Management during the dry period and its effect on hepatic and adipose tissue molecular biomarkers of metabolism and health in grazing dairy cows
A successful transition into lactation determines optimum production, reproduction, and health. The peripartum period 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. Results 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, and the liver one-carbon metabolism and transulfuration pathway. 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 extensive analysis of the hepatic one-carbon metabolism and related pathways highlighted fundamental differences in the metabolic progression of grazing cows compared to their higher-yield counterpart in TMR-based systems. Results also indicated a greater flux through these pathways in optimally conditioned cows feed restricted prepartum. 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 negatively affected 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, results 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. As a result of the three studies, New Zealand farmers, through DairyNZ (the industry organization that represents all New Zealand dairy producers), are now discouraged to apply prophylactic pharmacological intervention early postpartum, in favour of nutritional management during the dry period. Our recommendation is for cows to be properly managed in late lactation and early dry period to attain optimal condition (e.g, BCS 5) by close-up (3 wks from calving). Subsequently cows will benefit from a controlled feed restriction (75–90% of requirements). On the other hand, cows in less than optimal condition (e.g. BCS ≤ 4) should be fed to requirements or slightly overfed (110-120% of requirements) before calving. This is an easily implementable strategy based on pasture allocation capable of benefitting the farmer with a minimum cost.
Transition cow, liver and adipose transcriptome, inflammation, prepartum nutrition
University of Illinois - Urbana-Champaign
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University of Illinois at Urbana-Champaign