Adding sera enriched in PUFA with different n-6/n-3 ratio advanced bovine in vitro embryo development from both high- and inferior-quality oocytes
Diets containing sunflower (SUN; high linoleic acid, LA) or flaxseed (FLX; high alpha-linolenic acid, ALA) positively affect early embryonic development (EED) in dairy cows. Also, a FLX-based diet decreased the proportion of non-viable embryos in vivo. Oleic acid (OLA), abundant in canola (CAN), improves oocyte competence in vitro but its influence on EED is not known. Our objectives were to: (1) compare the effects of adding serum collected from cows fed CAN, SUN or FLX on in vitro development of bovine embryos derived from high-quality oocytes (Exp-1), and (2) determine the effect of FLX-fed-cow-serum on development of embryos derived from inferior-quality oocytes (Exp-2). Estrus-cow-serum was harvested from Holsteins fed hay (8.8 DM-kg/d) and concentrates (3.8 DM-kg/d) supplemented with 1-of-3 rolled oilseeds (8% of total DM) for ≥ 21 d: CAN (n=4); SUN (n=4); or FLX (n=4). Cumulus-oocyte-complexes (COC) aspirated from abattoir ovaries were categorized into Grade 1+2 (high-quality) and Grade 3 (inferior-quality) for Exp1 and 2, respectively. The COC were matured and fertilized (Day-0) in vitro; presumptive zygotes (n=977 from Grade 1+2, Exp-1; n=359 from Grade 3 COC, Exp-2 in 5 replicates each) were cultured with corresponding sera (5%) until Day-8. Serum fatty acid profile (% total fatty acid) were OLA 12.1, total polyunsaturated fatty acids (PUFA) 49.4, n-6/n-3ratio 4.7 (CAN); LA 52.5, PUFA 57.5, n-6/n-3ratio 10.5 (SUN); ALA 17.9, PUFA 54.3, n-6/n-3ratio 2.0 (FLX). In Exp-1, SUN (78.0) and FLX (78.8) increased (P<0.05) % cleaved compared with CAN (65.0) but not with fetal calf serum (FCS; 72.1). Blastocyst (BL) developmental rate (%) was higher (P<0.05) on Day-7 in FLX (15.5) and SUN (15.5) than in CAN (9.1) and FCS (9.2) treatments, but not on Day-8 (overall, 23.3). More (P<0.05) advanced stage embryos (expanded- and hatched-BL, %) were present on Day-8 in SUN (85.0) compared to FLX (69.8), CAN (61.5) and FCS (64.0). In Exp-2, although % cleaved did not differ (41.8), FLX tended (P=0.12) to increase BL developmental rate on Day-7 (6.73) compared to FCS (3.01). More advanced stage embryos (BL and expanded-BL) were present in FLX vs FCS (84.6 vs 0.0 %). In Exp-2, BL developmental rate (11%) and advanced stage embryos (95%) did not differ on Day-8. In summary, adding serum from cows fed FLX or SUN enhanced BL developmental rate on Day-7 and the proportion of advanced stage embryos on Day-7, even from inferior quality oocytes.
Oilseed, Embryo, Serum