Effects of diet fermentability and supplementation of 2-hydroxy-(4-methylthio) butanoic acid and isoacids on milk fat depression in lactation dairy cows: 1. Rumen fermentation, fatty acid profile, and bacterial population

Increasing 18 t10 isomers was not the factor causing moderate MFD for LF vs. HF when PUFA level was similar. Supplementation of HMTBa increased biohydrogenation capacity with minimal changes in bacterial community. Supplemental IA increased bacterial diversity and functional features but increased rumen 18 t10 isomers. The combination of HMTBa and IA had associative effects in the rumen and need further studies to understand the interactive mechanism.