version ISSN 1668-3498
VEIGA, P et al. Effect of different esters of estradiol used to synchronize ovulation on pregnancy rate to FTAI in Angus heifers. InVet [online]. 2011, vol.13, n.2, pp. 39-45. ISSN 1668-3498.
Three experiments were conducted (EI, n: 209; EII, n: 208; y EIII, n: 188) using Angus heifers in order to compare the use of estradiol cypionate (EC) at device removal or estradiol benzoate (EB) 24 h after in a FTAI protocol. On day 0 heifers received a progesterone intravaginal device plus EB. On day 8, the intravaginal device was removed and heifers received a luteolytic dose of PGF. At device removal heifers were randomized to receive either EC at 0 h or EB at 24 h. On day 10, 50-53 h after device removal, fixed timed artificial insemination was performed using frozen/ thawed semen of proven fertility (3 bulls for EI and 2 for EII and EIII) and two inseminators. Pregnancy rates were not different between treatments (EI: 67.8%; EII: 59.2%; EIII: 58.4%) or inseminators (p>0.05); however a bull effect was observed in experiments I (B: 47.8%; F: 75.0%; M: 72.0%; p<0.05) and II (M: 68.8%; ME: 48.5%; p0.05). Interactions were not significant. In conclusion, according to our finding, estradiol cypionate could be used instead of estradiol benzoate to synchronize ovulation without affecting the pregnancy rate at fixed timed artificial insemination.
Keywords : Progesterone; Estradiol cipionate; Heifers; FTAI; Pregnancy.