Technical and Economic Outcome using Various Timed Artificial Insemination Protocols in Dairy Cattle in the Tropics

Pregnancy rates and economic outcome in dairy animals reared under tropical conditions were determined following progesterone (controlled internal drug releasing device; CIDR)- or gonadotropin releasing hormone (GnRH)-based timed artificial insemination (TAI) protocol with GnRH or estradiol benzoate (EB) used as the ovulation synchronisation agents. Animals on the GnRH-based protocols were given GnRH (100 µg, i.m.) on day 0, prostaglandin F2? (PGF2? ; 25 mg, i.m.) on day 7 and were given either GnRH (GnRH-G; n=55) or EB (500 µg, GnRH-E; n=40) 48 hours after. Animals on the progesterone-based TAI protocol received a CIDR insert for 7 days, PGF2? at CIDR removal, and either GnRH (CIDR-G; n=73) or EB (CIDR-E; n=55) 48 hours later. All animals were artificially inseminated, 60-72 hours after the injection of PGF2? and pregnancy was determined at 25-35 d after insemination. The mean pregnancy per timed artificial insemination (P/AI) was 38.5 ± 3.3% and was not affected by treatments. P/AI was higher in progesterone-based (43.6%) compared to GnRH-based (26.8%) protocols in heifers but not in cows (P = 0.1). The cost of treatment was greater (P < 0.001) for progesterone ($20.2) than GnRH-based ($11.1) TAI protocols. The mean added value was higher for heifers on progesterone-based ($119.8) than those on GnRH-based ($73.6) protocols (TAI protocol X parity, P = 0.09). Progesterone and GnRH-based TAI protocols can be cost effective approaches for increasing pregnancy rates in heifers and cows, respectively under tropical conditions.