Flow of microbial and non-microbial N fractions entering the omasal canal in dairy cows

Abstract

In order to provide accurate estimates of protein supply for lactating dairy cows, the effect of feed ingredients on ruminal protein degradability as well as microbial protein synthesis must be determined. The omasal sampling technique coupled with a triple marker method allows the determination of N flow from the reticulorumen with relatively small contribution from endogenous sources (Ahvenjärvi et al., 2000). The objective of the current study was to assess the contribution of microbial and non-microbial fractions to the total flow of N leaving the rumen of lactating dairy cows fed typical feed ingredients.