Application of hormonal subdoses at the Bai Hui acupoint for estrus synchronization in sheep

Abstract

Here, the efficiency of applying subdoses of equine chorionic gonadotropin (eCG) and prostaglandin F2α (PGF2α) at the Bai Hui (BH) acupoint for estrus synchronization in sheep was evaluated. Thirty Santa Inês ewes received intravaginal sponges containing 60 mg medroxyprogesterone acetate for 7 days. The animals were divided into five treatments (T) (n=6): T1 (control), 132.5 μg PGF2α (100% of dose) and 300 IU eCG (100% of dose), both intramuscularly (IM); T2, 39.75 μg PGF2α (30% of dose) at the BH acupoint and 300 IU eCG (100% of dose) IM; T3, 132.5 μg PGF2α (100% of dose) IM and 90 IU eCG (30% of dose) at the BH acupoint; T4, 39.75 μg PGF2α (30% of dose) and 90 IU eCG (30% of dose), both at the BH acupoint; and T5, 39.75 μg PGF2α (30% of dose) and 90 IU eCG (30% of dose) both at a false acupoint (IM, at the same location as in T1). After 12 h of sponge removal and hormone application, the ewes were subjected to monitoring for estrus and mating and ultrasound assessments of follicular growth and ovulation time every 12 h. The data were evaluated for normality and subjected to analysis of variance, considering a 5% probability. There were no differences in the percentage of animals in estrus (93.3±9.1%), interval from sponge removal to estrus onset (48.1±6.0 h), interval from sponge removal to estrus end (69.6±5.4 h), duration of estrus (24.0±4.7 h), interval from sponge removal to ovulation (73.7±5.9 h), interval from estrus onset to ovulation (26.5±2.3 h), size of the largest follicle (6.7±0.4 mm), follicular growth rate (0.8±0.1 mm•day-1), number of ovulations (1.3±0.1), and plasma progesterone levels 7 days after ovulation (9.6±2.0 ng•mL-1). The cost of the synchronization protocol per animal was US$ 4.37, 4.12, 2.96, 2.71, and 2.71 for T1, T2, T3, T4, and T5, respectively, with 37.99% cost reduction using PGF2α and eCG at 30% of the conventional doses. Therefore, the application of reduced PGF2α (39.75 μg) and eCG (90 IU) doses at the BH or false acupoint effectively synchronized estrus and reduced protocol cost in sheep, indicating that the conventional doses are overestimated.