Because the poor growth performance of intensively housed pigs is associated with increased circulating glucocorticoid concentrations, we investigated the effects of glucocorticoid suppression by inducing a humoral immune response to ACTH on physiological and production variables in growing pigs. Grower pigs (28.6 ± 0.9 kg) were immunized with amino acids 1 through 24 of ACTH conjugated to ovalbumin and suspended in diethylaminoethyl (DEAE) dextran-adjuvant or adjuvant alone (control) on d 1, 28, and 56. The ACTH-specific antibody titers generated suppressed increases in cortisol concentrations on d 63 in response to an acute stressor (P = 0.002; control = 71 ± 8.2 ng/mL; ACTH-immune = 43 ± 4.9 ng/mL) without altering basal concentrations. Plasma ÃŸ-endorphin concentrations were also increased (P < 0.001) on d 63 (control = 18 ± 2.1 ng/mL; ACTH-immune = 63 ± 7.3 ng/mL), presumably because of a release from negative feedback on the expression of proopiomelanocortin in pituitary corticotropes. Immunization against ACTH did not alter ADG (P = 0.120; control = 1,077 ± 25; ACTH-immune = 1,143 ± 25 g) or ADFI (P = 0.64; control = 2,719 ± 42; ACTH-immune = 2,749 ± 42 g) and did not modify behavior (P = 0.681) assessed by measuring vocalization in response to acute restraint. In summary, suppression of stress-induced cortisol responses through ACTH immunization increased ÃŸ-endorphin concentrations, but it did not modify ADG, ADFI, or restraint vocalization score in growing pigs.
|Number of pages||8|
|Journal||Journal of Animal Science|
|Publication status||Published - 2005|
Lee, C., Giles, L. R., Bryden, W. L., Downing, J. A., Collins, D. C., & Wynn, P. (2005). The effect of active immunization against adrenocorticotropic hormone on cortisol, ÃŸ-endorphin, vocalization, and growth in pigs. Journal of Animal Science, 83(10), 2372-2379.