No description available.

No description available.

No description available.

The present investigation was conducted to determine the extent to which the effects dietary protein level and amino acid balance have on rate of growth and efficiency of feed conversion can be related to the effects they have upon thyroid activity and tissue respiration. Thyroid activity and body weight were studied in chicks fed diets containing 17.5% and 26% of protein and variously supplemented with amino acids. The basal diets were deficient in methionine and glycine. Growth was stimulated at both protein levels by the addition of methionine or methionine plus glycine to the basal diets. Even when supplemented with amino acids, the low-protein diet was inadequate for maximum growth. Thyroid weight, thyroid weight relative to body weight and I¹³¹ uptake per chick were increased when the protein level was increased from 17.5% to 26% but uptake of I¹³¹ per unit weight of thyroid gland was not affected. Supplementation of the diets with lysine significantly reduced thyroidal uptake of I¹³¹ per chick. Addition of methionine or methionine plus glycine reduced uptake of I¹³¹ per unit weight of thyroid gland. The effect of various levels of dietary lysine, methionine and tryptophan on body weight, efficiency of feed conversion, nitrogen balance and metabolizable energy were studied in relation to concurrent effects of diet on thyroid activity and tissue respiration in chicks. Respiration of liver slices and fiber bundles of skeletal muscle was measured with a Warburg respirometer. Feed and feces were analyzed for nitrogen by the macro Kjeldahl method and for combustible energy with a Parr oxygen bomb calorimeter. Addition of lysine to diets deficient in lysine significantly improved body weight, efficiency of feed utilization, and nitrogen retention in chicks fed the experimental diets. Addition of 0.30% lysine to diets containing 1.09% of lysine improved body weight significantly but had no significant effect on the other parameters mentioned. Addition of methionine to a diet containing 1.39% of lysine improved feed efficiency in birds 17 to 22+ days of age. Amino acid balance had no effect on metabolizable energy. Birds fed lysine deficient diets had lighter thyroids and lower thyroidal uptake of I¹³¹ but had higher uptake of I¹³¹ per mgm. of thyroid gland than those fed diets containing 1.09% or more of lysine. Amino acid balance had no effect on oxygen consumed by muscle tissue, but a deficiency of lysine significantly increased oxygen consumed by liver slices taken from 6 and 8 week old chicks. It is concluded that amino acid composition of dietary protein, as well as the protein level in the diet, affects thyroid activity in the chick. Amino acid imbalance caused by dietary lysine deficiency results in high thyroid activity, low body weight, poor efficiency of feed conversion, and poor nitrogen retention but apparently high respiration of liver slices. Possible shifts in methionine and lysine requirements during the first 25 days after hatch were investigated. It was found that the requirement of the chick for methionine did not change during this time hut that the requirement of the chick for lysine was higher in birds 0 to 20 days of age than in older birds. / Land and Food Systems, Faculty of / Graduate

Two feeding trials were conducted with 30-week-old single comb white leghorns fed two basal diets containing 8% of hydrogenated coconut oil or safflower oil. These basal diets were fed with or without supplements of \% cholesterol (ch), 2-fo soysterols (st) or in combination (ch+st). Trial 1 was designed to study the sensitivity of laying hens in response to dietary lipid factors and to compare the mode of changes in serum and egg yolk concentrations by weekly determination of their sterol levels during a feeding period with no soysterol supplementation followed by a period with soysterol supplementation. Objectives of trial 2 were to study the effects of dietary lipid factors on the serum and egg yolk levels and to delineate their roles or mechanisms. Changes in egg yolk sterol levels caused by dietary lipid factors were generally parallel to, and preceded by, those in serum sterol levels. This indicated that the egg sterols originated from the circulating labile sterol pool. Safflower oil suppressed and hydrogenated coconut oil elevated the sterol levels in both serum and egg yolk. Cholesterol feeding with dietary safflower oil increased the absorption of cholesterol, resulting in an increase of serum and egg sterol levels as compared to sterol levels of hens fed Hydrogenated coconut oil. Dietary soysterols supplementation resulted in a decrease in both serum and egg yolk sterols which was demonstrated in the presence of dietary cholesterol as well as cholesterol-free treatments. The apparent absorption of cholesterol was not retarded by the simultaneous feeding of cholesterol and soysterols. However, soysterol feeding accelerated the fecal excretion of bile acids and catabolic products of neutral sterols. The apparent absorption of plant sterols was 11%. Absorbability Of plant sterols in laying hens was further supported by detection of these sterols in tissue and egg yolk. The absorption of the plant sterols was, however,. Slightly decreased when cholesterol was fed simultaneously. Cholesterol feeding increased total lipid content in liver and serum, whereas soysterol feeding reduced or diminished lipid accumulation caused by the cholesterol treatment. Both dietary cholesterol and soysterols altered the fatty acid composition of liver, serum and egg yolk lipids by increasing oleic acid and decreasing palmitic and/or stearic acids. These changes were significantly greater upon feeding cholesterol than soysterols. However, the simultaneous feeding of cholesterol with soysterols exerted the least effect on the fatty acid composition in liver. The possibility that soysterols affected biosynthesis and/or oxidative catabolism of fatty acids in the liver of laying hens in a similar fashion as cholesterol was discussed. / Land and Food Systems, Faculty of / Graduate

The biological activity or availability or feedstuff selenium was determined by comparing the effectiveness of the feedstuff with that of dietary sodium selenite in preventing the incidence of exudative diathesis in the chick. The available selenium in ten wheat samples varied from 62 to 178 percent with a mean of 105 percent. The selenium availability in rapeseed meal ranged from 27 to 89 percent with a mean of 61 percent. Selenium metabolism in the chick was investigated by adding graded levels of sodium selenite to the basal selenium deficient diet and comparing the dietary selenium concentration to the selenium concentration in the tissues (l.e. Blood, liver, kidney, and muscle of the chicks). The selenium content in the tissues examined increased proportionately to an increase in dietary selenium supplementation from 0 to 0.2 ppm. Blood and liver selenium concentration remain relatively constant (a slightly increasing plateau) from 0.2 to 1.0 ppm of dietary selenium. Above 1.0 ppm dietary selenium, blood and liver selenium levels increase steadily. These results show that either blood or liver selenium levels represent the selenium status of the bird. A similar response in tissue selenium levels of the chick was observed when selenium was supplied either as sodium selenite Or a feedstuff (brewers yeast). Furthermore, selenium levels birds fed wheat diets were similar to those fed equivalent selenium (sodium selenite) supplied in the basal diet. / Land and Food Systems, Faculty of / Graduate

No description available.

Four studies were performed to examine peripheral factors involved with food intake regulation in the domestic fowl. In the first study, the mechanism by which tryptophan depresses food intake was clarified. Intraperitoneal injections of tryptophan methyl ester were demonstrated to inhibit feeding in Single Comb White Leghorn (SCWL) cockerels. Intragastric intubations of tryptophan inhibited food intake and decreased body temperature of SCWL cockerels. These results, in conjunction with previous findings, indicate that tryptophan's inhibitory influence on food intake is peripherally rather than centrally based. The second study explored the role of the duodenum in food intake regulation. Intraduodenal glucose loads had no effect on food intake of SCWL or Rock Cornish (RC) commercial broiler cockerels. In addition, splanchnicectomized birds did not respond to intraduodenal glucose infusions any differently than sham-operated controls. Apparently, the duodenum does not play a significant role in food intake control in the fowl. Hepatic involvement in appetite regulation was examined in SCWL and RC cockerels in the third study. Amino acid solutions failed to influence food intake when infused intraportally in either strain of chicken. Relatively small glucose or lipid solutions depressed food intake significantly when infused intraportally in the SCWL birds but had no effect in the RC cockerels. The liver appears to be integrally involved in controlling food consumption in the SCWL chicken. In the final study, the existence of a "hunger" factor in the peripheral circulation of two lines of chickens divergently selected for body weight was explored. Intrahepatic infusions of plasma from food deprived high-weight line chickens stimulated food intake of sated low-weight line chickens. These studies indicate that peripheral mechanisms are important in regulating appetite in light-breed chickens such as the SCWL, however, such mechanisms in heavy-breed chickens such as the RC appear to be less sensitive. This desensitization in heavy-breed chickens suggests that genetic selection for increased growth has affected the food intake control systems. / Ph. D.

Call number: LD2668 .T4 1948 S35 / Master of Science

Call number: LD2668 .T4 1952 L48 / Master of Science