In situ rumen degradation of amino acids from different feeds corrected for microbial contamination

Abstract

Variations of the amino acid profile produced by rumen actions were established for fish meal (FM), corn grain (CG), corn gluten feed (GF), dehydrated beet pulp (DBP), and lucerne hay (LH), using the nylon bag technique. The effects of degradation of soluble or insoluble proteins were mea- sured by rumen incubations at 0 h (washout value) and 16 h, respectively. Rumen incubations were performed on four cannulated wethers and the microbial contamination of incubated residues was cor- rected using a continuous 15 N-intraruminal infusion and solid associated bacteria isolates as the ref- erence sample. The results showed that rumen degradation of both soluble and insoluble proteins pro- duced changes in the amino acid profile, which were not uniform among feeds. Differences between feed and insoluble protein amino acid composition were limited for FM and DBP, important for GF and LH, and intermediate for CG. Differences between insoluble and undegraded protein amino acid composition were also limited for FM, GF, DBP, and LH and important in CG. The results showed that the amino acid profile in the undegraded protein and in the whole feed should be close for FM, DBP and LH. On the contrary, in CG, important variations are expected, since both solubility and degradability effects produced changes with the same tendency for most of the essential amino acids. In particular, our results showed a great decrease in the lysine content of the undegraded protein, which increases the lysine deficiency of this feed. This decrease of lysine was also evidenced in GF. rumen degradation / amino acid profile / microbial contamination / 15 N