Seasonality of oestrus and ovulation in Corriedale ewes: repeatabilites and phenotypic correlations

Abstract

SUMMARYOestrus and ovulation data from 104 adult Corriedale ewes, recorded daily from February 1988 to May 1990 in Argentina, were analysed to estimate repeatabilities of and phenotypic correlations between onset and cessation of the breeding season, duration of the anoestrus and ovulation rate.The repeatability of dates of onset and cessation of the breeding season and duration of the anoestrus was 0·48±0·080, 0·49±0·075 and 0·50±0·081, respectively.The duration of the anoestrus was significantly correlated both with onset (r = 0·24; P < 0·05) and with cessation (r = –0·47; P < 0·01) of the previous and subsequent breeding seasons, respectively.There was no correlation between dates of onset and cessation of the breeding or non-breeding seasons.Repeatability estimates of ovulation rate were 0·27 ± 0·034, 0·34 ± 0·081 and 0·43 ± 0·094 using the normal, logit and probit scales, respectively. Phenotypic correlations between ovulation rate and the components of the breeding and non-breeding seasons were all non-significant.