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Influence of age and ovarian antral follicle count on the reproductive characteristics of embryo donor mares
  1. Gustavo Romero Goncalves1,2,
  2. Fábio Morotti1,
  3. Antonio Hugo Bezerra Colombo3,
  4. Denis Vinicius Bonato1,
  5. Camila Bizarro-Silva1,
  6. Camila Oliveira Rosa1,
  7. Fábio Luiz Bim Cavalieri3 and
  8. Marcelo Marcondes Seneda1
  1. 1 Department of Veterinary Clinics, State University of Londrina, Londrina, Parana, Brazil
  2. 2 Department of Veterinary Medicine, Inga University Center - UNINGÁ, Maringa, Parana, Brazil
  3. 3 Department of Veterinary Medicine, High Education Center of Maringa - CESUMAR, Maringa, Parana, Brazil
  1. Correspondence to Dr Marcelo Marcondes Seneda, Department of Veterinary Clinics, State University of Londrina, Londrina 86057-970, Brazil; marcelo.seneda{at}


Background Age and antral follicle count (AFC) are related to fertility in cattle, but this information remains limited in mares.

Methods To verify the influence of age and AFC on the reproductive characteristics of mares, 15 Quarter Horse donors, with 5–15 antral follicles, ranging from three to 17 years old, healthy and in good nutritional status, were divided into groups with low AFC (≤9 follicles) or high AFC (≥10 follicles) and mares considered young (≤9 years) or old (≥10 years). Mares were submitted to ultrasonography to determine the dominant follicle diameter, follicular growth rate, degree of uterine oedema and embryonic recovery for a minimum of three oestrous cycles.

Results AFC was higher (P=0.001) in young mares compared with old mares. An interaction (P=0.001) between AFC and age was observed with regard to follicular growth rate, being that mares with low AFC and are old showed the lowest follicular growth compared with those of low AFC and young, high AFC and old, and high AFC and young. Younger mares and those with high AFC exhibited higher degree of uterine oedema (P<0.05) on the third day of oestrus compared with older mares and with low AFC (3 and 2, respectively). However, in both groups, the degree of oedema reduced by the time of ovulation.

Conclusion Follicular growth rate, degree of uterine oedema and the number of antral follicles are higher in young mares with high AFC. However, the rate of embryonic recovery is not influenced by donors’ age or AFC.

  • equine
  • ovaries
  • follicular population
  • Ultrasonography
  • embryo collection
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  • Funding This study was funded by the National Council for Scientific and Technological Development (CNPq).

  • Competing interests None declared.

  • Ethics approval The experiment was approved by the ethics committee for the use of animals of the State University of Londrina (CEUA-UEL) under process number 9841.2016-52.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Data availability statement All data relevant to the study are included in the article or uploaded as supplementary information.

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