The effect of a bypass n-3 fatty-acid supplementation on the reproductive resumption in dairy cows after calving

This study evaluated the effects of the n-3 fatty-acid supplementation on a reproductive and productive performance of dairy cattle, focusing on a successful early insemination. A total of 61 cows were assigned to either the control (control, n = 31) or Hi-Flax (HF, n = 30) group on a commercial farm located in Normandy (Manche, France). Both groups received the same basal diet, and the animals in the HF group were supplemented with 250 g/day rumen protected source of n-3 fatty acids during the first 55 days of lactation. The productive parameters included the milk yield, fat, and protein content, feed intake time, and rumination time during the first 100 days of lactation. The reproductive parameters analyzed were as follows: calving interval (i.e., the intervals from calving to first estrus), first AI, and a successful AI; the number of AIs, and the fertility at the first AI. The ANOVA and the linear mixed models were applied for the productive traits, with a treatment, parity, and days in milk as the fixed effects, and cow as a random effect. The reproductive parameters were analyzed using the linear and the generalized linear mixed models, assuming a binomial distribution for fertility. The results indicated no significant differences in a productive performance. However, the HF group had reduced the intervals from calving to the first AI (-24 days, 18%, p = 0.06) and a successful AI (-31.94 days, 19%, p = 0.01), leading to a shorter calving interval (-31.94 days, 7%, p = 0.02). These findings showed that the supplementation with a rumen-protected source of n-3 fatty acids improved a reproductive performance in dairy cattle, with a subsequent reduction of non-productive periods. The results highlighted a beneficial impact on the resumption to a reproductive activity, with a reduction of an interval from calving to the first estrous (heat), an earlier first successful artificial insemination, and a resulting calving-interval decrease.