Volume 88, Issue 1, July (2002), pp. 73-80 © The Author 2002

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

Juan P. Russi, R. John Wallace and C. James Newbold^*
Rowett Research Institute, Bucksburn, Aberdeen AB21 9SB, Scotland, UK

 (Received 7 December 2000–Revised 14 January 2002–Accepted 7 February 2002)

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 NH₃ continuously infused (AC) or peptides (Bacto^® 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<0·061), with no significant difference between the two peptides treatments. The production of liquid-associated micro-organisms (LAM) was higher in the PC treatment (P<0·05) and the proportion of LAM derived from NH₃ lower (P<0·05). However, LAM only accounted for 20–30 % total microbial population. Our main conclusion was that peptides had a small stimulatory effect on the fermentation, but there was no indication that synchrony of supply of energy and amino acid-N in the fermenter promoted a more efficient fermentation than non-synchronous supply. This conclusion must be qualified, however, because some N remained in the fibre and may have become available progressively as the fibre was digested by the micro-organisms.

Abbreviations: AC; ammonia continuously infused; LAM; liquid-associated micro-organisms; PC; peptides continuously infused; PS; peptides as a single dose; RUSITEC; rumen simulating fermenter; SAM; solid-associated micro-organisms

Corresponding author:  Dr C. James Newbold, fax +44 1224 716687, email cjn@rri.sari.ac.uk

Keywords:
Synchrony: Microbial protein synthesis: RUSITEC