Evaluation of three classification methods of antral follicle count and fertility to the timed artificial insemination in cattle

Abstract

The controversial data about antral follicle count (AFC) may be partially explained by the different criteria used to determine what is high, intermediate and low AFC. This study evaluated different classification methods for AFC groups, relating them to the conception rate, dominant follicle size and body condition score (BCS) in cows submitted to timed artificial insemination (TAI). Nelore cows (Bos indicus; n = 935), received a reproductive program consisting of TAI and natural breeding. Conception rate, BCS and dominant follicle size during TAI were evaluated by three AFC methodologies: i) mean and standard deviation: low (≤ 15 follicles); intermediate (≥ 16 to ≤ 44 follicles) or high (≥ 45 follicles); ii) quartiles: low (≤ 15 follicles); intermediate (≥ 16 to ≤ 39 follicles), or high (≥ 40 follicles); and iii) AFC score: I (low; ≤ 15 follicles); II (intermediate; ≥ 16 to ≤ 30 follicles); III (high; ≥ 31 to ≤ 44 follicles) or IV (very high; ≥ 45 follicles).Data were analyzed by a GLIMMIX and Tukey test or binary logistic regression model (P ≤ 0.05). The conception rate to TAI was influenced (P < 0.05) by AFC in the three methods classification, being the highest conception rate observed in the low AFC group regardless of method utilized: Mean (low 61.73% a , intermediate 54.02% ab and high 49.48% b ), Quartiles (low 61.73% a , intermediate 53.59% ab and 51.46% b ) and Score (I 61.73% a , II 54.80% ab , III 53.23% ab and IV 49.48% b ). There were variations (P < 0.05) in the conception rate within the 2.50 to 2.75 BCS range for all AFC classification methods, with the low AFC females presenting the best results, regardless of the method used. Also, females with low AFC showed larger (P < 0.05) diameters of dominant follicles at the TAI regardless of method. The different methodologies used (Mean, Quartile and Score) to AFC classification showed a consistency between the main findings, and we believe that this standardization will facilitate the interpretation of data involving AFC.

Reproductive performance of fixed-time artificial insemination in heifers supplemented with a homeopathic complex

“…The AFC is also an important indicator because it is related to fertility and has been the focus of several studies (Burns et al, 2005;Ireland et al, 2011;Morotti et al, 2018). AFC is a highly variable characteristic among animals, but it is highly repeatable in the same individual (Ireland et al, 2007), which allows the classification of females into low, medium, or high AFC groups (Morotti et al, 2022(Morotti et al, , 2018Silva-Santos et al, 2014). In addition, AFC is strongly correlated with anti-mullerian hormone (AMH) concentrations in both Bos indicus and Bos taurus (Guerreiro et al, 2014), and can be a reliable method for predicting AFC (Ireland et al, 2011;Rico et al, 2011).…”