J. Ivancic et Wp. Weiss, Effect of dietary sulfur and selenium concentrations on selenium balance of lactating Holstein cows, J DAIRY SCI, 84(1), 2001, pp. 225-232
The effects of dietary sulfate and selenium concentrations on selenium bala
nce in dairy cows were investigated. Midlactation Holstein cows (n = 30) we
re fed diets containing either 0.1 or 0.3 mg of supplemental Se (from sodiu
m selenate)/kg of dry matter and 0, 0.2, or 0.4% added S from a mix of calc
ium and magnesium sulfate in a factorial arrangement. The experiment lasted
112 d. Dry matter intake was linearly reduced with increasing S, but the e
ffect was greater when 0.3 mg/kg of Se was fed (significant interaction). T
reatment effects for yields of milk, milk fat, and milk protein were simila
r to those for dry matter intake. Increased dietary S linearly reduced plas
ma Se concentrations. Increasing dietary S linearly reduced apparent (42.7,
33.1, and 30.1%) and estimated true (50.5, 46.0, and 42.3%) Se digestibili
ty. Excretion of Se via feces (1.6 vs. 2.8 mg/d) and urine (0.5 vs. 1.3 mg/
d) was higher and output in milk (0.4 vs. 0.3 mg/d) was lower for cows fed
0.3 mg/kg of Se compared with 0.1 mg/kg, but no Se effect was found for est
imated true Se digestibility. Dietary S from sulfate reduced Se balance esp
ecially when cows were fed diets with less than 0.3 mg of Se/kg of diet dry
matter.