Melatonin Protects Bovine Embryos from Heat Stress and Oxygen Tension and Improves Embryo Production<i> In</i><i> vitro</i>

Abstract

The objective of this study was to determine melatonin's ameliorating effects against heat stress and oxygen tension in developing bovine embryos in vitro. The oocytes were collected from ovaries obtained from a local abattoir, followed by in vitro maturation, fertilization, and embryo culture. During in vitro culture, embryos were exposed to 5% (Group I) and 20% (Group II) oxygen tension with 10(-3), 10(-6), and 10(-9) molar (M) melatonin, along with the control group without melatonin (Group III). Compared to the control group, melatonin at 10(-6) and 10(-9) concentrations increased in vitro development rates and decreased caspase 3/7 activity at 5% and 20% oxygen tension (P<0.01). Onehalf of the zygotes were cultured under normal temperature (38.5degree celsius) during the culture period, and the other half of the zygotes were heat stressed at 41degree celsius for six hours. Then they transferred into the normal culture conditions for the rest of the period using 0, 10(-6), and 10(-9) M of melatonin (Group IV). Under normal temperature (38.5degree celsius), melatonin at 10(-9) M was beneficial for in vitro development and DNA integrity. Under heat stress at 41degree celsius, melatonin at 10(-6) and 10(-9) M was useful for in vitro development and DNA integrity (P<0.05). Supplementation of melatonin to embryo culture medium did not alter the caspase 3 and 7 activities (P>0.05). In conclusion, melatonin prevents the adverse effects of heat stress and O-2 tension on preimplantation bovine embryos in vitro.