THE EFFECT OF AGONISTIC INTERACTIONS ON THE HEART-RATE OF GROUP-HOUSED SOWS

Inter-sow aggression can be a major welfare problem in group-housing s ystems and can also affect productivity, This experiment investigated the effect of different types of agonistic interaction using heart rat e as an indicator of physiological response. The heart rates of nine L arge White x Landrace sows housed in a large group with an electronic sow feeder system, were monitored during agonistic interactions. Inter actions were categorised into: (1) interactions involving physical con tact, (2) non-physical interactions involving threat only. Both were r ecorded as win or loss, giving a total of four encounter types, The da ta were analysed to give the peak heart rate value during the encounte r and also the increase from the pre-encounter mean to the peak value. Although there were some statistical difficulties presented by small sample size, sows involved in physical encounters had a greater increa se in heart rate and a higher peak value (+ 59.1 beats per min (bpm), 137.0 bpm) than sows involved in threat encounters (+ 31.6 bpm, 107.3 bpm). Sows which lost a physical encounter tended to have the highest heart rates (+ 85.7 bpm, 157.7 bpm), The results demonstrate that all sows involved in agonistic encounters show an acute and transient resp onse indicated by a rise in heart rate; however, the rise is greatest for sows which lose a physical encounter.