Cholecystokinin octapeptide immunization: effect on growth of barrows and gilts

A study was conducted to validate the previously reported growth response to cholecystokinin octapeptide (CCK-8) immunization in barrows and was extended to include gilts. Group-penned barrows and gilts were used to represent conditions in the swine industry. Thirty-two animals, 19 barrows and 13 gilts, were randomly assigned by sex to four pens and two treatments. The control groups were immunized with human serum globulin (HSG). The treated groups (CCK) were immunized with the C-terminal octapeptide of cholecystokinin conjugated to human serum globulin. Specific binding of CCK-8 was confirmed at 29 d after the primary inoculation. Antisera titers were highly variable throughout. The mean titer reached a peak on d 57 and then declined. Body weight gains during the last 49 d, the period during which titers were expressed, were compared by ANOVA. The treatment effect on gain was significant (P = .018); the sex effect approached significance (P = .071); the treatment X sex interaction effect was not significant (P = .82). Least squares mean gain of the CCK group was 8.4% greater than of the HSG group, 41.4 vs 38.2 kg, respectively. A significant linear regression coefficient for gain vs antisera titer was obtained for barrows (P = .03; r2 = .44) but not for gilts. Several carcass variables showed trends similar to that of BW gain, but the treatment effects were less robust (P < .05 to .10). These results generally confirm the findings of the previous study; CCK-8 immunization stimulated growth of barrows by 7.5% in the present and by 10.8% in the previous study. The CCK-8 immunization seemed to stimulate growth of gilts by 9.3% in the present study.