Chemical composition of bacteria harvested from the rumen of dairy cows fed three diets differing in protein content and rumen protein degradability at two levels of intake

Abstract

The content of nitrogen (N), lipids, starch, DAPA and RNA were examined in liquid‐associated bacteria (LAB) and solid‐adherent bacteria (SAB) isolated from the rumen contents of six dairy cows fitted with rumen and duodenal cannulas. Treatments comprised three concentrate mixtures differing in the amount of rumen degradable intake protein (DIP): 134, 114 and 101 g kg⁻¹ DM, respectively. Measurements were taken at high feeding level (19.7 kg DM d⁻¹) and repeated at low feeding level (10 kg DM d⁻¹) with the same animals and diets. The SAB contained more lipids and starch (P < 0.05) but less N, DAPA, and RNA than LAB (P < 0.05). Decreased feeding level reduced the concentration of N, lipids, starch, and RNA in the bacterial populations (P < 0.05). Increased levels of DIP in the concentrate mixtures increased the concentration of N and RNA in the bacteria.