Ewe body condition determines oestrus response to hormonal oestrus synchronization in smallholders village flocks

Abstract

 The objective of this study was to investigate the effects of ewe associated factors on hormonal oestrus synchronization in village sheep flocks in Sidama zone, Southern Ethiopia. Initially, for synchronization fifty-five Sidama ewes were selected and checked for pregnancy status using pregnancy diagnosis device (Preg-Tone). The ewes were injected with a single shot of PGF2α (Lutalyse®) hormone at the rate of 2.5 ml per ewe. Thirty-eight of the 55 ewes treated with hormone showed oestrous signs. The ewes were then joined with active selected four breeding rams for four consecutive days. Oestrous response and conception rates were analyzed using multinomial logistic regression model. The overall oestrous response rate and conception rate were 69.1% and 89.2%, respectively. The average time to onset of oestrus was 54.1 hrs, ranging from 19.1 to 97.5 hrs. Neither ewe body weight (P = 0.902), age (P = 0.127) nor parity (P = 0.968-0.084) had significant effect on the oestrus response rate of ewes to hormonal oestrus synchronization. The only significant factor determining oestrus response was ewe body condition. Ewes with body condition score of 2.5 and below were significantly more likely not to respond to hormonal treatment (odds ratio = 2.15E-09, P = 0.000) compared to ewes with body condition score of 3.0. However, none of the factors studied (body condition, body weight, age and parity of the ewe) affected the time of onset of estrus after hormone administration and conception rate. It could be concluded that body condition, regardless of the other ewe associated factors (i.e. body weight, age and parity), dictates oestrus response of ewes to hormonal treatment in synchronization of oestrous cycles in village ewe flocks. It is thus imperative to pay attention to nutrition of ewes for successful synchronized breeding in villages where supplementary feeding is rarely practiced.