Characteristics of oestrus and conception rate in postpartum dairy cows induced ovulation by using 3000 iu of hcg in 5-day and 7-day cidr-based oestrus synchronisation protocols
M. P. Nayana, C. P. Abdul Azeez , K. Promod, Leeba Chacko and Lijo John
The aim of the study was to compare oestrus characteristics and evaluate the conception rate of postpartum dairy cows by inducing ovulation using 3000 IU hCG in 5-day and 7-day CIDRbased oestrus synchronisation protocols. Twenty-four apparently healthy, cyclic cows, which had completely involuted uterus as assessed by clinico-gynaecological examination and without any history of peripartum and postpartum complications were selected and randomly allotted into two treatment and one control group (n=8 each). On day 40 postpartum (Day 0), animals of Group I (5d CIDR group) were inserted with CIDR followed by administration of GnRH on the same day. The CIDR insert was removed on day 5 and and PGF2α administered. After 36 h of CIDR removal, 3000 IU of hCG was given followed by TAI at 50 - 56 h after CIDR removal. In Group II (7d CIDR group), similar protocol was followed as in group I, with the difference that CIDR was kept for 7 days. Animals in Group III (Control) were observed for occurrence of natural postpartum oestrus from day 40 till day 90 postpartum and inseminated at detected oestrus. The oestrus response, time taken for onset of oestrus, intensity of oestrus and duration of oestrus after CIDR removal were recorded. Pregnancy diagnosis was done on day 25 post AI through ultrasonography and on day 60 through transrectal palpation. The results demonstrated no significant difference in oestrus characteristics between group I and II but the 5-day CIDR-based protocol had higher overall conception rate and was superior to 7-day CIDR-based protocol when 3000 IU of hCG was used to induce ovulation in oestrus synchronisation protocols.
Key words: Oestrus synchronisation, post-partum dairy cows, CIDR, hCG