The Effect of Dietary Manganese on Growth, Reproductive Performance, and Manganese Status of Beef Heifers
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Date
2005-10-19
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Abstract
Three trials were conducted to examine the effects of dietary manganese (Mn) on growth, reproductive performance, and Mn status of beef heifers. In Experiment 1, 80 Angus and Simmental heifers, approximately 10 mo of age, were supplemented with 0 (control), 10, 30, or 50 mg Mn/kg DM from MnSO₄ in addition to a diet containing 15.8 mg Mn/kg DM for 196 d. Performance of heifers was not affected by treatment. Liver Mn concentration increased (P=0.04) as dietary Mn level increased. Serum cholesterol was greater (P=0.001), in Angus compared to Simmental heifers for the 196-d period, but was not affected by treatment. Reproductive performance was not affected by treatment. Numerically, the number of heifers cycling at 12 mo of age, heifers bred at first service, and pregnancy rate was higher in heifers supplemented with 50 mg Mn/kg DM, compared to control heifers. In Experiment 2, 20 pregnant heifers from the control (n = 10) and 50 mg Mn/kg DM (n = 10) treatments were selected from Experiment 1 to continue on their dietary treatments through gestation and early lactation, to observe the effects of dietary Mn concentration on offspring. Serum cholesterol and whole blood Mn concentration of pregnant heifers for the 267 d study was not affected by dietary treatment. Calves born to control heifers were lighter at birth than those born to heifers receiving supplemental Mn (P = 0.02). Whole blood Mn concentration of calves at birth were lower (P = 0.01) in calves born to control heifers than those born to supplemented heifers. Seventy-one percent of calves born to control heifers exhibited some degree of superior brachygnathism.
Experiment 3 used 70 Angus and Angus-Simmental cross heifers, approximately 9 mo of age, to examine the effect of dietary Mn source and level on growth, reproductive performance, and Mn status of beef heifers. Diets consisted of a corn-silage diet (analyzed 36 mg Mn/kg DM) supplemented with 0, 30 mg Mn/kg DM from MnSO₄ (SO₄), or 30 mg Mn/kg DM from a chelated Mn source (Mn Bioplex). Performance and liver Mn concentration of heifers was not affected by source or level of dietary Mn. Serum cholesterol was affected by a treatment by breed interaction (P = 0.06), with cholesterol in Angus heifers increasing over time in response to treatment. Whole blood Mn concentration was not affected by source or concentration of dietary Mn. Dietary Mn source and concentration did not affect the percent of heifers cycling. Pregnancy rate was affected by dietary treatment (P= 0.01). Fewer SO₄ heifers were bred than control (P = 0.01) and Bioplex heifers (P = 0.04). Results suggest that a diet containing 15.8 mg Mn/kg DM is sufficient for growth of beef heifers. Supplementation of Mn to the control diet tended to improve reproductive performance and was necessary to overcome signs of Mn deficiency in the offspring of the heifers.
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Keywords
mineral nutrition, cattle
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Degree
MS
Discipline
Animal Science
