Monitoring, Prevention and Treatment of Hypocalcemia in Periparturient Dairy Cows

摘要

The Ca demand of colostrum and milk production in the immediate postpartum period compared to the demands in late gestation result in a huge metabolic adaptation for periparturient dairy cows. This adaptation requires the coordination of several hormones and tissues and if delayed adaptation results in an excessive drop in blood Ca it can impair cow health and performance. Management of hypocalcemia requires multifaceted approaches that integrate prevention, treatment and monitoring. The objectives of this dissertation were to: 1) investigate strategies for monitoring blood Ca, 2) optimize application of established nutritional strategies for prevention, 3) evaluate new approaches to macromineral nutrition to support blood Ca recovery postpartum, and 3) identify opportunities for use of supplemental Ca postpartum. The VetTest is a tool that measures blood total Ca which has potential for field application and its use resulted in reliable identification of hypocalcemia. The variation in the relationship between ionized and total Ca in the immediate postpartum period suggest that these parameters cannot be used interchangeably for identification of hypocalcemia and ionized Ca was a better predictor of neutrophil function in the week postpartum. Cows fed prepartum rations with a negative DCAD, targeting an average urine pH between 5.5 and 6.0, had higher blood Ca concentrations, intake and milk production in the early lactation period compared to cows fed a low K or intermediate ration. Blood Ca responses to this preventative approach were more pronounced in cows entering their 3rd parity or greater compared to 2nd lactation cows. Altering dietary source of supplemental Ca and Mg, and postpartum dietary concentration of Mg, had minimal influence on mineral status in the transition period but did improve intake and energetic status in the transition period. This suggests opportunity for strategic use of mineral sources to support the metabolic adaptations to lactation. Supplementation with oral Ca postpartum improved early lactation health for cows with increasing age, cows with high BCS and lame cows. Plasma Ca status did not differentiate response of primiparous cows to supplementation but multiparous cows with low plasma Ca had improved health in early lactation when supplemented with oral Ca.