Effect of Milk-Feeding Frequency and Calcium Gluconate Supplementation on Growth, Health, and Reproductive and Metabolic Features of Holstein Heifers at a Rearing Farm

Abstract

We compared the effects of milk-feeding in 288 Holstein calves (72 per group) which were fed twice (2F) or thrice (3F) daily, with or without the addition of hydrogenated fat-embedded calcium gluconate (G) supplemented in the starter food and in the daily diet up to the age of 9 months, on the calves’ metabolism, growth, health, and reproductive efficiency up to first pregnancy. The calves received 6 L of milk replacer (130 g/L) and had ad libitum access to water and textured calf starter with or without gluconate. Gluconate supplementation promoted a “catch-up” in growth in supplemented calves compared to their counterparts that did not receive gluconate. Gluconate appeared to reduce animal metabolic stress during key events, such as weaning and transfer into open-door pens, reducing fructosamine (352.61 vs. 303.06 in 3FG and 3F, respectively; p = 0.028) and urea (3F revealed the highest values compared with the other three groups: 19.06 for 3F vs. 13.9 (2F), 13.7 (2FG), and 14.3 (3FG), respectively, p = 0.002) from weaning onwards. The feeding of dairy calves with milk replacer three rather than two times per day tended to be associated with better health from weaning to 4 months old; parameters such as ultrasound lung score and calf health score improved over time (p < 0.001). Thrice-daily feeding with milk replacer tended to reduce the number of artificial inseminations per pregnancy in heifers by 0.2 points (p = 0.092). We confirmed significant correlations between early health and growth parameters and reproductive efficiency and a positive correlation between body weight and average daily weight gain and the thickness of the back fat layer in young heifers (r = 0.245; p < 0.0001; r = 0.214; p < 0.0001 respectively). Our study was conducted on a commercial farm with reasonably effective animal management, so baseline welfare was likely satisfactory.

Simple Summary: Female calves are the future, in terms of production, in every Holstein herd. Therefore, optimum rearing enhances productivity. Rearing dairy heifers involves important aspects of their early life that can affect their future efficiency. One of these key issues is nutrition management. Appropriate nutrition management impacts genetic performance, calf growth, and future productive and reproductive outcomes, as has been previously demonstrated in the literature. Traditionally, the recommended feeding strategies for dairy calves stipulate two daily milk replacement meals in a restricted diet. However, studies regarding feeding times point out different results in terms of efficiency, growth, and health in Holstein calves. We studied the effect of increasing feeding times (three instead of two per day) but with the same amount of milk replacer daily. Moreover, we included a supplementation of calcium gluconate to study its impact on growth, health, and productive and reproductive indexes in calves. We aimed to enhance welfare and digestive health early in life, expecting to induce positive medium- and long-term effects in the heifers. In fact, we observed a “catch-up” in the growth of calves since weaning, where supplementation with calcium gluconate appeared to reduce animal metabolic stress. We indeed observed a decreasing trend in the number of artificial inseminations per pregnancy, by 0.2 points, in heifers fed with milk replacer thrice daily. Finally, we confirmed significant correlations between early health and growth and reproductive efficiency. Although the medium- and long-term effects of these novel strategies were relatively weak, these management schemes seem to be promising for heifer rearing.