Goat supplementation in dry tropical agroforestry: assessment of methodologies for estimation of nutrient intake

Abstract

Forage intake by grazing ruminants cannot be measured directly, which requires specific methodologies for its estimation, that generally involve the use of markers. The purpose of this study was to test methodologies for estimating dry matter intake (DMI) in supplemented grazing goats in dry tropical agroforestry (Caatinga). It was used eight esophagus-fistulated animals grazing in the semi-arid region, and receiving concentrate-based supplementation (0, 0.5, 1.0 and 1.5% based on body weight, BW). The methods used to estimate intake were: ingestive behavior (IB), in vitro dry matter digestibility (IVDMD) and indigestible acid detergent fiber (iADF). The data was subjected to joint analysis of variance, analysis of variance and regression (regression analysis only for the effect of supplementation). The average DMI values obtained using the estimation methods were subjected to mean comparison tests. The estimates of total DMI in relation to BW using IB, IVDMD and iADF methods were 1.47, 3.21 and 2.96% of BW, respectively. Forage intake obtained through IB and IVDMD methods was not affected by the increase in supplementation levels, showing average values of 143.5 and 513.6 g DM/day, respectively. Method IB underestimated DMI in comparison to IVDMD. in vitro dry matter digestibility and indigestible acid detergent fiber methods are suitable for estimating DM intake of goats in dry tropical agroforestry.