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Typescript (photocopy). / Digitized by Kansas Correctional Industries

Experiments were designed to investigate the possibility of using mice as model animals for the evaluation of protein quality, and to compare it with rats under the same conditions. Parameters measured were protein efficiency ratio, net protein ratio, protein digestion and relative protein value. Six sources of protein were tested at three dietary levels for each. Measurements were taken at four different periods of feeding, thus, the effects of dietary level of protein and the length of the feeding period were studied. Results on mouse experiment indicated that the highest PER values were obtained at 6 and 8% levels of dietary protein with significantly lower values when 11% levels were fed. The highest NPR values were obtained at 6% level of dietary protein then declined when 8 or 11% levels were fed. The highest efficiency regarding PER and NPR were obtained when mice were fed for 10 days than when they were fed for 14, 21, or 28 days of experiment. High quality protein sources were needed at lower levels in the diet for shorter periods of time to obtain the maximum efficiency when compared to poor quality sources of protein. Results for protein digestion did not correlate with those of PER, NPR or RPV indicating that protein digestion is a poor measurement. However, PER, NPR, and RPV were highly correlated. Results of rat experiment were in agreement with what was reported in the numerous works for rat bioassay in the literature review. Rate of body weight gain increased with increasing levels of dietary protein and the PER reached a maximum value, then decreased. Values of NPR tended to fall with increasing levels of dietary protein. PER values tended to increase gradually with prolonged period of feeding, then decline. The maximum PER values were obtained when 10% level of dietary protein was fed for a period of 15 days. Likewise mice experiment, PER, NPR, and RPV correlated highly while protein digestion correlated poorly with the other methods used. In general mice appeared to be influenced by the same factors as rats when used for the evaluation of protein quality. Mouse could be used as a model animal for protein quality evaluation with the advantages of small animal size, lower feed intake, shorter period of feeding, plus is highly desirable for experiments involving the use of isotopes or whole carcass analysis. A dietary protein level of 8% for a feeding period of 10 days would be suitable for use with mice instead of a 10% dietary level for a 28 day feeding experiment in rats. Whole eggs could be used as a suitable reference standard protein for mouse bioassay.

The flux of free and peptide amino acids across the stomach and intestinal tissues was quantified using sheep and calves maintained in "steady state” conditions by feeding at hourly intervals. Crossbred wethers and Holstein steers were surgically cannulated in the abdominal aorta, mesenteric vein and portal vein. All animals were fed an orchardgrass, corn, SBM-based diet. The steers received three abomasal infusions; a control solution, and an amino acid mixture simulating casein and casein each at a rate equivalent to 25% of daily crude protein intake. Nutrient fluxes from the mesenteric and portal-drained viscera were measured; non-mesenteric flux was calculated as the difference between portal flux and mesenteric flux. Results of this study support the concept that free amino acids are absorbed by the small intestine and not by the stomach. The flux of peptide amino acids across the portal-drained-viscera indicate that a major portion of the amino acids which are absorbed by cattle and sheep are absorbed in the form of peptides from the stomach. The observation that large quantities of peptide amino acids are absorbed from the stomach is unique and it is expected that this most important discovery will revolutionize the feeding of ruminants. / Ph. D.

Typescript (photocopy). / Digitized by Kansas Correctional Industries

Typescript (photocopy). / Digitized by Kansas Correctional Industries

Call number: LD2668 .T4 1956 H39 / Master of Science

Call number: LD2668 .T4 1958 S79

Call number: LD2668 .T4 1979 G53 / Master of Science

Call number: LD2668 .T4 1979 N53 / Master of Science