A note on the effect of gestation housing environment on approach test measures in gilts

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Systems’ welfare evaluation, including behavioural testing, is becoming increasingly popular in farm animal assurance schemes. The aims of this study were to investigate whether fairly short-term exposure to gestation housing systems, which varied in physical, environmental and human-input factors, influenced behavioural and physiological measures during a human approach test—often used to identify problems in human–animal interactions. Twenty-four Large White×Landrace gilts were initially subjected to identical human contact and daily husbandry. Forty-two days after service, the gilts were randomly assigned to either an indoor housing system (n=16) or an outdoor housing system (n=8), which differed physically and in the amount of human contact and daily husbandry. The indoor system used an electronic sow feeder (ESF), was more space-limited and thermally-controlled and had human contact centered on cleaning out. The outdoor system was more extensive, had much greater space accessible, was not thermally-controlled and had human contact that centered around feeding. The human approach test was carried out on all gilts 30–44 days after entry to the gestation system. At testing, each individual was fitted with heart rate monitor and then moved into a test arena. After 2min an unfamiliar human entered the pen and stood motionless for 3min against one wall and then approached the gilt and touched her snout. Throughout the experimental period, behaviour and sound within the test arena were recorded continuously. During the 2min familiarisation period, outdoor gilts had lower heart rates (108.2bpm versus 123.7bpm, P<0.05) and tended to perform fewer short vocalisations (0.5calls per min versus 3.4calls per min, P<0.1). Outdoor-housed gilts also carried out less locomotor behaviour (2.2 sections crossed versus 4.0 sections crossed, P<0.05) and tended to perform fewer short (1.4calls per min versus 5.0calls per min, P<0.1) and long vocalisations (0.2calls per min versus 1.8calls per min, P<0.1) over the 3min test period. Outdoor gilts tended to be slower to approach within 0.5m of the human (69.9s versus 19.3s, P<0.1) but they then took less extra time to make physical contact (3.3s versus 52.7s, P<0.1). Mean heart rate was significantly lower in outdoor sows over the whole 3min period (99.5bpm versus 115.5bpm, P<0.05). The results demonstrate that short-term exposure to different housing systems did influence behavioural and physiological measures during a standard human approach test and thus, systems differences should be taken into account before making judgements about the human–animal relationship on any commercial farm, based on results of behavioural tests of this type.