Influence of Physical and Olfactory Environment on Swine Aggression

156 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1981.One thousand and six young crossbred pigs were used in a series of applied ethological studies and one physiological study. The objective of these studies were to identify sources of variation in swine aggressive behavior and to better understand mechanisms which modulate fighting. The social dynamics within groups of four pigs were quantified. Duration of attack was not significantly different than zero by two to four hours after regrouping three replicates. One replicate required 26 hours to reach minimal aggression. Use of the feeder and some resting areas, duration of attack and body weight were not highly correlated. The data indicate that individual pigs show differential use of resources; however, a pig which dominates one resource does not necessarily dominate another. The second study provided pigs areas to "hide" their head and shoulders. Provision of these "hides" resulted in 40 per cent less fighting and fewer wounds. Hide pens or regrouping did not affect pig gain or feed efficiency during a 21-day trial. The third study suggested pigs give off odors which alter fighting among experimentally naive pigs. Urine from fighting pigs, when coated on the skin of other pigs, reduced fighting of the other pigs. Pigs not fighting, moved to another pen, had urine properties which increased fighting among test pigs. This differential effect, observed using aggressive and unaggressive urine from barrows and gilts, was not observed from similar samples obtained from boars. The suggested reproductive pheromone, 5(alpha)-androst-16-en-3-one, reduced the duration of fighting by 85 per cent while in another experiment, testosterone did not influence pig aggression. Testosterone did reduce the increase in fighting induced by corticosterone application. These results suggest an androgen reduced fighting and a glucocorticoid increased fighting. In the final study, preliminary neurophysiological data indicated that 5(alpha)-androst-16-en-3-one increased electical activity of the olfactory bulb in the freely-moving conscious young pig. The results suggest strong olfactory modulation of swine aggression.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD