effects of different level and source of sulfur supplement in close-up diets of dairy cows on blood metabolites, colostrums composition and liver performance

the 24 maltiparous holstein dairy cows were allocated in a completely randomized design to study the effects of different level and source of sulfur supplement in close-up diets on blood metabolites, colostrums composition and liver performance. the mean body weight of the cows was 687.9 kg and the mean days until expected calving date was 21.8 d. the first treatment (t1) has contained 0.21% sulfur (dm basis), the second treatment (t2) has contained 0.41% sulfur which supplied entirely through magnesium sulfate and the third treatment (t3) has contained 0.41% sulfur which supplied through a combination of magnesium sulfate and an organic source of sulfur (mepran). the dmi for pre-calving (p < 0.001) was affected by treatments and t2 showed the lowest dmi among treatments. colostrums yield, protein, dm and ash significantly decreased in inorganic sulfur supplemented treatment (p < 0.05). among the blood metabolites, calcium, copper and glucose were decreased in t2 compared with two other treatments (p < 0.05). however, bhba, nefa and urea were increased in t2 (p < 0.05). urine ph was affected with different treatments (p < 0.0001). the both liver enzymes (i.e. ast and cpk) were increased supplementing inorganic sulfur showing that inorganic sulfur has potential to decrease liver performance in dairy cows. the results of the present study indicate that although magnesium sulfate (inorganic source) has negative effect on dairy cow health and performance, a combination of magnesium sulfate and organic source of sulfur could have positive effects on dry matter intake, blood metabolites and liver health in dairy cows.