Two- year- old Holstein Friesian dairy cows (n=20) were allocated to receive either a rumen- protected fish oil supplement (omega group, n=10), starting between 5-6 weeks post-partum, or pasture only (control group, n=10). .Serum metabolites, including cholesterol, urea, glucose and beta-hydroxybutyrate (BOH) were measured weekly from calving through to week 11-12 post-partum. Within 2 weeks of the commencement of treatment, serum cholesterol concentrations had increased significantly in the omega group vs the control group, and continued to increase through to weeks 11-12 post-partum. None of the other serum metabolites measured showed any differences with treatment. However, levels of serum urea, BOH and plasma glucose showed significant variations from week to week . The size of the dominant follicles and corpus luteum were measured, using transrectal ultrasonography, on days 8 to 16 of both oestrous cycles. The corpus luteum of the second cycle was significantly larger in the omega group. The second oestrous cycle was interrupted through an oxytocin challenge carried out to measure prostaglandin synthesis, on day 16 of the cycle. After the oxytocin challenge, the omega group exhibited a longer interval to the next observed oestrus. These results suggest that supplementing dairy cows with 3-omega fatty acids will result in changes at the site of the ovary and uterus.

S, Meier

Proceedings of the New Zealand Society of Animal Production, Volume 60, Hamilton, 297-300, 2000
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