Effects of repeated exposure to an estrus synchronization protocol on reproductive parameters in dairy goats

Repeated exposure to estrus synchronization (ES) protocol might have detrimental effects on reproductive function. Therefore, we examined the effects of repeated exposure to a gonadotropin-based ES protocol on hormonal profiles in 47 female Xinong Saanen dairy goats. Goats were randomly assigned to receive an ES protocol either three consecutive times with 14 d interval between each protocol (3 × ES group), or once (1 × ES group) starting concurrently with the third protocol of the 3 × ES group. The estradiol concentrations in 1 × ES group were significantly lesser than those of 3 × ES group at 0, 24, 36, 60 h after controlled internal drug release withdrawal. The progesterone, luteinizing hormone, and follicle-stimulating hormone concentrations did not differ between 1 × ES and 3 × ES groups. No differences (P > 0.05) were observed in the estrus interval, estrus duration, gestation length, birth weight of kids, and the incidences of estrus, pregnancy, single birth, twinning birth, triplet birth between 1 × ES and 3 × ES groups. Litter size was smaller in goats of the 3 × ES group than in 1 × ES goats, and there were more female offspring in 3 × ES group than 1 × ES group (P < 0.05). The differences in reproductive parameters warrant further investigation in a larger population of goats subjected repeated ES.