Young Scholar Presentation: Immuno-Metabolic Adaptations to Lactation in Pasture-Based Transition Dairy Cows Can be Regulated By Prepartum Nutritional Strategies

A successful transition into lactation determines optimum production, reproduction, and health. The peripartum is characterized by an inflammatory state that, if not controlled, could be detrimental to the cow. The first experiment examined hepatic and adipose gene expression in response to injections of a non-steroidal anti-inflammatory compound (Carprofen) on 1, 3, and 5 d postpartum. Data indicated that after calving both tissues respond to inflammation signals, underscoring its role in the normal homeorhetic adaptations to lactation. The second experiment investigated the effect of prepartal nutrition and its interaction with BCS on hepatic and adipose tissue transcriptome. Cows were randomly allocated to one of four groups in a 2 × 2 factorial arrangement: 4.0 or 5.0 BCS prepartum (10-point scale) and dietary energy at 75 or 125% of estimated requirements during the close-up. Tissue biopsies were harvested at -1, 1 and 4 wk relative to parturition. The greater number of hepatic differentially expressed genes in BCS4 cows in response to increased prepartum feed allowance (1071 vs 310, over the entire transition period) indicated a greater responsiveness to prepartum nutrition than optimally-conditioned cows. Thus, overfeeding in late-pregnancy should be limited to underconditioned cows, while cows with optimal BCS should be maintained on an energy-restricted diet. Adipose tissue mRNA and microRNA expression further confirmed this hypothesis, and indicated a relationship between the immune and metabolic response of the adipose tissue underscoring the existence of a “self-regulatory” mechanism. The third experiment examined the effect of over-feeding in both close-up and far-off periods on the adipose tissue transcriptome. Far-off over-feeding is usually a standard practice in seasonal grazing systems as, compared with TMR-fed cows, cows are thinner at the end of lactation. Adipose expression data revealed how overfed cows in the far-off period had greater adipogenesis, consistent with their rapid gain in BCS following dry-off, but a lower body fat mobilization in early lactation. The results indicated that neither strategy affected negatively the adaptations to lactation. However, to ensure a favorable transition, cows should be subjected to a small feed restriction in the close-up period, irrespective of far-off nutrition. Overall, data indicated a beneficial involvement of the immune system in the adaptation to lactation, and the possibility to regulate this process through prepartal BCS and nutrition management.