workers (1945a, 1945b, 1946) and Hutt and Gowe (1948). A review of other work in the field was furnished by Reineke (1946). Much of this work was done with laying hens, with less attention to the effect on newly hatched chicks. Robblee and . . .

1. 1. The action of various iodinated proteins (iodocasein, iodoinsulin, iodothyroglobulin), of natural thyroglobulin and of thyroxin on the metamorphosis of tadpoles of Bufo bufo and on experimental goitre in rats fed on a diet containing 6.N-propylthiouracil has been studied under strictly comparative conditions. 2. 2. Iodocaseins prepared by various methods and containing nearly the same thyroxin percentage are of very different activities when administered by mouth; these differences are less marked and can even disappear when the same products are injected or when submitted to tryptic hydrolysis. The biological efficiency of the iodinated proteins, thus, depends not only on their thyroxin content, but also on the assimilation of the hormone. Previous researches have given results interpreted as showing differences in thyroxin content of iodoproteins when an increase of assimilation was obtained. 3. 3. Iodoinsulin and natural thyroglobulin show, per unit weight of thyroxin, a biological activity greater than free thyroxin. The data obtained in this work lead to the conclusion that the hormone present in these proteins is better utilized than free thyroxin, owing to its progressive penetration in the body fluids during the proteolysis.

THREE recent papers in this journal by Turner et al. (1945, 1945a. 1946) and a review by Reineke (1946) report experiments which led these writers to conclude that iodinated casein, a substance having the properties of thyroxine, has a marked stimulatory effect upon the production of eggs by domestic fowls. In most of the experiments this effect was believed to be exerted chiefly during the months of late spring and early summer, when production normally declines, but in one test (Turner et al., 1946, Lot IV) the treated birds laid better throughout the year. Since any such effect would have considerable economic value, it seemed desirable to repeat the experiments. THE EXPERIMENT Birds.—Single Comb White Leghorn pullets of the C and K strains resistant to lymphomatosis (Hutt and Cole, 1947) were utilized. The total number enrolled at the start of these trials was 401, these being divided in four . . .

ConclusionsRhode Island Red chicks were raised to 12 weeks of age on diets containing from 0.025 to 0.2% of thyroactive iodocasein. Chicks receiving the lower levels, required less feed per gram of gain than did the controls. Those fed diets with 0.1 and 0.2 % thyroactive iodocasein gained more than the controls and were more fully feathered than either the controls or those receiving the lower levels. The thyroactive iodocasein-fed chicks utilized their feed more efficiently than the controls only during the periods when they were gaining at a more rapid rate.Statistical analysis showed the difference in rate of gain to be of doubtful significance although the data indicate that at the proper dosage level growth rate was above normal. The differences in the rate of feathering in favor of the treated birds on higher dosage levels were highly significant.

STUDIES of the distribution and transformation of calorigenic, iodine-containing substances have been handicapped by the fact that pharmacologic doses of material were usually required in order to obtain a concentration of iodine in tissue or body fluids sufficiently high to be measured satisfactorily by current chemical methods. The availability of radioiodine (I131) has made it possible to reinvestigate the metabolism of calorigenic iodine compounds in animals and man under physiologic conditions. Radioiodine can be incorporated into calorigenic materials so as to obtain biologically active compounds with high specific activity. This not only permits the use of physiologic amounts of material, but also permits determination of the distribution of the material and its derivatives with greater accuracy and sensitivity than was previously possible. In addition, radioiodine and substances containing it can, to some extent at least, be observed in vivo by means of a Geiger counter directed at various parts o...

IT IS well known that iodocasein is effective as a thyroid hormone. Reineke et al. (1943) have demonstrated the presence of 1 percent of thyroxine (T4) in this substance. Therefore, when iodocasein is fed directly to adult or growing chickens, metabolic rate is elevated and thyroid involution occurs (Irwin et al., 1943; Mellen and Hill, 1953; Garren and Shaffner, 1956). On the other hand, the goiter developed by iodocasin feeding has been reported. It is claimed that the high iodide content of iodocasein might be responsible for its goitrogenic influence (Wheeler and Hoffmann, 1948Wheeler and Hoffmann, 1950). The present paper reports the effects of iodocasein on iodine metabolism when it was added to the diets of broiler chicken. MATERIALS AND METHODS Nichols commercial chickens (♀ 108 × ♂ 909) hatched on October 9th were kept in heated brooders until reaching 7 weeks of age. They were fed an all-mashed basal ration with . . .

SummaryImmature virgin female mice were treated with thyroactive iodocasein by both oral and subcutaneous administration and their growth compared to that of controls. The treated animals gained significantly more in body weight and in total length than the non-treated controls.

Considerable recent literature has been devoted to effects of a thyroactive iodocasein (Protamone) and thiouracil on the growth, fattening, and feathering of broilers, vide Parker (1943), Irwin, Reineke, and Turner (1943), Turner, Irwin, and Reineke (1944), Kempster and Turner (1945), and Andrews and Schnetzler (1946). One immediate effect of these substances in the diet is exerted upon the activity of the thyroid and when the substances are fed at proper levels it is possible to produce mild hypothyrosis or mild hyperthyrosis in chickens. The above literature suggested that a further effect of these substances in the diets of chickens might be tested, namely, their effect on resistance to parasitism. It has been reported, Larsh (1947), that the daily addition of 3 mg of thyroid to the diets of mice resulted in a much higher percentage development of Hymenolepis than occurred in control animals. The present writer (1948a, in press) will report significantly superior growth of parasitized chicks with a mild hyperthyrosis when compared with growth of parasitized normal controls, and, when compared with growth of parasitized chicks with a mild hypothyrosis. Wheeler et al (1948) reported that 0.1 percent thiouracil in the diet of 2-week old chicks was not prejudidicial to the survival of birds artificially infected with cecal coccidiosis, while their data on 0.02 percent Protamone in the diet suggested that birds on such a diet were somewhat resistant to the same infection.