Impacts of feeding a fish-oil based feed supplement through 160 days in milk on reproductive and productive performance, as well as the health, of multiparous early-lactation Holstein cows

Abstract

A major cause of reproductive failure in contemporary lactating dairy cows is early post-partum negative energy balance (NEB). A strategy to alleviate NEB is to reduce milk energy density by feeding supplements to suppress milk fat synthesis, which could reduce body fat mobilization to favor earlier ovulation and improved pregnancy rates. As fish oils (FO) can cause milk fat depression, and are rich in n-3 PUFA which are beneficial to reproduction, our objective was to evaluate impacts of feeding the FO based feed supplement ‘Optomega Plus’ (OP+) on production, EB, reproduction and health of multiparous Holstein cows through ∼160 days in milk (DIM). Two pens, each of ∼310 multiparous early lactation cows, were fed rations formulated to deliver 0 (C) or 77 g/cow per day of FO (2.53 g/kg DM) as OP+, which contains 3.9 g/cow per day of eicosapentaenoic acid (EPA; C20:5 n-3) and 7.2 g/cow per day of docosahexaenoic acid (DHA; C22:6 n-3). Milk yields and components were recorded monthly for five months after cows were assigned to treatments from a common fresh cow pen at 13.3 ± 0.19 DIM, and body condition (BCS) was scored monthly on a subset of the cows. Dry matter intake (pen basis) was unaffected by treatment, while milk yield, milk components and BCS all had treatment*DIM interactions (P < 0.05), which suggested different responses to the diets before and after ∼130 days post treatment assignment. Feeding OP+ did not impact milk production, but moderately reduced (P < 0.05) milk fat output in the earlier period, which mitigated the NEB as judged by BCS change, but 1st service pregnancy rate was unaffected. There were no treatment impacts on indices of cow health, but feeding OP + improved the healthfulness of the milk FA profile to its human consumers. Results suggest that OP + as a source of FO modestly reduced milk fat output and the extent of early postpartum NEB, without negatively affecting DM intake, health or reproductive performance, while improving the nutritional value of milk fat to its human consumers.