Duodenal flow and digestibility in fauna-free sheep and in sheep monofaunated with Entodinium caudatum or Polyplastron multivesiculatum

Abstract

Three groups of five rumen and duodenum cannulated fauna-free sheep were used in a 28d experiment. One group remained fauna-free, whereas the second (EN) and third (PP) groups, respectively, were inoculated intraruminally with the protozoan species Entodinium caudatum and Polyplastron multivesiculatum . Rumen fluid, duodenal digesta and faecal samples were collected during the last 12d. The flow of digesta to the duodenum was determined using Yb and Co as dual-phase markers. 15 Nitrogen and phosphatidylcholine were used as markers to calculate the duodenal flow of bacterial and protozoal N, respectively. Results showed an increase ( P <0·1) in the rumen concentration of NH 3 -N and total volatile fatty acids, and a decrease ( P <0·05) in the duodenal flow of non-NH 3 -N and bacterial N in sheep with EN and PP monofaunas, compared with fauna-free sheep. There were no differences ( P >0·05) in these variables between the two monofauna groups. Protozoal N accounted for 8% of the duodenal non-NH 3 -N flow in the EN-monofaunated sheep, whereas no such flow was detected in the PP-monofaunated sheep. Apparent rumen digestibility of organic matter, neutral detergent fibre and acid detergent fibre were similar ( P >0·05) in the monofaunated groups of sheep, but rumen acid detergent fibre digestibility was higher (P<0·05) in the monofaunated than in the fauna-free groups. Experimental results suggested that, unlike EN, the PP monofauna might not contribute to the duodenal flow of microbial protein, whereas both monofaunas showed a virtually equal degree of predation on rumen bacteria.