Effects of active immunization against cholecystokinin 8 on performance, contents of serum hormones, and expressions of CCK gene and CCK receptor gene in pigs

This study was conducted to investigate the effects of active immunization against cholecystokinin 8 (CCK₈) on the content of serum CCK, expression of CCK, and CCK receptor gene in pigs. The subjects for this experiment were 15 pigs divided into three groups (5 pigs per group). The treated groups were immunized with CCK₈ conjugated to human serum albumin (HSA). The control group was immunized with same dosage of HSA. The average daily gain of pig fed with 250 μg CCK was significantly increased (P < 0.05), compared with the control group (0 μg CCK). The content of CCK₈, insulin, and leptin in serum was significantly (P < 0.05) decreased and the titer of CCK₈ antibody was significantly (P < 0.05) increased in treated groups compared to the control group. The levels of CCK gene and CCK receptor gene expression in jejunum, pituitary, and pancreas of the treated groups were significantly (P < 0.05) lower than that of the control group. It is concluded that optimal active immunization against CCK₈ could increase the content of CCK antibody and suppress CCK gene and CCK receptor gene expressions and in result improve feed intake and growth performance of pigs. Keying Zhang and Zhongbiao Yuan have contributed equally to this work.