The anthelmintic effect of heather supplementation may not always be associated with antinutritional effects in grazing goats
2009
Frutos, P. | Hervás G. | Ferreira, L.M.M. | García, U. | Celaya, R. | Osoro, K. | Moreno-Gonzalo, J. | Ferre, I. | Ortega-Mora, L.M.
To test the hypothesis that the beneficial anthelmintic effect of the consumption of moderate amounts of tannins is not always accompanied by anti-nutritional effects, we used 48 Cashmere goats randomly assigned to 2 treatments (supplemented with heather (6.4 per cent total tannins) vs non-supplemented). All goats grazed continuously from May to September, under practical conditions in a mountain area of Northern Spain. Heather percentage in the diet of supplemented animals reached 29.1 per cent. Supplementation with heather reduced the mean number of nematode eggs in faeces and the mortality rate (at the end of the grazing period, 2 goats had died in the group supplemented with heather vs 8 in the group without supplementation). Rumen ammonia concentration was markedly decreased in goats receiving tannin-containing heather, which agrees with the well known effect of tannins on the proteolysis of feed protein. On the contrary, volatile fatty acid (VFA) concentrations were significantly greater in supplemented animals due mainly to acetic and propionic acid increases, in spite of valeric and branched-VFA decreases, which suggests that ruminal fermentation was not adversely affected by tannin consumption. These data, together with a lower loss of live weight and body condition score in heather supplemented goats, support the absence of any apparent nutritional cost that counteracted the beneficial anthelmintic effect of the supplementation of grazing goats with tannin-containing heather
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