EBVma is expressed as deviation from the population mean (population mean is a number between 0 and 100). From a study carried out by Knol et al. (2002), it was concluded that the sow's EBVma, rather than her piglets’ genetic merit for vitality, is related to the litter average time interval between piglet expulsion and first colostrum intake. A short interval is essential for survival of piglets. Piglets born from a group of sows with a high EBVma had a shorter mean interval from birth until first colostrum intake than piglets born from sows with lower EBVma (±40 min versus ±100 min). The difference in EBVma between both groups of sows was 9.18% (minimum: −4.92%, maximum: +4.26; overall mean = 0.79). Knol et al. (2002) also showed that the difference in interval from birth until first colostrum intake between sows with different EBVma is not related to differences in udder and teat morphology. Possibly, differences in maternal behaviour during parturition between sows with different EBVma may explain the difference in length of this interval (Fig. 1).