Lying characteristics as determinants for space requirements in pigs

An experiment was carried out to study the lying postures, space occupation and percentage of space-sharing (as a consequence of huddling behaviour) in pigs. Information about these lying characteristics is essential for the calculation of lying space requirements, e.g. for pen design legislative purposes. The study included two replicates of eight groups of eight pigs each. Pigs were housed at thermoneutral conditions in 8 m(2) partly (40%) slatted pens from 25 to 100 kg live weight. Lights were on from 06:30 until 18:30 h. Feed and water were available ad libitum. Behaviour of the pigs was recorded for 48 h on video tape at approximately 30, 50, 80 and 100 kg live weight. General activity, lying posture (sternum, half recumbent, fully lateral recumbent) and space-sharing percentage were scored by 20 min scan sampling. The results confirmed that pigs of all weight categories lie down for a great part of the day: the average numbers of pigs that were lying were 83.8, 85, 86.3 and 87.5% at 30, 50, 80 and 100 kg live weight. Especially at night (18:30-06:30 h), the fully recumbent lying posture is predominant. The percentages of lying pigs that lied in the fully recumbent position in that period were 65.7, 66.4, 67.7 and 69.1 for 30, 50, 80 and 100 kg pigs, respectively. In our study, we observed that pigs spent little time in contact with conspecifics: space-sharing percentages were 20-40%. There was a significant period effect for the space-sharing data; pigs showed more 'social lying behaviour', i.e. tended to huddle more during the night in comparison to the day since the space-sharing percentages were higher during the night (P <0.01). Based on the observations carried out in this study, average space occupation figures were calculated for lying pigs: 0.30, 0.46, 0.64, 0.76 m(2) for 30, 50, 80 and 100 kg pigs. The present study confirms the suggestion of Petherick (1983) that, as a starting point for discussions about space requirements for pigs, the floor area occupied by lying pigs at thermoneutral conditions should on average be based on the estimated floor area for half recumbent pigs, i.e. area = 0.033 x bodyweight(0.66). (C) 2003 Elsevier Science B.V. All rights reserved