Diets enriched in unsaturated fatty acids enhance early embryonic development in lactating Holstein cows

We hypothesized that a diet enriched in α-linolenic acid would enhance embryonic development relative to diets enriched in linoleic or saturated fatty acids. Twenty-four lactating Holstein cows (86 ± 22 d postpartum) were assigned to one of three diets containing saturated fatty acids (SAT; high in palmitic and stearic acids), whole flaxseed (FLX; high in α-linolenic acid) or sunflower seed (SUN; high in linoleic acid). Rations were formulated to provide 750 g supplemental fat/cow/d in all dietary groups. Ovulation (Day 0) was synchronized approximately 20 d after diets began. Ultrasound-guided follicular ablation of all follicles >8 mm was performed 5 d after ovulation; superstimulatory treatments began 2 d after follicular ablation, and embryos were collected non-surgically 7 d after AI. Fertilization rate, numbers of follicles and ovulations, and total and transferable embryos did not differ (P > 0.05) among dietary groups. Sixty-one transferable embryos were stained and total blastomere number determined. Blastomere number was affected by diet (P < 0.01); without regard to stage of development, embryos collected from cows fed SAT had lower (P < 0.01) blastomere numbers (mean ± S.E.M.; 77.1 ± 3.9) than those from cows fed FLX (93.4 ± 3.3) or SUN (97.2 ± 3.5). Differences were most evident in the expanded blastocyst stage; at this stage, embryos of cows fed FLX and SUN diets had more blastomeres (P < 0.02) than those of cows fed SAT (115.4 ± 6.3, 132.3 ± 8.3, and 89.3 ± 9.6 cells, respectively). Although our hypothesis was only partially supported, embryonic development was enhanced in Holstein cows fed unsaturated fatty acids compared to those fed saturated fatty acids.