Changes in serum cortisol reveal functional differences in frustration-induced chain chewing in pigs

Area of Science:

• Animal behavior
• Neuroendocrinology
• Physiology

Background:

• Oral stereotypies are repetitive behaviors often linked to frustration or specific environmental conditions.
• The pituitary-adrenal axis is a key system involved in stress response and hormonal regulation.

Purpose of the Study:

• To investigate the pituitary-adrenal correlates of oral stereotypies in pigs under different feeding conditions.
• To compare the physiological responses to oral stereotypies induced by intermittent versus massed food presentation.

Main Methods:

• Pigs were exposed to either intermittent food distribution or a massed food situation, with a control group receiving intermittent food without a chain.
• Blood samples were collected on days 8 and 21 to measure serum cortisol levels.
• Behavioral observations focused on the development and rate of chain chewing.

Main Results:

• Both intermittent and massed food conditions induced high rates of chain chewing in pigs.
• Serum cortisol levels decreased in pigs under the intermittent food schedule by session 21.
• Serum cortisol levels increased in pigs under the massed food condition by session 21.

Conclusions:

• Oral stereotypies elicited by intermittent food presentation have different pituitary-adrenal correlates than those induced by massed food regimens.
• The physiological stress response, as indicated by serum cortisol, varies significantly depending on the feeding schedule associated with oral stereotypies.