Effect of cyclicity and Equine Chorionic Gonadotropin (eCG) in fixed-time artificial insemination programs in Bos indicus cattle/Efecto de la ciclicidad y la eCG en programas de inseminación artificial a tiempo fijo en ganado Bos indicus/Efeito da eCG e a ciclicidade em programas de inseminação artificial em tempo fixo em gado Bos indicus

The fixed-time artificial insemination (FTAI) programs in Bos indicus heifers have low pregnancy rates. The aim of this study was to evaluate the effect of cyclicity and equine chorionic gonadotropin (eCG) FTAI programs in Bos indicus cattle. A total of 100 heifers were assigned to four treatments using a completely randomized design with a 2 × 2 factorial arrangement, where one of the factors was ovarian status (cyclic or acyclic) and the other was eCG use (with and without eCG). Follicular growth, ovulation, and pregnancy rates were evaluated using analysis of variance or X^sup 2^ test. No effect of cyclicity on follicular diameter was observed while eCG showed a significant effect. Cyclicity status and eCG use had no significant effect on ovulation or pregnancy rates. The eCG application at the time of intravaginal device withdrawal increased the size of the ovulatory follicle on insemination day. However, the ovarian state and the use of eCG did not affect ovulation and pregnancy rates of the heifers.