Degradable Protein for Dairy

The effects of feeding different proteins on milk production were tested in a 5x5 Latin square designed study with ten ruminally-cannulated lactating Holstein cows. The cows were fed total mixed rations containing on a dry-matter basis: 44% corn silage, 22% alfalfa silage, 2% urea and 31% concentrate. The concentrate contained 31% high moisture corn and one of four test protein supplements (9% solvent soybean meal, 10% expeller soybean meal, 5.5% blood meal and 7% corn gluten meal) included at the expense of the high moisture corn. Omasal sampling was used to quantify total amino acid nitrogen and nonammonia nitrogen flows from the rumen. Estimates of rumen-undegradable protein were made from the differences between total and microbial nitrogen flows. The research group used three different methods to calculate microbial nitrogen flows. They estimated rumen-undegradable protein values for solvent soybean meal, expeller soybean meal, blood meal and corn gluten meal at 27, 45, 60 and 73%, respectively. In these studies, a high percentage of the soybean meal is not degraded in the rumen and passes into the lower gut for subsequent digestion. Thus the quality of the soybean protein is important in meeting the cow’s daily nutrient requirements for milk production.

Reynal, S.M. and co-workers. J. 2003. Effect of feeding protein supplements of differing degradability on omasal flow of microbial and undegraded protein. Dairy Sci. 86(4):1292-1305.