Postprandial changes in particle associated ruminal bacteria in sheep fed ammoniated rice straw

An experiment was conducted to quantify postprandial changes in particle attaching ruminal bacteria in sheep fed untreated (UTS) and ammoniated (ATS) rice straw. Diaminopimelic acid (DAPA) was used as a marker for the calculation of mass of tightly associated bacteria (TAB). ATS feeding decreased large particle proportion, while increased fine particle proportion. Ammoniation of rice straw had a significant effect on mass of non-associated bacteria (NAB), loosely associated bacteria (LAB) and tightly associated bacteria (TAB) with feed particles, showing the higher values in ATS-fed sheep within 2–5 h after feeding. Significantly increased bacterial densities associated with small and fine particles were also observed, indicating that size of particles is an important factor for the attachment of bacteria. The current study suggests that ammoniation accelerates particle size reduction of rice straw in the rumen, stimulating colonization of bacteria onto the smaller particles and overall degradation of rice straw fragments.