AN IN-VITRO CULTURED RUMEN INOCULUM IMPROVES NITROGEN DIGESTION IN MULGA-FED SHEEP

Mixed cultures of anaerobic micro-organisms were derived from feral go at rumen fluid (FGRF) using a laboratory fermenter to selectively cult ure microbes actively degrading mulga, and were evaluated as rumen ino cula in digestion and liveweight studies with mulga-fed sheep. When pl aced in the rumen of sheep, FGRF enhances mulga digestion; however, li mited supplies of feral goats, the labour involved in locating and mus tering goats, and likely variations in the microbial composition of FG RF between animals and localities make the production of an in vitro c ultured inoculum a desirable alternative to enable widespread adoption . The cultured inoculum significantly (P < 0.05) improved nitrogen dig estion and retention in mulga-fed sheep by 16 and 76%, respectively. I nocula consisting of simplified mixtures of bacteria isolated from she ep, feral goats, and native marsupials did not affect mulga digestion. In the first of 2 liveweight studies, sheep inoculated with the ferme nter inoculum lost significantly less weight than uninoculated sheep f or the first 57 days (0.3 v. 4.6 kg); however, after 83 days the diffe rence in the rate of liveweight loss between the fermenter inoculum gr oup and the uninoculated sheep was not significant (53 v. 95 g/day). I n the second study, liveweight loss was not significantly reduced by t he fermenter inoculum. An inoculum based on FGRF, and produced in. vit ro using a fermenter, is potentially valuable to grazing enterprises r eliant on mulga-fed sheep. However, problems in generating a consisten t inoculum need to be addressed before such an inoculum can be general ly considered.