Induction of oestrus in post-partum anoestrus cows with crestar, GnRH and hCG

Abstract

Anoestrus cows (36), 50-55 days postpartum, were divided in to 4 groups of 9 each, viz, control (group 1 ), treatments 1 (group 2), 2 (group3) and 3 (group 4). Crestar was implanted subcutaneously in group2 cows are kept it in situ for 7 days. Before 12 hr of implant removal, PGF2n(25 mg dinoprost trometha~ninew) as adrninistcred i/m and after 48 hr of PGFZn treatment, 20 µg, buserelin, was injected i/m. Group 3 was similar to group 2 except cows in this group received 1 more GnRH along with crester, whereas in group 3,cows were administered 2000 IU hCG (chorulon) i/m along with crestar and 48 hr post PGF2a treatment in place of GnRH. All the treated animals were inseminated twice, at 16 and 24 hr after second GnRH/hCG treatment. The control cows were inseminated 12 and 24 hr after the onset of oestrus. Oestrus was induced in all (100%) the treated cows of groups 2,3 and4 at an interval of 61.56±0.60,60.11±0.51 and 60.78±0.66 days postpaartum, respectively, compared to only 55.56% control cows exhibiting natural oestrus in group 1 by 138.80±18.21 days. Conception to first service at induced oestrus was 11 . I I% in groups 2 and 3 and 22.22% in group 4. In control group I , 20.00% cows conceived. Ovarian cyclicity was restored in 88.89,55.56 and 77.78% treated cows in groups 2, 3 and 4, respectively, compared to 44.44% cows in control group. The overall conception rates in groups 1 (20.00%), 2, 3 (22.22%) and 4 (44.44%) were not different statistically.