GAS-PRODUCTION AND NITROGEN DIGESTION BY RUMEN MICROBES FROM DEER ANDSHEEP

The rates at which gas was produced by rumen microbes from red deer (C ervus elaphus) and sheep were measured in vitro. The objective was to test the hypothesis that the lower frequency of rumen eructation contr actions in deer, compared to sheep and other ruminants, may have been associated with a lower rate of gas production. Two sheep and two deer were held indoors, given the same feed (chaffed lucerne hay) under an identical regimen, and rumen samples obtained on 5 consecutive days f rom each animal. Duplicate incubations were carried out on each day wi th a rumen liquor inoculum from each animal in a buffered medium and a ground lucerne hay substrate. The rates of gas production were monito red for 9 h and net ammonia production determined. There were no diffe rences between species in rate of gas production but incubation with d eer liquor resulted in a 27% greater (P < 0.01) net conversion of subs trate nitrogen (N) to ammonia compared to sheep. Gas production averag ed 0.23 ml/min per g substrate between 1 and 3 h of incubation and dec lined to 0.15 ml/min per substrate after 7 h. Ammonia release over the incubation period resulted in 22 and 17% of the substrate N appearing as ammonia-N from deer and sheep incubations respectively (P < 0.01). The difference between deer and sheep in the frequency of rumen eruct ation contraction sequences does not appear to be related to rates of gas production in the rumen.