Stimulation of food intake and growth of swine by cholecystokinin immunization.

Experimental superalimentation at 30% above ad libitum intake increased growth 40% and confirmed that voluntary food intake is a growth-limiting factor in swine. A sequence of contingent hypotheses was proposed for swine: cholecystokinin (CCK) is a regulator of food intake; food intake is enhanced by reduction of serum CCK; serum CCK is reduced by anti-CCK antibodies: anti-CCK antibodies are raised by active immunization. The objectives of this study were to determine if antibodies were raised in immunized swine and if the anti-CCK titers were sufficient to increase food intake and growth. Twelve young growing swine were immunized against cholecystokinin (CCK-8) to test the hypothesis that anticholecystokinin antibodies in serum would suppress cholecystokinin inhibition of appetite (food intake). An equal number of control animals (hSG) were immunized against the antigenic carrier protein by the same protocol. Specific binding of [125I]CCK-8, the C-terminal octapeptide, by sera diluted 1:181 increased to a peak value on day 43. Food intake and body weight gain were similar for the two groups during the first phase of the study. However, food intake was 8.2% greater and body weight gain was 10.6% greater for the CCK-8 than for the hSG group during the second phase (d 43 to d 77). Total food intake over the 77-day study was 5.4% greater for the CCK-8 group (P = .08): body weight gain was 8.3% greater (P = .006). Regression analyses confirmed that gain over the 34-day second phase increased .076 kg (P = .045; R2 = 0.34) for each percentage unit increase of serum binding.(ABSTRACT TRUNCATED AT 250 WORDS)