A Mimosa Bark extract (MB) was given to sheep and cattle to provide condensed tannins (CT) at levels which increased growth in lambs. The effects on rumen metabolism in sheep and milk production in grazing cows were studied in two experiments during spring 1994. MB contained 507g CT/kg bark and was administered as a water suspension (280g/litre). In Experiment 1, six rumen fistulated wethers were offered fresh pasture for two periods of 10 and 14 days, during which each sheep was drenched twice daily with 12.5 ml of either water or MB suspension (4.1 g CT/kg pasture DM intake), in a cross-over design. MB did not significantly affect DM intake, in sacco DM disappearance or apparent digestibility of DM or nitrogen (N), but ruminal ammonia-N and plasma urea concentrations were significantly decreased (P<0.05). In Experiment 2, 30 Friesian cows grazing mixed pasture were allocated to one of three treatments: undrenched control (C) or twice daily drenching with 90 (L) or 180 (H) ml of MB suspension (1.8 or 3.6 g CT/kg pasture DM intake) for three weeks. No significant differences in yields of milk or milk constituents were observed. Live weight and condition score changes did not differ significantly. Plasma urea concentrations were significantly lower (P<0.05) in treatment H than in treatment C. These results indicate that drenching with MB, at daily rates of 4 g CT/kg pasture DM intake, reduced ruminal protein degradation in sheep and cattle, but did not increase milk production.
Proceedings of the New Zealand Society of Animal Production, Volume 57, , 126-129, 1997
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