Document Type

Thesis - Open Access

Award Date


Degree Name

Doctor of Philosophy (PhD)

Department / School

Animal Science


Feeding experiments, digestion-nitrogen balance trials, rumen fermentation studies and blood parameter determinations were conducted to evaluate protein utilization by cattle and sheep as affected by feed source represented by ingredients varying in solubility or degradability or protein and amino acid profile, processing treatment and level of supplementation. Growing and finishing cattle shower improved performance when fed ground ear corn or corn silage as basal diets supplemented with various sources of protein. Higher rates of gain and lower feed requirements were observed for cattle fed diets supplemented with urea, soybean meal, heat-treated soybean meal, heat-treated mix of 60% soybean meal and 40% soybeans, urea-dehydrated alfalfa meal and soybean meal-dehydrated alfalfa meal in comparison to cattle fed the control diets. No difference (P>.05) in animal performance was observed among the protein-supplemented diets. Data obtained for these diets tested through nutrient digestibility and nitrogen balance trials with lambs shown that, generally, there were no improvements in organic matter apparent digestibility from any of the sources of protein supplementation. Crude digestibility, in general, was higher for diets supplemented with protein than for control diets, with only slight differences among protein-supplemented diets. Protein supplemented resulted in elevated levels of nitrogen being retained as a percentage of the total nitrogen consumed for lambs fed the various sources of supplemental protein as compared to those which received only the control diets. Rumen fermentation studies showed that lambs fed the various supplemental sources of protein had lower rumen pH and higher concentrations of rumen lactic acid, rumen ammonia-nitrogen and total volatile fatty acids than those which consumed control diets. Increased propionic acid and decreased acetic acid molar percentage concentrations were observed for lambs fed the protein-supplemented diets, resulting in significantly lower acetic to propionic acid ratios for these groups. Hourly rumen fermentation studied showed that ruminal activity was at the maximum level between 2 to 4 h after feeding. Since during this period lower rumen pH together with higher lactic acid and total volatile fatty acid concentrations were observed. There were come differences in the rate of fermentative activity in the rumen between dietary treatments at each sampling period with protein-supplemented lambs showing greater activity. In studies conducted to evaluate growing-finishing lamb responses to soybean meal or urea at various levels of supplementation, it was observed that these sources appeared to be of similar value, since there were essentially no differences in average daily gain, feed intake or feed efficiency between the two supplements. Feeding lambs diets containing increasing levels of protein (from 11.2 to 15.1%) resulted in improved average daily gain, increased feed intake and lower feed requirements. However, the rate of improvement in average daily gain decreased at the higher level (15.1%) may have approached or exceeded protein requirements for the lambs. No indication of a period of adaptation was noticed during the feeding trial for lambs fed urea up to 1.08% of the dry diet. Under conditions of adaptational digestion-nitrogen balance studies, it was also observed that there appeared to be no evidence of a period of adaptation to diets with the various levels of protein from soybean meal or urea as measured by nutrient digestibility and nitrogen balance. Lambs receiving diets with urea had slightly high digestibility for organic matter but similar digestibility for crude protein and for nitrogen balance as lambs fed soybean meal supplemented diets. In general, feeding diets containing 12.5, 13.8 and 15.1% protein to lambs resulted in improved nutrient digestibility and nitrogen balance as compared as compared to diets containing 11.2% protein. During these lamb studies, nitrogen supplementation, particularly urea, resulted in increased rumen ammonia-nitrogen concentrations. Higher blood urea-nitrogen was observed for lambs fed increasing levels of protein, whereas protein supplementation at the levels fed during this research appeared to have no effect on plasma ammonia-nitrogen concentration.

Library of Congress Subject Headings

Cattle -- Feeding and feeds

Cattle -- Growth

Sheep -- Feeding and feeds

Sheep -- Growth



Number of Pages



South Dakota State University