Effects of Different PUFAs Supplementation During the Postpartum Periods of Early Lactating Dairy Cows, I: Uterine Prostaglandin Synthesis.

The objectives were to determine if a diet enriched in a-linolenic acid (omega-3), or linolenic acid (omega-6) would influence ovarian function in lactating dairy cows. Twenty four high-yielding multiparous Holstein dairy cows with no over clinical illnesses were blocked according to calving date and parity. Cows were assigned randomly to be fed either 1-soybean whole roast (S, n=8), or 2-linseed (L, n=8), or 3-palm oil as a source of saturated fatty acid (C, n=8) from calving until first day 60 postpartum (dpp). There was no difference between groups (mean±S.E.M.) in parity (3.0±1.90) or BCS at calving (3.2±0.07). At 30 dpp, cows (n= 30) received 2 injections of PGF2a 14 d apart for estrous synchronization. On d 15 of the synchronized estrous cycle (59.3±2.6 DIM), cows were injected intravenously at 1300 h with 100 IU of oxytocin. Blood samples were collected at 15-min intervals from 1 h before until 3 h after the oxytocin injection and at 30-min intervals from 3 to 4 h post injection to monitor uterine secretion of PGF2a. Data that were repeated in time were analyzed by using a mixed model (PROC MIXED, SAS Institute Inc., Cary, NC). Result showed dietary fatty acid supplementation affected plasma PGFM concentrations in response to oxytocin injection and treatment × time interaction was significant. On the day of oxytocin challenge, the PGFM baseline for S, L and P was 16.2, 11.6 and 15.0 ng/mL (pooled SE = 1.7, P = 0.60) and the PGFM response to oxytocin 60 min after injection was 83.4, 65.1 and 109.7 ng/mL (pooled SE = 1155; P < 0.05) for P, L and S, respectively. In conclusion, these data demonstrate that Secretion of PGFM was markedly inhibited by fed linseed, but when cows treated with an increasing n-6:n-3 ratio (linoleic : EPA ratio) this inhibition was reversed.