Effect of Diet Supplementation with Omega-3 Fatty Acids on Reproduction and Milk Production in Cattle

Abstract The aim was to assess the effects of omega-3 fatty acid supplementation on reproduction and milk production in cattle. Holstein cows (primiparous; n = 22], multiparous; n = 28) housed at the Kansas State University dairy were randomly assigned to two diets: omega-6:omega-3 ratio of 6:1 (Control, n = 26), or 2:1 (OMG3, n = 24), and allocated randomly into 6 pens (3 controls and 3 OMG3). Diets were isocaloric and isonitrogenous. GreatOPlus, which is an extruded feed containing flaxseed and Nannochloropsis oculata algae, was used in OMG3. Cows were milked 3x/d, and fed fed experimental diets from 15 days in milk (DIM) until ~140 DIM 1x/d. Data were analyzed using the Glimmix procedure (SAS 9.4). Body condition score was not different (P = 0.15) between Controls and OMG3 diets at –21, 0, 21, 50, 75, or 110 DIM. Multiparous OMG3 cows (60.8 ± 2.2 kg) tended (P = 0.1) to produce more milk (15 to 140 DIM) than multiparous Controls (55.6 ± 2.2 kg). Primiparous (41.5±1.7 kg) produced less (P < 0.01) milk than multiparous, with no difference between diets. Based on milk and blood samples from 15, 50, 75, and 110 DIM, milk protein (2.84 ± 0.34%) and fat (3.27 ± 1.08%) were not different between diets (P > 0.45), but plasma ratio omega-6:omega-3 was reduced (P < 0.001) in the OMG3 at 50, 75, and 110 DIM compared with Controls. Thus, hypothesis 1 was supported, that OMG3 would not influence milk protein or fat content but would have greater omega-3 concentration. Oocyte quality was assessed by a single oocyte harvest at 50 DIM, and number of follicles (> 3 mm) or recovered oocytes did not differ between diets (P > 0.3), but a diet-by-parity interaction was detected (P = 0.0007) for the number of grade I and II oocytes/total recovered oocytes: primiparous-Controls = 58.5 ± 8.6%; multiparous-Controls = 59.7 ± 7.9%; primiparous-OMG3 = 31.2 ± 7.8%; multiparous-OMG3 = 70.5 ± 7.5%. Cows received first and second TAI at 75 and 110 DIM, respectively, and weekly ovarian ultrasound was performed from day 11 post-TAI until day 30 to evaluate CL volume and blood flow. On day 30 post-TAI, pregnancy was diagnosed by an embryo with heartbeat. From days 30 to 60 post-TAI, pregnant cows had CL, embryo, and amniotic vesicle evaluations. Only pregnant primiparous-Controls (n = 6), primiparous-OMG3 (n = 7), and multiparous-Controls (n = 9) were compared post-TAI due to lack of representation in the multiparous-OMG3. CL volume did not differ (P > 0.3) among groups, but CL blood flow was less in primiparous-Controls on days 25 and 39 post-TAI. Finally, embryo and vesicle size did not differ among groups (P > 0.7). Thus, hypothesis 2 was partially supported, that omega-3 enhances oocyte quality and in vivo embryo development. In conclusion, omega-3 supplementation increases omega-3 in blood and enhanced oocyte and CL quality, but it is unclear if this can translate into direct benefits on embryos from day 30 to 60 of gestation.