In vivo use of melatonin improves oocyte developmental competence and blastocyst development rate in indigenous donor...

In summer, bovine fertility may be reduced by increased ambient temperatures which may adversely affect the developmental competence of oocytes. This study aimed to determine how in vivo melatonin treatment affected blastocyst development rates and expression profiles of genes involved in oocyte and blastocyst development in indigenous cows during summer. The non-lactating indigenous Sahiwal cows were divided into treatment (n = 25) and control (n = 19) groups. On Day 0, the treatment group received melatonin @ 18 mg/50 kg body weight, while the control group received 4 mL placebo (corn oil) intramuscularly. All cows were subjected to ovum pickup on Day 4 for blastocyst development in vitro. Results showed that the treatment group had a higher (P < 0.04) blastocyst development rate (38.41 vs. 25.29%) than the control group. Melatonin improved mRNA expression levels of SOD2, HSPB1, BCL2, MT2 and STAR in oocytes, cumulus cells, COCs (immature and mature), and blastocysts, while reducing BAX expression levels compared to the control group. In addition, mRNA expression of ADAMTS remained comparable between the treated and control groups. In conclusion, in vivo administration of melatonin enhanced the antioxidant, anti-apoptotic and steroidogenic effects of oocytes and blastocysts in indigenous cattle during summer, which in turn increased blastocyst development rate and oocyte developmental competence.