Preparing gilts for group housing by increasing their social skills

Abstract

Former experiments have shown that social experience during nursing in either a group housing system with straw or a very spacious farrowing/nursing pen with straw, increases social skills of growing pigs considerably. Based on experiences in Taiwan, it was postulated that such skills could also be acquired in the period between being taken from flatdecks at 10 weeks of age and the age of 5 months. In an ‘arena’, copied from the one used for introducing new pigs (gilts) in a group housing system, agonistic behaviour and number and severity of lesions of the integument of 384 experimental GY × DUROC hybrid gilts were studied and compared with data of an equal number of control gilts in three different treatments (repeated once). The experimental animals were born in individual farrowing crates with slatted floors. They were weaned at 30 days and kept in flatdeck cages with two other litters, until 10 weeks. At that time they were kept in groups of eight on fully slatted floors and treated with regrouping and repenning several times until the final testing at an age of 5 months. In sequential experiments, this treatment was given twice, three times or four times and effects on social (agonistic) behaviour were studied. The control animals were born in a group farrowing house with straw, where they stayed 30 days (some days after weaning). As for the experimental pigs, two litters were grouped in flatdeck cages. At 10 weeks of age they were moved to pens with fully slatted floors, where they remained in groups of eight undisturbed until final testing at 5 months. At an age of five months, eight unfamiliar experimental animals were grouped in a so-called arena for 24 h. So were 8 control pigs in the same week. Time-lapse video observations during these 24 h (2 frames/s) revealed that the pigs were fighting for social dominance during this period. Experimental pigs that had been regrouped four times only showed 57% of bilateral agonistic actions and 82% of total fighting time, in comparison with control pigs. Three times regrouping still showed a statistically significant lower amount of fighting, but twice regrouping did not. After 24 h in the arena, the number of lesions of the integument was significantly smaller in groups that had experienced regrouping 3 or 4 times. These results proved that social experience by regrouping and repenning prepared gilts for agonistic encounters, by improving their social skills.