The effect of passive immunization against ghrelin on feed and water intake in turkeys

Five-week-old turkeys were used to evaluate the effect of passive immunization against ghrelin on feed and water intake and animal behavior. In experiment 1, females were reared using normal feeding and lighting management recommended by the industry. At 5 wk of age (d 0 of experiment 1), birds (n = 40) were individually caged (0.65 × 0.4 × 0.4 m) with free access to feed and water. Feed and water intake were measured 3 times a day (0800, 1200, and 1700 h) by recording the weight of feed or water offered minus any unconsumed feed or water remaining. After 3 d of adaptation to the cages (d 3), birds were stratified by BW and feed consumption and randomly assigned to a 2 × 5 factorial arrangement of treatment. Starting on d 3, turkeys were given intravenous (iv) injections (0.5, 1.0, 2.0, 4.0, or 8.0 mL) of pooled undiluted plasma obtained from pigs that were previously actively immunized against ghrelin or iv injections (0.5, 1.0, 2.0, 4.0, or 8.0 mL) of pooled undiluted plasma, obtained from nonimmunized pigs (control). In experiment 2, the 2 highest doses (i.e., 4.0 and 8.0 mL; n = 4/treatment) were repeated in a 2 × 2 factorial arrangement as described in experiment 1. A laptop computer with a built-in color camera and appropriate software was used to record birds for 9 consecutive hours, starting 4 h before treatments were applied. Video clips were saved and a human observer watched and annotated bird behavior associated with feeding, drinking, and standing. Passively immunized birds increased feed consumption (P = 0.04) compared with control animals. Water intake was not affected by treatments. There was a tendency for immunized birds to increase the number of pecks per hour and the amount of time devoted for feeding. Our data suggest that in turkeys, the effect of immunization against ghrelin on feed intake is the opposite of that observed in mammalian species.