Early-life nutrition and its effects on the developing heifer: Growth, nutritive intakes, and metabolism

We aimed to assess the effects of preweaning nutrition and postweaning growth rates on the metabolic characteristics of replacement dairy heifers until 20 mo of age. At birth, heifers were allocated to 1 of 4 treatment groups, which were a combination of preweaning (high or low preweaning nutritional treatment) and postweaning treatments (high or low postweaning growth rate). In the preweaning phase (birth until weaning at 10 wk of age), heifers were subject to either a high (8 L/d) or a low (4 L/d) milk feeding strategy; then, at weaning, either a high or a low postweaning growth rate. Heifers in the high preweaning treatment groups recorded greater growth rates until weaning compared with heifers in the low preweaning treatment groups. Heifers in the high preweaning groups consumed approximately twice the amount of milk and half the amount of concentrate. Blood samples taken at 6 wk of age had lower BHB and higher glucose and IGF-1 concentrations in the high preweaning treatment in the preweaning phase; these differences disappeared postweaning. Additionally, insulin levels were also higher, and quantitative insulin sensitivity check index (QUICKI) results were lower for heifers on the high preweaning treatment and for those on the high postweaning treatment at 6 wk and 13 mo of age. No differences between treatments were detected at 8 mo of age. Results indicate a positive effect of accelerated preweaning nutrition and postweaning growth rate (at 13 mo of age) on these metabolic biomarkers; however, these treatment effects were independent of one another and reflected the nutritional input at the time.