Manipulation of Fertility in Crossbred Dairy Cattle Using Controlled Internal Drug Release Device Combined With Prostaglandin and Equine Chorionic Gonadotrophin

Simplifying and improving our understanding of the protocols for inducing or synchronizing estrus is important for improving management of dairy cattle. This study evaluated the estrus response and conception rate of crossbred (Holstein Friesian X Zebu) dairy cows (n=75) and heifers (n=47) assigned to a 10-day controlled internal drug release (CIDR) device – prostaglandin F2-alpha (PGF2α) – equine chorionic gonadotrophin (eCG) based estrus synchronization protocol. Animals were assigned to three groups (a) anestrus (n=62), (b) repeat-breeders (n=11) and (c) silent estrus (n=46), according to their reproductive history, per rectal palpation, and progesterone concentrations determined by On-Farm enzyme-linked immunosorbent assays (ELISA) in milk (lactating cows) or serum (dry cows and heifers). For each animal, a CIDR device (containing 1.38g progesterone) was inserted into the vagina and allowed to remain in-situ for 10 days. On Day 8 after device insertion, a dose of 500µg of PGF2α was administered intramuscularly (IM). On Day 10 (device removal), 500 IU of eCG was given IM. Animals were inseminated or mated 48 and 72 hrs post device removal. Pregnancy was assessed 20-24 days post insemination by measurement of progesterone in milk/serum and pregnancy was confirmed by per rectal palpation and/or ultrasonography 44-90 days post insemination. Overall estrus response and conception rates were 97.5% and 78.3%, respectively, with no significant differences in parity, pre-treatment reproductive status and farming system (smallholder vs organized commercial farms). Conception rate after induced/synchronized estrus was 82.9% and 72.1% in cows and heifers, respectively, with an overall calving rate of 94.4%. In conclusion, the present study has shown high estrus response and conception rate in crossbred dairy cattle using this CIDR - PGF2α - eCG based estrus synchronization protocol. Application of this protocol is highly recommended to enhance fertility of dairy cattle in the study area, and this could readily be applied to other regions.