THE RELATIONSHIP BETWEEN FOOD-CONSUMPTION AND PERSISTENCE OF POST-FEEDING FORAGING BEHAVIOR IN SOWS

There remains some uncertainty regarding the roles of internal and ext ernal factors in the organization of feeding behaviour. In the pig (Su s scrofa) there are important scientific and welfare-related reasons f or determining the extent to which feeding behaviour is largely pre-pr ogrammed or, alternatively, responsive to the environment. To examine the sensitivity of feeding behaviour in the pig to external stimuli th e effect of food reward frequency and size on the post-feeding behavio ur of sows was tested in three experiments in a sand-filled test arena . In Experiment 1a, five treatment and five control sows were observed for 45 min day(-1), 5 days a week for 3 weeks. In the second week a s ingle food pellet preceded by a buzzer was presented three times durin g a test period for treatment sows. The sows initially responded by se arching after the discovery of the pellet, but this response declined with time (mean no. of bouts: 11.6, 15.8, 16.4, 10.2, and 6.4 for Days 1-5, respectively; P < 0.01). All ten sows searched for 16 food pelle ts buried in the sand in Experiment 1b, and they responded to the decl ining encounter rate by decreasing searching behaviour. In Experiment 2 nine sows were observed for 35 min day(-1) for 18 days and were give n zero, three pellets or 1 kg of pellets in a Latin square design whic h was replicated twice, The searching response increased with reward s ize (mean proportion of observed time: 0.005, 0.017 and 0.038 for rewa rd sizes 1-3, respectively; P < 0.001), but had declined by the second reward (mean proportion of observed time: 0.027 and 0.013 for Replica tes 1 and 2, respectively; P < 0.01). It was concluded that although t he ingestion of food in the pig may initially result in short-term pos itive feedback effects on feeding motivation, this response is strongl y modifiable by experience. As there was little evidence that sows ent er a 'pre-programmed' loop of feeding behaviour, processes other than those normally associated with foraging must be used to explain the oc currence of persistent oral behaviour shown in intensively farmed pigs .