Effects of supplementing complexed zinc, manganese, copper and cobalt on lactation and reproductive performance of intensively grazed lactating dairy cattle on the South Island of New Zealand

Abstract

Five hundred and fifty-five healthy, pregnant, non-lactating Holstein–Friesian cows on an intensively grazed, commercial dairy were assigned to a study to determine effects of daily water treatment with Co glucoheptonate and amino acid complexes of Zn, Mn and Cu on lactational performance, fertility and claw hardness. Cows were randomly assigned to treatment based upon eartag number. At approximately 35 days prior to calving, cows began receiving either a diet containing no supplemental Zn, Mn, Cu and Co or a diet which provided daily 360 mg Zn, 200 mg Mn, 125 mg Cu and 12 mg Co from complexed sources (CTM). Cows continued to receive their respective treatments through 230 days postpartum. Treatments were delivered via a commercial concentrate, precalving and postcalving, by dispersing CTM (liquid) into water troughs. Cows were milked twice daily, milk weights were recorded and samples collected six times during lactation. All reproductive events were recorded. Claws were examined on four separate occasions with liver and blood samples collected on three separate occasions during the study. Compared to the control, supplementing CTM increased (P≤0.05) yield of milk (17.5 kg/day versus 16.6 kg/day), milk energy (58.6 MJ/day versus 55.3 MJ/day), milk fat (0.78 kg/day versus 0.73 kg/day), milk crude protein (0.62 kg/day versus 0.58 kg/day) and milk solids (1.39 kg/day versus 1.31 kg/day). There was no effect of treatment on milk composition or somatic cell content of milk. Supplementing CTM reduced (P≤0.05) controlled internal drug releasing usage (16 cases/100 cows versus 26 cases/100 cows) and tended (P≤0.10) to reduce incidence of non-pregnant cows (13 cases/100 cows versus 18 cases/100 cows) and mastitis cases (23.8 cases/100 cows versus 29.9 cases/100 cows). Supplementing CTM increased Cu and Vitamin B 12 status (P≤0.05) as indicated by liver Cu and serum Vitamin B 12 content. There was no effect of treatment on claw hardness. Increasing Zn, Mn, Cu and Co intake of intensely grazed dairy cattle through CTM supplementation increased lactation performance, fertility and Cu and Vitamin B 12 reserves.