The Thai Journal of Veterinary Medicine


Sixty seven from 2,500 of fifty percenť Freisian-native crossbred heifers at "The Promotion of Calves Rearing Project", Chantuk, Nakornrajasima north east province of Thailand were treated with new PRIDs, (Progesterone Releasing Intravaginal Devices) attached with 10 mg oestradiol benzoate capsule. PRIDS were inserted for 12 days, then removed. The animals were divided into 2 groups, treated with PRIDs and PRIDS plus PMSG 500 i.u. intramuscular injection on the day of removal. Percentage of synchronized estrus heifers of those two groups were 54.84 and 88.98 respectively. Removed PRIDS were inserted to another 38 heifers, 19.05% became heat when treated with PRIDs alone and 29.41% became heat combined with PMSG. A11 animal received a fixed time insemination at 56 h after PRIDS removal. The conception rates at the induced estrus were 17.86% 37.15%, 21.05% and 6.25% in heifers treated with new PRIDs, new PRIDs plus PMSG, reused PRIDs and reused PRIDS plus PMSG respectively. New PRIDS plus PMSG showed a significant synchronized oestrus but no differences in conception rate.



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