The opioidergic system plays a critical role in feed intake, among other physiological functions. This study investigated the potential effects of the opioidergic system, leucine and its interaction with the central regulation of feed intake in broilers. 108 one-day-old Ross 308 broiler chickens in six groups, each with three replicates (n=6) have been used. A guiding cannula was implanted into the right lateral cerebral ventricle. Seven days later, leucine (2 µg), morphine (250 pmol), naloxone (5 µg), morphine + leucine combination (250 pmol +2 µg), naloxone + leucine combination (5 µg + 2 µg), and normal saline were injected intracerebro-ventricularly (ICV) (injection volume = 10 μl, n = 6, each with three duplicates). The cumulative feed intake was measured at 30, 60, 90, 120, 180, and 240minutes post injection. Naloxone increased feed intake, whereas both leucine and morphine significantly reduced it (p<0.05). ICV injection of morphine increased the inhibitory effect of leucine on feed intake (p<0.05). Additionally, within the first 60 min post injection, the combination of leucine and naloxone increased feed intake (p>0.05), whereas naloxone mitigated the inhibitory effect of leucine during the same period (p>0.05). The feed intake remained significantly decreased up to 240 minutes following the ICV injection of the combination of leucine and naloxone (p<0.05). Leucine appears to decrease feed intake through mechanisms involving glutamate and neuropeptide Y.
