Effects of condensed tannins on live weight, faecal nitrogen and blood metabolites of free-ranging female goats in a semi-arid African savanna

Current understanding of the effects of condensed tannins (CTs) on productivity of mixed-feeding ruminants is largely based on simple laboratory and feeding experiments. These experiments do not allow mixed feeders such as goats to adequately employ their behavioural and physiological responses to plant secondary metabolites. In a field experiment, we investigated the effects of CTs on growth performance of goats. We hypothesized that CTs reduce blood circulatory nutrient and increase nitrogen in faeces. We divided 45 yearling females into three groups of 15 animals that were orally dosed daily with either CTs, polyethylene glycol 6000 (PEG, a polymer that neutralizes dietary tannins), or water (control). We measured the average daily gains, live weights, faecal nitrogen and four blood metabolites from each goat during dry and wet seasons. Live weights increased over time in both dry (P