Effects of sulfate supplementation on performance, acid-base balance, and nutrient metabolism in Alpine kids

Twelve Angora goat kids (BW: mean ± SE = 18.1 + 0.6 kg; castrated males) were individually fed isonitrogenous and isocaloric diets containing 0.11 (basal), 0.20, 0.28 or 0.38% S of dietary DM (added as CaSO4). During the 8-wk growth phase, sulfate supplementation up to 0.20% S in the diet increased average daily gain (ADG) by 44%, dry matter intake (DMI) by 17%, and feed conversion efficiency (FE, ADG/DMI) by 23% compared with average Angora kids fed the other diets. Clean mohair production was numerically highest for kids fed the 0.28% S diet, but mohair fiber diameter was not affected (P > 0.20) by added S. Mohair staple length tended to increase quadratically (P 0.20) for Angora than Alpine kids. Plasma free cysteine was quadratically increased by S supplementation in Angora kids. Blood pH did not differ between breeds. Blood HCO3−, total CO2 content, pCO2, base excess in extra-cellular fluids, and standard bicarbonate were lower (P < 0.05) in Angora than in Alpine kids, but blood partial pressure of O2 and oxygen saturation were higher (P < 0.05) in Angora than in Alpine kids, perhaps due to increased heat dissipation via respiration by Angora kids. Plasma glucose, urinary outputs of creatinine and uric acid were lower (P < 0.05), and plasma free cysteine concentration higher (P < 0.01) for Angora than for Alpine kids. Ruminal l-lactate concentration (P < 0.001) and purine N content in isolated bacteria (P < 0.01) were lower, but ruminal NH3-N content (P < 0.10) was higher, and ruminal sulfide-S content (P < 0.20) tended to be higher for Angora than for Alpine kids. Angora kids were faunated, whereas Alpine kids were fauna-free. The N/S ratio in isolated rumen bacteria was lower (P < 0.10) for Angora than for Alpine kids. Calculated by regression, ADG was maximum with 0.22% S (NS = 10.4:1) for Angora kids vs. 0.21% S for Alpine kids.