Effects of Acacia mearnsii extract as a condensed-tannin source on animal performance, carcass yield and meat quality in goats

Abstract

The objective of this study was to determine the optimum level of condensed tannins (CTs), delivered as Acacia mearnsii extract, for inclusion in the diet of goats for enhancing growth, commercial cuts, the physicochemical composition and fatty acid (FA) profile of the meat and meat sensory attributes. Thirty-two castrated crossbreed Boer goats with a mean age of four months and a mean body weight (BW) of 19.7 ± 2.05 kg were distributed in a completely randomized design. The diets varied in level of CTs [0, 16, 32 and 48 g/kg dry matter (DM)] from an Acacia mearnsii extract. Final BW; acid detergent fiber (ADF); shoulder, neck and rib weight; and loin yield increased quadratically (P ≤ 0.05) with the amount of CTs in the diet. Except for a trend of a quadratic reduction in luminosity color (P = 0.07) and a linear reduction in collagen deposition (P = 0.03) with increasing level of dietary CTs, the meat physicochemical parameters were unaffected by CTs inclusion. With increasing amount of CTs from Acacia mearnsii extract in the diet, the concentrations of C17:1 and C18:1 cis-9 in the longissimus lumborum of goats linearly decreased, whereas those of C18:0, C18:2 cis-9, cis-12 and C18:3 cis-9, cis-12, cis-15 (P ≤ 0.05) linearly increased. In addition, the values of total saturated FA (ΣSFA), polyunsaturated FA (ΣPUFA), ratio of ΣPUFA:ΣSFA and ΣPUFA:monounsaturated FA (ΣMUFA) increased (P ≤ 0.05) with increasing CTs level; in contrast, ΣMUFA and the ΣMUFA/ΣSFA ratio decreased. Other FA sums and ratios were not affected by the inclusion of CTs in the diet. The inclusion of dietary CTs tended to unfavorably reduce the FA index and enzymatic activity of Δ9-desaturase C16 (P ≤ 0.10). However, there was a linear decrease (P ≤ 0.05) in Δ9-desaturase C18 and elongase enzymatic activities and the hypocholesterolemic to hypercholesterolemic FA ratio (h:H) index with increasing level of dietary CTs, and the atherogenicity index (AI) tended to increase as the CTs level increased (P = 0.06). The dietary inclusion of the Acacia mearnsii extract improved the flavor, aroma, softness and overall acceptance of goat kid meat (P ≤ 0.05). Linear response plateau (LRP) analysis demonstrated that Acacia mearnsii levels of 16 and 32 g/kg DM had similar effects and increased growth performance and carcass cut weights (P < 0.05). The inclusion of CTs from Acacia mearnsii extract at 16 and 32 g/kg DM in goat kid diets is recommended because it increases goat growth performance, the commercial cut weights and ∑PUFA contents of the meat and meat sensory attributes.