Effects of combined Actinobacillus pleuropneumoniae challenge and change in environmental temperature on production, plasma insulin-like growth factor I (IGF-I), and cortisol parameters in growing pigs

There is limited information on the combined effects of stress factors on physiological and endocrinological parameters in growing pigs. This study measured the effects of pleuropneumonia and changes in environmental temperature singularly and in combination. Forty entire male pigs (liveweight 33 ± 5 kg) were allocated to 1 of 4 treatments: control (22 C room temperature), Actinobacillus pleuropneumoniae challenge (Day 1), temperature stress (15 C for 8 h on Days 0, 1, and 2, and 30 C for 24 h on Day 6), or combined A. pleuropneumoniae challenge and temperature stress. Control pigs had an average daily gain of 1.15 ± 0.12 kg/day and an average daily feed intake of 2.29 ± 0.06 kg/day over 8 days. Challenge with A. pleuropneumoniae caused a reduction (P < 0.001) in feed intake, weight gain, and plasma insulin-like growth factor I (IGF-I) concentration and an increase (P < 0.001) in plasma cortisol concentration. There was no significant effect of the temperature stress on circulating cortisol and IGF-I concentrations or liveweight gain. Thus, the treatment effects did not appear to be additive and the effects of the A. pleuropneumoniae challenge were more profound than changes in ambient air temperature.