Anti-Müllerian Hormone (AMH), antral follicle count (AFC), external morphometrics and fertility in Tabapuã cows

•Vulvar width was an indicator of higherantral follicle counts.•Anti-Müllerian Hormone and antral follicle counts arecorrelated in Tabapuã breed.•Vulvar width and AFC werw associated positively with thoracic and pelvic depth. The intense selection of characteristics related to animal performance may affect the reproductive efficiency of beef cows negatively. Selection for fertility along with production traits is, therefore, readily justifiable. The objective of the present study was to evaluate possible relationships among AFC, serum AMH concentrations and external morphometrics with reproductive efficiency in Tabapuã (a Brazilian Bos indicus beef breed) females. Antral follicle counts and external morphometrics were measured in nulliparous (n = 162), primiparous (n = 80) and multiparous (n = 351) cows, from four farms. Age at first parturition (AFP), parturition interval (PI), maternal ability (MA), precocity, rusticity and survival (PRS) and overall reproductive efficiency (RE) were evaluated according to the Brazilian Association of Zebu Breeders (ABCZ) data bank indexes. A single blood sample per animal was collected at random stages of the reproductive cycle from a subset of animals (nulliparous = 84, primiparous and multiparous = 136) to determine serum AMH concentrations. The AFC classes were defined as lesser (50). Correlations between all variables and the effects of parity and AFC on reproductive traits, AMH and external genitalia size were analyzed by the PROCORR and by the PROCGENMOD procedures of SAS® (SAS, Cary, NC, USA), respectively. Antral follicle count did not differ (P = 0.71) among nulliparous (38.6 ± 23.96) primiparous (47.54 ± 26.16) and multiparous (41.08 ± 25) cows and was negatively correlated with pregnancy interval (PI), such that, as PI decreased (r = −0.28; P