The effects of condensed tannins supplementation of foods with different protein content on parasitism, food intake and performance of sheep infected with Trichostrongylus colubriformis

The aims of the present study were to investigate (1), the potential anthelmintic properties and (2), the nutritional consequences of commercially available condensed tannins on parasitised sheep fed, ad libitum, either a high- or a low-protein food. For this purpose, forty-eight previously parasite-naive sheep (n 12) were infected with 2000 Trichostrongylus colubriformis larvae/d for a 67-d experimental period. Two experimental foods were made: a low (L), formulated to be inadequate in meeting the requirements of growing sheep for metabolisable protein (MP), and based on wheat, citrus pulp, and oatfeed; a high (H), expected to be above the requirements of growing sheep for MP, based on similar ingredients but supplemented with protected soyabean meal. Two additional foods were made by adding 60 g Quebracho (a condensed tannins (CT) extract)/kg fresh matter to foods L and H (foods LQ and HQ respectively). This level of Quebracho supplementation has been previously shown to reduce the level of parasitism in restrictedly fed, parasitised sheep. The experiment was divided into two periods: period 1 (P-1, day 1-38) and period 2 (P-2, day 39-67), each one associated with different phases of an intestinal parasitic infection. Six sheep from each group were slaughtered at the end of P-1, and the remaining sheep were slaughtered at the end of P-2 (day 67). Although faecal egg counts (FEC; number of parasite eggs/g faeces) and total egg output were reduced in sheep offered the supplemented foods during P-1 (P<0.05), worm burdens on day 38 were unaltered. Neither Quebracho supplementation nor food protein content during P-2 affected FEC and worm burdens. Food intake and performance were higher in sheep offered food HQ compared with sheep offered food H (P<0.05); no differences were observed in sheep offered foods LQ and L throughout the experiment. The previously shown anthelmintic properties of CT were not observed following ad libitum intake of either low- or high-protein foods supplemented with Quebracho extract. Higher levels of CT supplementation may be required to reduce parasitism and consequently improve the performance of parasitised sheep, when fed ad libitum. Supplementation with CT conferred advantages on the performance of parasitised sheep on a high- but not on a low-protein food.