Changes in serum cortisol reveal functional differences in frustration-induced chain chewing in pigs.
The pituitary-adrenal correlates of oral stereotypes in pigs were studied in two frustration situations of intermittent food distribution in which small amounts of food were given every 4 min (n = 4), and a massed food situation in which the same total amount of food was given in one meal at the beginning of the session (n = 5). Control animals (n = 6) were exposed to intermittent food but without a chain. Both intermittent-food and massed-food pigs developed chain chewing at similarly high rates. Blood samples were taken on days 8 and 21 of the experiment. Serum cortisol decreased between the beginning and the end of session 21 in intermittent-food pigs, but increased in pigs subjected to the massed-food condition. These findings suggest that oral stereotypies elicited by an intermittent schedule of food presentation are not equivalent to those elicited by the massed-food regimen.
D000818:Animals; D005502:Food; D005639:Frustration; D006854:Hydrocortisone / Q000097:blood*; D008297:Male; D008409:Mastication; D012055:Reinforcement Schedule; D013239:Stereotyped Behavior / Q000502:physiology*; D013552:Swine / Q000502:physiology*
D006854:Hydrocortisone