Opportunities to improve nitrogen utilisation in the rumen by reduction in plant-mediated proteolysis

Abstract

The reaction of ingested forage plant fragments to the rumen environment may contribute to the rapid degradation of plant cell contents in the rumen. A series of experiments were used to explore the hypothesis that plant-mediated proteolysis (PMP) contributes to N loss from fresh forage entering the rumen, and to investigate the potential for identifying cultivars with reduced PMP. During an in sacco time-course experiment, chopped fresh field grown perennial ryegrass (Lolium perenne L.) leaf samples lost 15% of their total N within the first 8 hours in the absence of rumen microbes; whereas 40% was lost from samples incubated with exposure to rumen microbes. Accumulation of free amino acids in the buffer accounted for 75% of the N loss after 24 hours. In a subsequent experiment, in vitro incubation of samples from five perennial ryegrass cultivars detected significant (P