In the models used for the analysis of oestrus length and time of ovulation, WOI and oestrus length were respectively used as covariates. Thefixed effect of treatments, the random effect of the boar,the week of the study, and the age of the semen, in additionto the mean lifetime number of born piglets, as a covari-ate, were included in the models used for the analysis ofthe number of piglets born and the number of piglets bornalive