Sulfate supplementation of Alpine goats: effects on milk yield and composition, metabolites, nutrient digestibilties, and acid-base balance

K. Qi, C. D. Lu, and F. N. Owens

Effects of sulfate supplementation on milk yield and composition, ruminal and blood metabolites, acid-base status, and nutrient digestibilities were determined using 30 multiparous, lactating Alpine does. Goats were fed isonitrogenous diets containing 0.16 (basal), 0.26, or 0.36% S (DM basis) during a 13-wk lactation trial that coincided with wk 3 to 15 of lactation. During wk 16 to 17, four does from each treatment were placed in a metabolism crate to measure nutrient digestibility and balance. Feed intake, yield of 4% fat-corrected milk, and milk S content were not affected by added S, but the goats fed the 0.26% S diet had a trend of higher persistency of lactation (P < 0.20). During wk 10 and 15 of lactation, milk solids-not-fat percentage was higher (P < 0.10) for does fed the 0.26% S diet. Sulfur supplementation resulted in quadratic decreases in ruminal ammonia N (P < 0.05) in wk 15 and in plasma urea N in wk 10 and 15 (P < 0.05) but in linear increases (P < 0.05) in ruminal protein S concentrations throughout the experiment. Added S had little effect on blood acid-base status. Apparent digestibilities of DM, OM, ash, ADF, and GE were increased linearly (P < 0.10) by added S. The milk N:S ratio remained constant. Increasing S from 0.16 to 0.26% of diet DM was beneficial to lactating Alpine goats during early lactation.