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B. M. Leno, S. E. Williams, C. M. Ryan, D. Briggs, M. Crombie, T. R. Overton, 1545 Effect of peripartum source of dietary calcium and magnesium and postpartum level of magnesium on dry matter intake, performance, and plasma minerals in multiparous Holstein cows, Journal of Animal Science, Volume 94, Issue suppl_5, October 2016, Page 751, https://doi.org/10.2527/jam2016-1545
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Abstract
The objective of this study was to determine the effect of source of dietary Ca and Mg in the peripartum period and level of Mg postpartum on DMI, milk production and composition, and plasma macromineral concentrations. Multiparous Holstein cows (n = 41) were randomly assigned to one of two prepartum diets beginning at 21 d before expected parturition in which supplemental Ca and Mg were provided primarily from common sources (C; calcium carbonate and magnesium oxide) or MIN-AD (M; Papillon Agricultural Company, Inc., Easton, MD). At calving, cows remained on the same source assignment and were further randomized to receive Mg at 0.45 (C-HM, n = 11; M-HM, n = 9) or 0.30% of DM (C-LM, n = 11; M-LM, n = 10). Cows were fed individually through 42 d in milk (DIM), and blood samples were collected 2x/wk prepartum and daily from d 0 through 7 postpartum. Repeated measures data were analyzed with the MIXED procedure of SAS. Actual postpartum Mg intake, based on 21-d average DMI and diet analyses, were 84, 71, 103, and 71 g/d for C-HM, C-LM, M-HM, and M-LM, respectively. Prepartum, cows fed M had increased DMI (17.9 ± 0.3 vs. 17.0 ± 0.3 kg/d; P = 0.05) and energy balance (10.0 ± 0.4 vs. 8.7 ± 0.4 kg/d; P = 0.03). An interaction of source, level, and week was found for postpartum DMI in wk 1 to 6 (P = 0.03), reflecting increased DMI during wk 2 for cows fed M-HM. No effects on postpartum energy balance were observed. There was no effect on milk yield postpartum. A source × time interaction for fat yield (P = 0.01), 3.5% fat-corrected yield (P = 0.03), and energy-corrected yield (P = 0.02) was detected such that cows fed M had higher yield, especially in wk 1 postpartum. No effects of treatment on plasma Ca concentrations were observed. Cows fed higher Mg tended to have higher plasma Mg postpartum (1.71 ± 0.03 vs. 1.64 ± 0.03; P = 0.09) and cows fed M tended to have higher plasma P postpartum (4.67 ± 0.14 vs. 4.35 ± 0.13; P = 0.09). Overall, cows fed M had increased DMI in parts of the transition period and increased fat- and energy-corrected yield. Plasma Ca was not influenced by dietary source and level of Mg; however, plasma Mg was increased by feeding higher Mg postpartum and plasma P was increased by feeding M in the transition period.
