Superovulatory response of dairy cattle ( Bos taurus ) in a tropical environment

Dairy (Bos taurus) heifers and cows (n = 40) in a tropical environment were treated during mid-luteal phase using either SUPER-OVR or OVAGEN™ to induce superovulatory response after synchronization of the superovulatory estrus with a synthetic progestagen and cloprostenol (PG). Estrous cattle were inseminated twice using frozen-thawed semen, and embryos were recovered nonsurgically, on-farm, 7 d later. Between initiation of gonadotrophin treatment and recovery of embryos, 4 blood samples per animal were collected from 26 animals for determination of plasma progesterone (P4) concentration. Two (5%), 28 (70%) and 10 (22%) of the animals were observed in estrus 1.5, 2 and 2.5 to 3 d after PG, respectively. There was no difference (P = 0.7) in the number of palpable CL between animals treated with SUPER-OVR (7.6 ± 1.0; n = 18) and those treated with OVAGEN™ (7.9 ± 1.1; n = 22). There was also no significant difference (P > 0.05) between Jersey vs Ayrshire breeds or heifers vs cows in the ovarian response as estimated by the number of palpable CL. However, a higher proportion of Ayrshire cattle and donors treated with OVAGEN™ yielded a higher total number and viable/transferable embryos than Jersey and SUPER-OVR-treated cattle. There was a significant (P < 0.05) correlation between the number of CL and total number of embryos (r = 0.65); the number of transferable embryos was also significantly related to the total number of embryos per recovery (r = 0.85; P < 0.05). For 15 animals with normal P4 profiles, the mean (±SEM) plasma P4 concentration was 14.4 ± 0.8, 0.5 ± 0.2, 5.4 ± 1.1 and 39.4 ± 3.0 nmolL at initiation of gonadotrophin treatment, superovulatory estrus and Days 3 and 7, respectively. The mean (±SEM) interval between a PG injection given after embryo recovery and the induced estrus was 7.1 ± 0.7 d (range 3 to 14 d) and the length of the superovulatory cycle was 24.1 ± 3.2 d (range 12 to 35 d).