Structural and functional changes in corpus luteum of single- and/or double-ovulated pregnant and nonpregnant ewes during the spring and autumn seasons

Abstract

This study was conducted to investigate the effect of ovulation numbers on the progesterone and luteal volume in nonpregnant and pregnant Lori-Bakhtiari ewes. In the spring season 48 reproductive tracts of nonpregnant ewes (treatments included single ovulation, unilateral double ovulations, and bilateral double ovulations) and in the autumn season 144 reproductive tracts of nonpregnant and pregnant ewes (single ovulation, unilateral double ovulations, bilateral double ovulations, single ovulation with 1 foetus, single ovulation with 2 foetuses, unilateral double ovulations with 1 foetus, unilateral double ovulations with 2 foetuses, bilateral double ovulations with 1 foetus, bilateral double ovulations with 2 foetuses) were collected. The results indicated that the mean volume of the individual corpus luteum (CL) and the total volume of CL in the autumn season were significantly higher than the spring season. However, there were no significant differences in the progesterone concentration between unilateral and bilateral double ovulations. The results also indicated that in ewes with double ovulations and 1 foetus, the total volume of CL and the progesterone concentration were higher than those of the ewes with single ovulation and 1 or 2 foetuses. It was concluded that increasing the incidence of twinning rate does not appear to be a prerequisite for the presence of 2 CLs in the ewes.