or bleeding during insemination.Oestrus length, the time of ovulation, the number of piglets born, and the number of piglets born alive were analysed using the MIXED procedure, with the means com-pared by the Tukey-Kramer test. In the models used for theanalysis of oestrus length and time of ovulation, WOI andoestrus 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