Effects of replacing sulfate with hydroxychloride sources of trace minerals on mineral status and production performance in dairy cows.
The objectives were to determine the effects of replacing sulfate with hydroxychloride sources of Cu, Mn, and Zn on mineral status and production performance in dairy cows. One hundred forty-one Holstein cows were stratified by parity group prepartum as nulliparous (lactation 0) or parous cows (lactation >0) and, within parity, cows were blocked by genomic breeding value for ECM yield (nulliparous cows) or recently completed lactation 305-d ECM (parous cows) and then randomly assigned to 1 of 2 treatments. Treatments were supplemental sources of Cu, Mn, and Zn as sulfate trace minerals (STM) or hydroxychloride trace minerals (HTM). Diets were formulated to contain approximately 16, 60, and 60 mg/kg of Cu, Mn, and Zn, respectively, and treatments were fed from 246 d of gestation to 105 d of lactation. Cows were weighed twice weekly prepartum and intake of DM, milk yield, and postpartum BW were measured daily, and composition of milk was analyzed twice weekly. Blood was sampled pre- and postpartum and hepatic tissue collected at 10 (50 STM and 52 HTM cows) and at 50 d postpartum (17 STM and 18 HTM cows) and analyzed for concentrations of minerals. Treatment did not affect intake or measures of energy balance prepartum. Numerical results between parentheses are presented following the sequence of STM and HTM. Concentrations of trace minerals in serum differed between treatments only prepartum and those of Cu (1.291 vs. 1.183 ± 0.031 mg/L) and Zn (1.307 vs. 1.211 ± 0.031 mg/L) were greater for cows fed STM compared with cows fed HTM; however, the opposite response was observed for serum Mn (1.628 vs. 1.754 ± 0.038 µg/L). Treatment did not affect liver Mn or Zn concentration, but for Cu, cows fed STM had greater concentration in the liver on d 10 postpartum compared with cows fed HTM (310 vs. 296 ± 7 mg/kg DM); however, the opposite response was observed on d 50 and cows fed STM had smaller concentration of Cu in liver than those fed HTM (287 vs. 318 ± 9 mg/kg DM). Cows fed HTM produced an additional 1.0 kg colostrum than STM cows (5.21 vs. 6.22 ± 0.63 kg), thus resulting in increased yield of colostrum solids. Treatment did not affect the content or yield of IgG in colostrum. Cows fed HTM produced 1.3 kg/d more milk (41.7 vs. 43.0 ± 0.5 kg/d) and 1.5 kg/d more energy-corrected milk (42.5 vs. 44.0 ± 0.6 kg/d) in the first 15 wk of lactation compared with cows fed STM. The estimated NEL content of the postpartum diet consumed by cows, after accounting for the different energy sinks and DMI, was 3.4% greater for HTM than STM (1.68 vs. 1.74 ± 0.02 Mcal/kg). Replacing sulfate with hydroxychloride sources of Cu, Mn, and Zn had small effects on the concentrations of those minerals in tissues and improved production performance in the first 15 wk of lactation.