A novel action of insulin sensitizing drug as a potential promotor of preovulatory follicles, ovulation rate and prolificacy in sheep: the first exploratory study

Abstract

Abstract Impact of insulin-sensitizing drug metformin on preovulatory follicle (POF) turnover, ovulation rate, and prolificacy was investigated in forty-six cyclic Malpura ewes. Following estrus synchronization, the ewes were equally divided into two groups (n = 23). Treatment group (MET) received a daily oral dose of metformin at the rate of 500 mg/animal for around 12 wk, spanning five estrous cycles, as against untreated control (CON). All the ewes were bred with proven sires at the end of treatment. Ultrasonographic ovarian scans were carried out on every estrus and D 9 of each cycle to evaluate the number and diameter of POFs and corpora lutea (CL), respectively. A comprehensive assessment was conducted on circulating hormones including, estradiol, progesterone, androstenedione, and insulin as well as metabolic indicators like glucose, and lipid profile parameters. By the end of medication, the treatment showed a stimulatory effect on follicular turnover with a 53.2% (P < 0.001) rise in the number of POFs. It further elevated the ovulation rate by 67.4% (P < 0.01), with a higher proportion (χ2df1 = 10.7, P < 0.001) of ewes in MET group having multiple ovulations compared to the CON (82.6 vs. 30.4%, respectively). The proportion of ewes delivering multiple lambs was 2.9-fold higher in MET group than the CON. The plasma estradiol, insulin, glucose, total cholesterol, and LDL-cholesterol concentrations were lower (P < 0.05) in the MET ewes than in the CON. The findings of the present study indicate that metformin can augment POF numbers, ovulation rate, and prolificacy in ewe concurrent with reduced plasma estradiol, insulin, glucose and cholesterols in MET ewes.