SUPEROVULATORY RESPONSE OF DAIRY-CATTLE (BOS-TAURUS) IN A TROPICAL ENVIRONMENT

Dairy (Bes taurus) heifers and cows (n=40) in a tropical environment w ere treated during mid-luteal phase using either SUPER-OVR or OVAGEN(T M) to induce superovulatory response after synchronization of the supe rovulatory estrus with a synthetic progestagen and cloprostenol (PG). Estrous cattle were inseminated twice using frozen-thawed semen, and e mbryos were recovered nonsurgically, on-farm, 7 d later. Between initi ation of gonadotrophin treatment and recovery of embryos, 4 blood samp les per animal were collected from 26 animals for determination of pla sma progesterone (P4) concentration. Two (5%), 28 (70%) and 10 (22%) o f 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 palpabl e CL between animals treated with SUPER-OVR (7.6+/-1.0; n=18) and thos e treated with OVAGEN(TM) (7.9+/-1.1; n=22) There was also no signific ant difference (P>0.05) between Jersey vs Ayrshire breeds or heifers v s 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(TM) yielded a higher total number and viable/transferable embryos than Jersey and SUPER-OVR-treated cattle. There was a signifi cant (P<0.05) correlation between the number of CL and total number of embryos (r=0.65); the number of transferable embryos was also signifi cantly 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) plasm a P4 concentration was 14.4+/-0.8, 0.5+/-0.2, 5.4+/-1.1 and 39.4+/-3.0 nmol/L at initiation of gonadotrophin treatment, superovulatory estru s 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 cycl e was 24.1+/-3.2 d (range 12 to 35 d) (C) 1997 by Elsevier Science Inc .