Two ruminally cannulated Holstein cows ( ∼202 DIM) were used to determine the in situ degradability of five protein supplements: blood meal, meat and bone meal, corn gluten meal, expeller soybean meal, and solvent extracted soybean meal. Dacron bags containing 4 g of each supplement in duplicate were soaked in water and then incubated in the rumen for 0, 3, 6, 12, 18, and 24 h for 3 d. Four extra sample bags of each supplement were incubated in the rumen for 12 h to determine the in vitro intestinal digestibility and AA analysis of the residues. Protein supplements were also analyzed for their AA content. Ruminal degradability of individual supplements varied. Solvent soybean meal was the most degradable, and blood meal was the least degradable. Specific first- limiting essential AA were isoleucine for blood meal and meat and bone meal, lysine for corn gluten meal, and methionine for the soybean meals. The RUP fraction in solvent-extracted and expeller soybean meals tended to be more intestinally digestible than did the protein in blood meal and meat and bone meal. In general, all protein supplements, except solvent- extracted soybean meal, were high in RUP and had the potential to provide good quality AA to complement microbial AA for production.
Bibliographical noteFunding Information:
The authors gratefully acknowledge Fats and Proteins Research Foundation, Inc. (Bloomington, IL) for partial financial support of this research. Appreciation is extended to Fenton Ludens, herdsman, and the farm crew at South Dakota State University Dairy Research Unit for the management of the cows and assistance with collection of the data.
- Amino acid
- Protein supplements
- Residual intestinal digestibility
- Ruminal degradation