Relationships between antral follicle count and embryo transfer

Relationships between antral follicle count and reproductive characteristics of embryo-recipient mares

J Equine Vet Sci. 2024 Feb 10:105029. doi: 10.1016/j.jevs.2024.105029. Online ahead of print.
Authors
Sofia Botsaris Delchiaro 1 , Pedro Victor de Luna Freire Oliveira 2 , Rubens José Paulossi Júnior 3 , Gabrieli Dutra Gonçalves 3 , Fábio Morotti 3 , Marcelo Marcondes Seneda 3
Affiliations

1 State University of Londrina (UEL), Highway Celso Garcia Cid, PR-445, Km 380 – Campus Universitário, Londrina, PR, 86057-970. Electronic address: sofiabdelchiaro@gmail.com.
2 Philadelphia University Center (UniFil), Street Alagoas, 2050 – Centro, Londrina, PR, 86010-520.
3 State University of Londrina (UEL), Highway Celso Garcia Cid, PR-445, Km 380 – Campus Universitário, Londrina, PR, 86057-970.

PMID: 38346582
DOI: 10.1016/j.jevs.2024.105029

Abstract

Mares (n=77) were evaluated by antral follicle count (AFC) and selected as embryo recipients. Cyclic recipients received embryos between days 4-6 after ovulation. The acyclic recipients received an intramuscular (i.m.) protocol with 5mg of estradiol benzoate (EB) on the day of donor ovulation (D0; D-4 recipient), 3mg of EB on the following day (D1; D-3 recipient), and 3mg of EB (D2; D-2 recipient). Furthermore, 1500mg of progesterone (P4) i.m. given on D0 of the recipient (D4 donor) followed by 1500mg of P4 on the day of ET (D4-6 recipient). On the ET day, the AFC and animals’ weight, body condition score (BCS), corpus luteum diameter, age and degree of uterine edema (UE) were measured. Pregnancy was confirmed on days 12 and 30. Low AFC was defined as ≤11 follicles (n=43 mares) and high AFC as >11 follicles (n=34 mares). Data were analyzed by a mixed effect model, including AFC group, reproductive seasonality, and season (P≤0.05). UE was influenced (P=0.05) by reproductive seasonality. The conception rate was higher (P=0.016) in recipients with low (79.07%) than high AFC (61.76%) and higher (P=0.005) in cyclic (81.40%) than anestrus (58.82%) mares. In addition, we observed a tendency (P=0.06) for the interaction of AFC*reproductive seasonality, showing that high*anoestrus recipients had the lowest conception rate (37.50%b) compared to high*cyclic (83.33%a), low*anoestrus (77.78%a) and low*cyclic (80%a). The conception rate was higher in cyclic recipients with low AFC. Furthermore, UE was influenced by reproductive seasonality and mares in anestrus showed a higher degree of UE than cyclic mares.

Keywords: Antral follicle count; corpus luteum; embryo recipient; embryo transfer; horses.