Influence of the pattern of peptide supply on microbial activity in the rumen simulating fermenter (RUSITEC)

The source and pattern of N supply was varied in the rumen simulation technique (RUSITEC) in order to determine if continuous, rather than transient, availability of peptides was required for optimum ruminal fermentation. The energy source was fibre prepared from sugar-beet pulp. N was added as NH(3) continuously infused (AC) or peptides (Bacto(R) Casitone, a pancreatic hydrolysate of casein; Difco Laboratories, Detroit, MI, USA) continuously infused (PC) or added as a single dose at the time of feeding (PS). Free peptides were detected in the fermenter liquid for 4 h after feeding in the AC treatment, for 10 h in the PS treatment, and at all times with the PC treatment. Treatments had no effect on DM degradation. Approximately 40 % of the degradation occurred during the time no peptides were detected in the PS treatment. Microbial N flow tended to be higher with the peptide additions (P