Seasonal Variation in Oestrus and the Secretion of Plasma Progesterone and Oestradiol in the Small East African Goats

Abstract

Oestrous cycles were monitored tor a period of 9 months (March - November) in normal cyclic  small  east  African  goats  to  ascertain  the  relationship of  their  ovarian activity and changes in local climatic conditions. Plasma progesterone and oestradiol-17 beta were assayed in the same goats for a period of 5 months (May - November) using radioimmunoassay (RIAS). Overt oestrus was detected with the aid of teaser bucks. Cyclicity was high and regular from March to the end of June in warm rainy season and decreased thereafter reaching minimum levels in mid-September in the dry cold season. Cyclicity was once again regular from Mid-October and November following the onset of short rains. The hormonal profiles paralleled the changes in the oestrous cycles. The results tentatively suggest that seasonality in ovarian activity do occur in the indigenous goats of East Africa in relation to changes in microclimatic conditions in this part of the tropics.