Litter competition during nursings and its effect on sow response on Day 2 postpartum

The aim of the present study was to assess neonatal sibling competition during nursing on Day 2 postpartum (pp) as well as its effect on the sow's responses. A total of 41 healthy loose-housed sows and their piglets were directly observed and video recorded for 6 h on Day 2 pp. Piglet behaviours (presence at the udder, fighting, and screaming) were scored in 15 s intervals, commencing 5 intervals (i.e. 75 s) prior to milk ejection and for 9 intervals (i.e. 135 s) after milk ejection. The proportion of piglets which missed the milk ejection, postural changes by the sow, and whether the nursing was with milk ejection were also noted. The mean number of piglets per litter exhibiting fights (FIGHTS), and exhibiting fights with screams (FIGHT-SCRES) was calculated for before (pre-massage) and after milk ejection (post-massage). While the number of piglets with FIGHT-SCRES was higher during pre-massage than during post-massage (0.28 vs. 0.18 piglets, P < 0.01); the number of piglets with FIGHTS did not differ between pre- and post-massage (1.28 vs. 1.19 piglets). A higher number of piglets with FIGHTS (P < 0.0001) and FIGHT-SCRES (P < 0.0001) were associated with a higher proportion of piglets missing a milk ejection. There were no significant effects of the number of piglets with FIGHTS or FIGHT-SCRES detected on the probability of non-nutritive nursings or sow posture changes during pre-massage. However, a higher number of piglets with FIGHT-SCRES increased the probability of a sow terminating post-massage with posture changes (P < 0.05). In conclusion, low piglet competition on Day 2 pp, and the threshold level of 1–2 piglets involved in neonatal litter competition appears to be too low to prevent milk ejection, although sows changed posture after milk ejection due to piglet competition with vocalizations.