Thyroid function was examined in fetal and newborn young of dams fed diets containing 24% or 4% casein as the sole source of protein. Radioactive iodine uptake, as examined autoradiographically and by gamma counting, was significantly reduced in glands of progeny of deficient rats. Following injections of thyrotropin or thyrotropin releasing hormone, thyroid cells of newborn young of protein-deprived rats contained fewer colloid droplets than those of control pups. Circulating levels of triiodothyronine and thyroxine were significantly reduced in the plasma of newborn young of protein-deprived females as compared with controls.

Comparisons were made among isonitrogenous (1.6%) diets containing isolated soybean protein (ISP), soybean flakes, soybean nuts, tofu and bovine nonfat dry milk (NFDM). Each diet was fed for 3 wk at different levels of intake to male weanling rats and change in body weight was related to dry matter intake by linear regression. The slope of the regression line was designated as the weight gain coefficient. For the tofu and soybean flake diets, the weight gain coefficient was 65%, for the ISP diet 76%, and for the soybean nut diet 86% of that obtained for the NFDM diet. Since diets were isonitrogenous, differences among weight gain coefficients were attributed to differences with which the various sources of protein influenced the utilization of diets to promote body weight gain. There was no correlation between weight gain coefficient and trypsin inhibitor activity, supporting the conclusion that variation in the nutritional quality of soybean products is not directly related to trypsin inhibitor activity. Soybean products are becoming increasingly important in human diets, thus further investigation of factors affecting their nutritional quality is warranted.

The question of whether or not meal frequency influences body composition and feed efficiency has been of interest to several researchers. A few studies have indicated that body composition has been influenced by alterations in the meal patterns of force-fed rats ( 1 -3); whereas, other studies have indicated that in pair-fed rats (4) and pigs (5) that meal frequency does not alter body composition. The purpose of this study was to determine the influence of restricted meal frequency on body composition, gross feed efficiency, and energy utilization and maintenance requirements in male weanling rats.Material and methods. Seventy male weanling rats of the Sprague-Dawley strain weighing 50 2 5 g were randomly placed into one of four groups. Group I consisted of 23 nonfasted male rats which were sacrificed by cervical dislocation at the beginning of the study, Day 0. These animals were used to predict initial carcass weight, lean weight, and body energy for rats in groups I11 and IV. Group I1 consisted of 12 male rats which were provided food ad libitum for 3 weeks. These rats were used to determine restricted feed intakes for rats in groups I11 and IV. Rats fed one time per day and four times per day were given 46, 67, and 87% of ad libitum food intake. Group I11 consisted of 18 rats fed one time per day (1 x /day) at three different restricted levels of feed intake for 21 days. These male rats were given food at 1800 hr. Group IV consisted of 17 rats given food four times per day (4 x/day) at three different restricted levels of intake for 21 days. These rats were given food at 0600, 1200, 1800, and 2400 hr. Animals in groups I11 and IV were fed equivalent amounts of the same diet.Rats in groups 11, 111, and IV were housed individually in suspended wire cages in animal quarters that were maintained at 27°C and lighted from 0700 to 2100 hr. They were fed a diet containing 24% casein as shown on Table I, and always had free access to water. Rats were weighed weekly and feed intakes were recorded. Paper liners were placed below the suspended wire cages and daily spillage was determined. At the end of 3 weeks, Day 21, these rats were killed by cervical dislocation.Prior to analyses, gastrointestinal (GI) tracts were removed from all rats. GI contents were discarded and empty GI tracts were returned to the carcasses. The carcasses were then weighed to determine final carcass weights.For each animal, the metabolic body size (W0.75) was computed by raising to the 0.75 power the mean body weights in kilograms during the feeding trial.Carcasses were lyophilized for 7 days. 'The dried carcasses were extracted for 7 days with ether and 5 days with acetone. The final fat weights of the rat carcasses were calculated as the differences in the weights of the dried carcasses before and after extraction. The difference between the total weight of a carcass (including moisture) and the weight of the extracted fat was the fat-free carcass weight.Determining gross feed efficiency. Gross feed efficiency was calculated by subtracting i...

EXPERIMENTAL Isocaloric diets containing various levels of protein supplied as commercially prepared defatted corn germ flour (CGF), CGF 'supplemented with 0.07% methionine and O.O2%*leucine (SCGF), casein (C) or lactalbumin (LA) were compared in this study. Weight gains of weanling rats fed various growth-limiting amounts of protein were used to determine a protein value, defined as the slope of the regression line relating weight gain to protein intake, for each of the protein sources. The PV of CGF was significantly different from that of LA, but did not differ significantly from the PV of SCGF and C. The relative protein value of CGF, the ratio of the PV of CGF to the PV of LA, is 0.62 + 0.06. These data indicate that the protein in commercially prepared CGF is of good quality and could be a valuable source of protein for human diets.