The Preservation of the Effects of Preweaning Nutrition on Growth, Immune Competence and Metabolic Characteristics of the Developing Heifer

SIMPLE SUMMARY: This experiment is the postweaning phase of a series of experiments following 20 dairy replacement heifers from birth through to 22 months of age. During the preweaning phase (outlined in a companion paper), calves fed a high volume of milk (8 L per day) had superior growth, immune competence and metabolic characteristics when faced with a vaccination immune challenge than those on a lower volume of milk (4 L per day). Postweaning, these calves were treated equally under non-experimental conditions, and these systems were re-examined with a repeat immune challenge at 12 months of age (current experiment). Findings from this immune challenge suggest immunological imprinting from the preweaning nutrition. Superior immune responses were found in the heifers fed high volumes of milk in the preweaning phase, despite a period of 9 months of no nutritional treatment. Despite the greater immune response, there was no difference in the metabolic biomarkers detected between the two preweaning treatment groups, suggesting no trade off or compensation of energy to other processes for this superior response. Accelerated growth from the low treatment group resulted in no differences in bodyweight between the treatment groups at 13 months of age. The results indicate a positive influence for improved preweaning nutrition on heifer immune response until at least 12 months of age. ABSTRACT: This experiment investigated the preservation effects of two preweaning milk feeding nutritional treatments (High: 8 L and Low: 4 L milk per day) on 20, 12-month-old Holstein-Friesian dairy heifers (Bos taurus). A vaccination immune challenge was initially implemented on these 20 heifers at 6 weeks of age and the findings indicated superior growth, immune competence and favorable metabolic characteristics from the calves that had been fed 8 L milk per day. Postweaning, all heifers were treated the same under non-experimental conditions, and the immune challenge was repeated at 12 months of age for the current experiment. Consistent with the first immune challenge, heifers from the High preweaning treatment group still had higher white cell count and neutrophil count, indicating superior immune competence. The differences found in metabolic biomarkers, including beta-hydroxybutyrate, glucose and insulin, in the preweaning phase had disappeared, suggesting these biomarkers were influenced directly by the nutritional input at the time. There were no differences in NEFA levels between treatments at either stage of development. Postweaning, the heifers from the Low preweaning treatment group experienced accelerated growth with slightly numerically higher ADG (0.83 kg/day vs. 0.89 kg/day), resulting in the initial differences in bodyweight recorded at weaning being eliminated by 13 months of age. These results are evidence of a form of immunological developmental programming as a result of accelerated preweaning nutrition and therefore, are not supportive of restricted milk feeding of calves.