Comparison of Estradiol Cypionate and Estradiol Benzoate Effects on Ovaric Activity, Estrus and Ovulation on Anestrus Bos indicus Cows

The objective was to compare the effect of Estradiol Cypionate (EC) vs. Estradiol Benzoate (EB) on follicular population, ovulation rate, percentage of animals in estrus and Estrus-Ovulation knterval (E-OI) in non-cycling Bos indicus cows. Three groups of eleven cows each and similar Body Condition Score (BCS) were implanted with a CIDR cattle device at day 0 and given I mg of EB and after nine days CIDR was removed. EC group (BCS = 5.1) received 0.5 mg of EC + 25 mg of PGF(2 alpha); EB group (BCS = 5.0) received 25 mg of PGF(2 alpha) and 24 h after CIDR withdrawal were given 0.5 mg de EB; Control group (CC = 5.2) received 25 mg of PGF(2 alpha) + 1 mL of saline solution. From CIDR removal day, ovary activity was monitored by ultrasonography (US) at 0, 24, 48 and 60 h and later every 12 h until ovulation. Heat detection was conducted three times a day and Corpus Luteum presence (CL) was confirmed after 13 days of estrus with US. No statistical differences (p>0.05) were found for any of the variables. After CIDR removal the small and medium follicle populations were the same and one large follicle per cow developed. The ovulation rate was of 73% for EC, 100% for BB and 100% for control group. The percentage of cows in. heat was of 73% for EC, 82% for EB and 54% for control group. The E-OI was between 30 and 32 h. It was concluded that using EC or EB had no effect over the variables studied.