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 one 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 weeks of age) heifers were subject to either a High (8 L/day) or Low (4 L/day) milk feeding strategy, then at weaning either a high or 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 weeks 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 QUICKI index results were lower for heifers on the high preweaning treatment and for those on the high postweaning treatment, at 6 weeks 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 post weaning 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.