Seasonality of estrus and ovulation in Creole goats of Argentina

Abstract

Adult non-pregnant and non-lactating native Creole does ( n=9) were used to characterize the seasonal variations in estrous and ovarian activity during a period of 18 month beginning in January. The goats were maintained in an open barn under constant nutritional levels, natural photoperiod and daily exposure to males. Vasectomized bucks were used twice daily to detect estrus, and ovarian activity was monitored by assessing serum progesterone concentrations from blood samples collected twice weekly. Live weight was recorded at monthly intervals. During the first year, the proportion of ovulating animals increased gradually from February to April (6/9–9/9), remained elevated (July, 9/9) and then declined gradually between August and September (7/9–4/9). No ovulations were recorded between October and February (following year). During the second year, the proportion of ovulating does increased gradually from March to April and all the females remained cycling throughout the end of the experimental period. A similar distribution was observed for estrus although with a slightly shorter period of anestrus between November and January. Maximal and minimal periods of sexual activity were associated with winter and summer solstices, respectively. During the periods of sexual activity (breeding season), there was a higher proportion of estrous cycles (associated estrus and ovulation) around the winter solstice whereas dissociated cycles (estrous behavior only or silent ovulation) were more frequent at the beginning and at the end of the breeding season. Similarly, the proportion of cycles of abnormal duration (either short or long) was higher at the beginning and at the end of the breeding season. The native Creole does in Argentina, fed constantly throughout the year, exhibit a seasonal pattern of reproduction.