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

Abstract

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.

Effects of peripheral administration of ghrelin antagonist [D-Lys<sup>3</sup>]-GHRP-6 on growth performance and blood biochemical indices in broiler chickens

“…Furthermore, the results reported in this study, as shown in Table 2, are in agreement with those of Lin et al (2011) who reported less food intake in mice with ablation of ghrelin receptor. Nevertheless, the results observed in this study with respect to decreased feed intake in chickens, given in Table 2, contradict those of Vizcarra et al (2012), who studied active immunization of ghrelin in turkeys. Such different research results may be attributed to the differences in the mechanisms of appetite/feed intake regulation (that is, the mechanism of ghrelin immunization differs with GHS-R antagonism) in poultry species (Kaiya et al, 2007 and also different birds strains (Saneyasu et al, 2011).…”

Capromorelin, a ghrelin receptor agonist, increases feed intake and body weight gain in broiler chickens (Gallus gallus domesticus)

“…Similar results were observed when a ghrelin agonist, GHRP-6, was centrally administered in 3-day-old chicks ( Khan et al., 2006 ). In addition, previous studies in our laboratory showed an increase in FI and peck rate in turkeys passively immunized against ghrelin ( Vizcarra et al., 2012 ) as opposed to decreased FI in actively immunized mammals ( Vizcarra et al., 2007 ).…”

“…A manual scoring option that integrated pause, rewind and forward choices was used to score start-stop behaviors (sitting and standing) and point events (number of pecks). The videos were watched and analyzed by a human observer as previously described in our laboratory ( Vizcarra et al., 2012 ).…”

“…Ghrelin is a short neuropeptide, secreted primarily by the oxyntic cells in the stomach of several species ( Kojima et al., 1999 ). The effect of ghrelin on appetite, glucose homeostasis and energy balance has been reported in mammalian ( Vizcarra et al., 2007 ; Kitazawa et al., 2013 ), avian ( Shousha et al., 2005 ; Kaiya et al., 2007 ; Vizcarra et al., 2012 ) and amphibians ( Shimizu et al., 2014 ) species. In mammals, ghrelin is known to stimulate feed consumption and to promote adipogenesis ( Wren et al., 2001 ; Shimizu et al., 2014 ).…”

“…Therefore, in mammalian species, ghrelin is known as an orexigenic hormone ( Tschöp et al., 2000 ; Kaiya et al., 2012 ; Tsuchiya et al., 2017 ). However, studies in avian species indicate that appetite is suppressed when ghrelin concentrations in bloodstream are elevated ( Saito et al., 2002 ; Vizcarra et al., 2012 ). Also, intracerebroventricular ( ICV ) administration of ghrelin inhibits feed intake in birds ( Furuse et al., 2001 ; Saito et al., 2002 ; Saito et al., 2005 ) whereas, peripheral administration of ghrelin at different doses have shown controversial results ( Shousha et al., 2005 ; Kaiya et al., 2007 ; Taofeek et al., 2020 ).…”