Effect of Supplemental Dietary Vitamin E and Zinc on Reproductive Performance of Dairy Cows and Heifers Fed Excess Iron

¹ Department of Animal Science, The University of Tennessee, Knoxville 37996

We tested the hypothesis that the incidence of retained fetal membranes could be reduced by limiting oxidative stress. Sixty-four primigravid heifers (56 Holstein and 8 Jersey) and 80 multiparous cows (64 Holstein and 16 Jersey) were used. A combination of vitamin E or Zn and Fe was fed in a 2 x 2 x 2 factorial arrangement during the last 42 d prepartum. Amounts of supplements per animal were 1000 IU of vitamin E (d,l -tocopheryl acetate), 0.8 g of Zn (Zn-Met and ZnSO₄), and 12 g of Fe (FeSO₄·7H₂O) for Holsteins and 9 g for Jerseys. Neither vitamin E nor Zn directly affected the incidence of retained fetal membranes, but plasma -tocopherol was lower when fetal membranes were retained >12 h or when vitamin E was not supplemented. Iron had no direct negative effects on reproductive performance, but cows receiving additional Fe had lower unsaturated iron-binding capacity, which, in turn, was also lower in cows that retained fetal membranes. Days to first observed estrus were reduced by supplementation with either vitamin E or Zn. Vitamin E reduced days to first artificial insemination (AI) and tended to reduce days open. Supplemental Zn tended to reduce days to first AI but did not affect days open. Milk production during the first 12 wk and AI per conception were not affected by supplementation with either vitamin E or Zn. Both vitamin E and Zn reduced days to first observed estrus, indicating improved reproductive health during the early postpartum period.

Key Words: dairy cows • reproduction • estrus detection • antioxidants

Submitted on March 2, 1998
Accepted on July 20, 1998

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