Desenvolvimento gonadal fetal e análise do intraovarianismo em Bos taurus indicus

Abstract

The intraovarianism phenomenon is characterized by greater follicular activity and a greater propensity for ovulation in the right ovary compared to the left. It can directly impact reproductive biotechnologies that involve follicular dynamics. The greater propensity to ovulate in the right ovary in cattle has been known since 1916, but its origin and influencing factors are still not fully understood. There have also been reports of a higher follicle population in the right ovary of recently born calves and prepubertal heifers, indicating that this trait may develop before sexual maturity and probably before birth. Thus, we evaluated whether gonadal development and the occurrence of intraovarianism are affected by the fetal period in zebu cattle. Fifty-two fetuses were collected from slaughterhouses for biometric and ovarian follicle density evaluations. These fetuses had their gestational age estimated using body weight (kg), craniocaudal length, head width, and head length measurements and were classified into five gestational age categories: 120-150 days (10 fetuses); 150-180 days (10 fetuses); 180-210 days (16 fetuses); 210-240 days (9 fetuses) or 240-270 days (7 fetuses). Each collected ovary was identified, dissected, and measured for length, width, depth (mm), and ovarian mass (g). Ovarian samples were fixed in formalin, processed, and stained for histological evaluation. There was no significant difference in length (p=0.5515), width (p=0.7313), depth (p=0.6248), and ovarian mass (p=0.6424) between the right and left ovaries. Fetal age significantly affected all ovarian biometrics from 240 days of gestation (p<0.0001), with significant growth in both ovaries from this age. In histologic analysis, only fetuses at 180-210 days of gestation showed a higher follicle density in the right ovary (p=0.0315). The other gestational ages showed no statistical difference. Therefore, no evidence of intraovarianism was observed during the fetal period in Zebu animals, with no significant difference in ovarian biometry and follicle density between the right and left ovaries. When gonadal development was assessed, significant ovarian growth was observed during the final stages of gestation.