Management of Peripartum Dairy Cows for Metabolic Health and Immune Function
This thesis was conducted to investigate interactions among metabolic and immune system health and management of dairy cows in the peripartum period. Several management interventions recommended for the benefit of peripartum cows were explored to improve their evidence base. A randomized controlled trial evaluated the effect of a prophylactic calcium supplementation product on blood calcium concentrations, the incidence of clinical disease and culling, milk production and the probability of pregnancy at first insemination. Secondly, a study was conducted to evaluate if administration of a calcium supplement product at calving altered the immune function parameters neutrophil oxidative burst or phagocytosis capacity. Finally, a randomized controlled trial was performed to test whether reducing social stress by providing non-competitive access to feeding and lying modifies metabolic health and immune function, and if differences in metabolic health and immune function could be explained using a measure of group social status. Treatment with prophylactic subcutaneous calcium increased blood calcium levels at 24 hours after treatment and reduced the proportion of cows treated with calcium for stage 1 clinical hypocalcemia, but had no effect on the risk of other disease or culling, milk production or reproductive performance. Supplemental calcium given to low parity parturient cows did not alter oxidative burst or phagocytosis capacity of neutrophils. The calcium product may prevent visible signs of hypocalcemia in some cows but emphasize advisors must prioritize hypocalcemia prevention throughout the peripartum period. A non-competitive housing strategy modestly improved albumin and calcium concentrations during the peripartum period and improved the oxidative burst function among cows with higher social status compared to low social status cows. On average, crowding in a small, stable group through the close-up dry period without crowding or social instability in the postpartum period did not negatively affect the metabolic health and immune function of cows. As only high-rank (dominant) cows extracted an advantage from lower density housing, future research should focus on alternative strategies that better support low-rank (subordinate) cows in group housing.