127 EFFECT OF DIETARY FATS ON EMBRYO QUALITY AND YIELD IN HEAT-STRESSED DAIRY CATTLE

Abstract

The thermal environment is a major factor that can negatively affect production and reproduction of dairy cattle (Kadzere et al. 2002 Livest. Prod. Sci. 77, 59–91). Heat stress (HS) at and immediately after the time of breeding may result in a lower conception rate (Epperson and Zalesky 2007; http://wrac.sdstate.edu/pubs/ansci/ExEx2018.pdf). High temperatures compromise endometrial function and alter its secretory activity, which may lead to termination of pregnancy (Wolfenson et al. 2000 Anim. Reprod. Sci. 60–61, 535–547). One of the strategies to reduce thermal environment stress is improved nutritional management schemes like increasing dietary fat (Umphrey et al. 2001 J. Dairy Sci. 84, 2680–2685). Our objective was to determine (define) effects of protected fats on ovulation rate, embryo yield, and quality in heat-stressed Holstein cattle in Turkey. Twenty Holstein cows were assigned to control and treatment groups (86.50 ± 8.0 and 83.17 ± 10.8 DIM, respectively). Intravaginal devices (PRID) were placed in all cows (Day 0) and were superstimulated with twice-daily treatments with FSH (5, 4, 3, and 1 mL, respectively) on days 9 to 12. Also cows were treated with PgF2α (Dynolytic, 2 mL) twice on day 11. On the night of day 12, PRID were removed and animals were artificially inseminated on days 13 and 14. On day 20, inseminated cows were palpated per rectum and flushed transcervically. Following uterine flushings, each cows received PgF2α (Dynolytic, 2 mL) to induce luteolysis of developing corpora lutea. Embryos were scored and quantified, and good-quality embryos were fixed to determine embryonic cell counts. Two-twelve cell embryo and blastocyst counts were statistically different between seasons (P < 0.01 and P < 0.05, respectively); only 2-12 cell embryos were different between groups (P < 0.01) and only 2-12 cell embryos were different (P < 0.05) for season × treatment interaction. In the cool season experiment, morula and expanded blastocyst embryos were higher; and in the hot season experiment, unfertilized egg and morula embryos were higher for treatment group than those of controls. Also in the hot season experiment, total embryo yield was higher than the control group. However, dietary fats reduced rectal temperatures in these experiments. According to these results, we can assume that high rectal temperatures caused changes in blood parameters and very early embryonic deaths occurred in the control group. Consequently, dietary fats added to dairy cattle rations in hot seasons can positively affect embryo quality and embryo yield in dairy cattle.