A feral goat rumen fluid inoculum improves nitrogen retention in sheep consuming a mulga (Acacia aneura) diet

Abstract

Rumen micro-organisms which are resistant to high levels of condensed tannins (CT) may constitute a unique response by feral goats to the nutritive depressing effects of mulga (Acacia aneura) CT. Transferring these micro-organisms to domestic livestock lacking this response may be beneficial when CT-rich mulga diets are consumed. Three experiments were conducted in which sheep consuming a mulga diet were given a ruminal inoculation of feral goat rumen fluid (FGRF). Feed intake and nitrogen (N) retention were significantly greater (P < 0.05) in both sheep and domestic goats following inoculation and in inoculated compared with uninoculated sheep. Inoculation also improved N digestibility and reduced the rate of liveweight loss in sheep and domestic goats. These improvements were of similar magnitude to those attributable to the traditional N, phosphorus and sulfur mineral supplement for mulga fed sheep. FGRF inoculated sheep also grew as much wool as uninoculated sheep receiving a production enhancing mineral supplement. The results from these experiments suggest that FGRF is readily transferable to sheep and improves N metabolism in these animals. Using micro-organisms from FGRF as an inoculum for sheep consuming a mulga diet has the potential to be an alternative to mineral supplements.