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Retinol (vitamin A), alpha-tocopherol (vitamin E), and Zn are micronutrients essential for health and performance. We determined the effects of parturition, lactation, and periparturient Ca status on plasma retinol, alpha-tocopherol, and Zn in 18 Jersey cows during the 2 wk before and after parturition. Six cows developed clinical milk fever. Prepartum plasma concentrations of retinol, alpha-tocopherol, and Zn decreased progressively in all animals. A nadir was reached at 1 d postpartum when concentrations declined to 38, 47, and 67%, respectively, of prepartal baseline concentrations. Plasma Zn returned to baseline concentrations within 3 d of calving, and plasma alpha-tocopherol returned toward baseline about 10 d after calving. Plasma retinol remained below baseline concentrations throughout the first 2 wk of lactation. The decline in plasma Zn observed at calving was more severe in cows with milk fever (parturient paresis) than in cows without milk fever. The decrease in plasma retinol and alpha-tocopherol observed at parturition was similar in cows with or without milk fever. These data document an acute decline in plasma retinol, alpha-tocopherol, and Zn in the immediate periparturient period and indicate that the decline in plasma Zn is more severe in cows with milk fever.
Goff et al. (Thu,) studied this question.