Journal of Dairy Science 2018-03-28

Interaction of 5-hydroxy-l-tryptophan and negative dietary cation-anion difference on calcium homeostasis in multiparous peripartum dairy cows

C.J. Slater, E.L. Endres, S.R. Weaver, A.A. Cheng, M.R. Lauber, S.F. Endres, E. Olstad, A. DeBruin, P.M. Crump, E. Block, L.L. Hernandez

文献索引：10.3168/jds.2017-13938

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摘要

Hypocalcemia affects almost 50% of all dairy cows. Our laboratory has previously demonstrated that infusions of the serotonin precursor 5-hydroxy-l-tryptophan (5-HTP) increase circulating calcium concentrations in the Holstein transition cow. It is unknown whether feeding a negative DCAD diet alters the relationship between 5-HTP and hypocalcemia. The main objective of this study was to determine whether feeding a negative dietary cation-anion difference (−DCAD) diet before calving in conjunction with 5-HTP treatment could further diminish the magnitude of hypocalcemia at the time of calving. We used a randomized complete block design with a 2 × 2 factorial arrangement. Thirty-one multiparous Holstein cows were fed either a positive (+13 mEq/100 g) or negative (−13 mEq/100 g) DCAD diet 21 d before parturition and were intravenously infused daily with saline or 5-HTP (1 mg/kg) starting 7 d before the estimated date of parturition. Cows were blocked by parity and were randomly assigned to 1 of 4 treatment groups: positive DCAD plus saline, positive DCAD plus 5-HTP, negative DCAD plus saline, and negative DCAD plus 5-HTP, resulting in n = 8 per group. Total calcium (tCa), ionized calcium (iCa), and feed intake were recorded. The iCa was elevated prepartum in the −DCAD/5-HTP group compared with the other treatment groups as well as on d 0 and 1 postpartum. Although differences in tCa were not significant across the pre- or postpartum periods, tCa was numerically higher on d 0 and significantly higher on d 1 in −DCAD/5-HTP cows compared with all other groups. Prepartum the −DCAD/5-HTP treatment group ate less than the other treatment groups; however, postpartum dry matter intake differences were not significant. These findings demonstrate that feeding a −DCAD diet in conjunction with 5-HTP prepartum can increase postpartum circulating iCa concentrations and therefore diminish the magnitude of hypocalcemia at the time of parturition.