Immunization against cholecystokinin decreases appetite in lambs.

The effects of immunization against cholecystokinin (CCK) on feed intake, weight gain, and carcass characteristics were studied in sheep. Nine wether lambs at 10 wk of age were immunized with a conjugate of sulphated CCK octapeptide and human serum globulin or against human globulin alone. All CCK-immunized lambs produced antibodies, and the average titer 5 wk after the primary immunization was calculated to be sufficient to bind normal circulating levels of CCK. Mean daily feed intakes and BW were similar in the CCK-immunized and the control-immunized groups at the start of treatment, but after immunization, feed intake, appetite, and BW gain were decreased in the CCK-immunized animals. There was no effect on carcass composition or organ growth relative to body growth. It is concluded that the immunization procedure used in this study may have potentiated the actions of CCK rather than neutralizing its action as an appetite regulator.