The effect of active immunization against adrenocorticotropic hormone on cortisol, beta-endorphin, vocalization, and growth in pigs.
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 beta-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 beta-endorphin concentrations, but it did not modify ADG, ADFI, or restraint vocalization score in growing pigs.
Lee
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Faculty of Veterinary Science, The University of Sydney, Camden, NSW 2570, Australia. Caroline.Lee@csiro.au
Giles
L R
LR
Bryden
W L
WL
Downing
J A
JA
Collins
D C
DC
Wynn
P C
PC
D000324:Adrenocorticotropic Hormone / Q000276:immunology*; D000704:Analysis of Variance; D000818:Animals; D000906:Antibodies / Q000097:blood; D004435:Eating / Q000502:physiology; D006799:Housing, Animal; D006854:Hydrocortisone / Q000097:blood*; D007114:Immunization / Q000662:veterinary; D008297:Male; D011156:Population Density; D011897:Random Allocation; D013552:Swine / Q000097:blood / Q000254:growth & development / Q000276:immunology / Q000502:physiology*; D013997:Time Factors; D014828:Vocalization, Animal / Q000502:physiology*; D015430:Weight Gain / Q000502:physiology; D001615:beta-Endorphin / Q000097:blood*
D000906:Antibodies; D001615:beta-Endorphin; D000324:Adrenocorticotropic Hormone; D006854:Hydrocortisone