Gonadal function arrest in fillies after birth, as reflected by steroid serum concentrations


  • Guilherme de Paula Nogueira Universidade Estadual Paulista, Faculdade de Odontologia de Araçatuba, Departamento de Apoio de Produção e Saúde Animal, Araçatuba, SP
  • Renato Campanarut Barnabe Universidade de São Paulo, Faculdade de Medicina Veterinária e Zootecnia, Departamento de Reprodução Animal, São Paulo, SP
  • Alankardson Ferreira Moreira Haras Equília, Avaré, SP
  • Ieda Terezinha do Nascimento Verreschi Universidade Federal de São Paulo, Escola Paulista de Medicina, Departamento de Endocrinologia, São Paulo, SP




Fillies, Steroids, Birth


Sexual maturation involves restraint of gonadal activity from birth to puberty, while somatic development continues. Fetal gonadal steroidogenesis is very important for the maintenance of pregnancy and foaling in mares. The present study was conducted to evaluate gonadal steroid serum levels in foals after birth. Five fillies born at Equília Stud Farm, Avaré, SP, Brazil, were studied. Blood samples were collected daily in the morning during the first week of life. Progesterone serum levels were measured by a commercial radioimmunoassay (RIA) kit and estradiol serum levels with a sensitized non-commercial RIA. At birth, both progesterone and estradiol serum levels were high (13.46 ± 5.5 nmol/l and 7.95 ± 1.5 nmol/l) and decreased to undetectable levels at the end of the first week of life. A negative correlation was found between fillie age and gonadal serum steroid concentration. Results show that fetal gonadal activity persists until birth, and decreases gradual and slowly during the first week of life, as reflected by steroid concentrations in the blood.


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How to Cite

Nogueira, G. de P., Barnabe, R. C., Moreira, A. F., & Verreschi, I. T. do N. (2000). Gonadal function arrest in fillies after birth, as reflected by steroid serum concentrations. Brazilian Journal of Veterinary Research and Animal Science, 37(4), 304-306. https://doi.org/10.1590/S1413-95962000000400008




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