Ingestive Behavior of Meat and Egg-Type Chickens: Equal Sensitivity to Naloxone

Abstract

The efficacy of the opioid antagonist naloxone in attenuating ingestive behavior in stocks of chickens genetically selected for either meat (Rock-Cornish, RC) or egg production (Single-Comb White Leghorn, SCWL) was investigated. Because the stocks differ markedly in growth rate, two experiments were conducted to compare RC and SCWL cockerels at similar body weights and at the same age. Birds were injected intramuscularly with either isotonic saline or naloxone HCl at a dose of 5 mg/kg body weight. Food and water were offered ad libitum 15 min postinjection. In RC and SCWL stocks of similar body weight, naloxone significantly attenuated cumulative food and water intake through 210 min following the return of food and water. When administered to RC and SCWL stocks of the same age, naloxone significantly attenuated cumulative food intake for 300 min and cumulative water intake at 60 and 120 min. The relatively long-term depressions in cumulative food and water intake were attributable to significant decreases in incremental consumption within early time periods. There was no significant difference in the efficacy of naloxone in attenuating ingestive behavior when the stocks were compared at either similar body weights or at the same age. The results demonstrate that genetic selection for meat or egg production has not significantly altered opioid mechanisms regulating food and water intake in the domestic fowl.

Research Note: Naloxone Inhibits Drinking in the Chick Induced by Angiotensin II

“…The reduced water intake noted in those treatments where naloxone was administered is in agreement with previous work in the chicken (McCormack and Denbow, 1987) although All was not administered in those studies. Studies using rats as the experimental animal have shown attenuation of drinking induced by AH by naloxone at a 5 mg/kg BW dosage (Summy-Long et al, 1981a).…”

“…Injection of AH alone increased water intake of chicks to 12 h when compared with the saline-injected controls, but the effects were no longer evident at 24 h. Naltrexone injection did not have any effect on the Allinduced increase in water intake. The reduced feed intake to 4 h noted with the opioid antagonists has been documented previously in domestic fowl (McCormack and Denbow, 1987). Cumulative food intake was reduced in the AH, naltrexone, and naloxone groups at 1 h when compared with the control group (Table 2).…”

“…In the first trial four treatments with 10 chicks per treatment were used: a control (saline), AH (1 mg/kg BW), naloxone (5 mg/kg BW), and naltrexone (10 mg/kg BW were determined in preliminary trials and from the work of McCormack and Denbow (1987). In the first trial four treatments with 10 chicks per treatment were used: a control (saline), AH (1 mg/kg BW), naloxone (5 mg/kg BW), and naltrexone (10 mg/kg BW were determined in preliminary trials and from the work of McCormack and Denbow (1987).…”

“…Opioids have been shown to increase both feed and water intake (McKay et al, 1981). The opioid antagonist naloxone attenuates these effects in the chick (McCormack and Denbow, 1987).…”