Productive performance, rumen volatile fatty acid profile and plasma metabolites of concentrate-supplemented Bach Thao goats in Vietnam

Twenty-five Bach Thao bucks (7 months old and 20.9±0.3 kg BW) were used to quantify the effect of concentrate supplementation on growth performance, rumen volatile fatty acid profile, digestibility and plasma metabolites. Goats were allocated into five treatment groups of varying levels of concentrate supplementation: Control (ad libitum access to elephant grass), 0.6% C (control plus 0.6% of concentrates), 1.2% C (control plus 1.2% of Concentrates), 1.8% C (control plus 1.8% of Concentrates) and 2.4% C (control plus 2.4% of Concentrates) as a percentage of liveweight on a dry matter basis. Growth and feed intake were measured in a 6 week feeding trial period after 3 week of initial adaptation. In vivo digestibility was assessed in the 10th week by the total faecal collection method. There were significant increases in average daily gain (ADG), feed intake and digestibilities of dry matter (DM), organic matter (OM) and crude protein (CP) as dietary concentrate levels increased. However, digestibility of neutral detergent fibre (NDF) was not different between the concentrate-supplemented groups. Pre-feeding ammonia concentration in rumen fluid was not different between treatments, but 4hrs after feeding, significant differences were detected. The values of ammonia ranged from 100-200 mg L⁻¹ at both times of measurement. Rumen fluid pH values were not different 4hrs post-feeding. Volatile fatty acid concentrations of propionate and butyrate increased with increasing levels of concentrates consumed, in contrast to decreased acetate concentration. This study clearly demonstrated that increasing concentrate levels offered to Bach Thao bucks up to 1.8% of live weight on a DM basis resulted in the greatest improvement in ADG, feed intake and nutrient digestibility, thus, confirming the tested hypothesis that increased level of concentrate supplementation will improve productive performance of goats without an adverse effect on rumen fermentation and nutrient digestibility.