Three years of research on manipulable materials in Italian heavy pig production: a synopsis

A total of 168 animals was used in 4 independent trials, comparing the effects on the behaviour of growing-finishing undocked Italian heavy pigs (30-170 kg BW) of the following manipulable materials: 1) suspended metal chain; 2) wood logs inside a rack; 3) edible block inside a rack, 4) wood attached to a metal chain; 5) wood log held by a metal frame; 6) edible block held by the frame. In each experiment two of the above-mentioned enrichments were compared. Animals were kept in small groups (4 pigs/pen) on slatted floor. Pigs were videotaped over the diurnal hours (12h) approximately every three weeks. Individual behaviours were assessed by scan-sampling. Observations from the 4 trials (1400 individual ethograms) were subjected to one-way ANOVA, using the enrichment device as the main effect and the trial as the random effect. All animals were in good health throughout the trials. None of the proposed six enrichment devices significantly (P>0.05) affected the main individual behavioral patterns (proportion of time committed to: standing inactive, sitting inactive, lateral laying, sternal laying, rooting/exploring). The most observed behavior was laying, ranging from 61 to 73%. No aggressions or tail biting outbreaks were recorded. Conversely, depending on the trial, some unknown experiment-related factors resulted in significant differences for all the observed behaviors. Given the similarities in terms of general behavior obtained on pigs under good rearing conditions, it is suggested that factors other than enrichment devices may play an important role on the welfare level of heavy pigs.