Estimation of sensible heat loss in capsaicin- desensitized chicken after exposure to disruption of thermal homeostasis

الملخص EN

Background : Thermal conditioning In newly hatched chicken is of great importance.

Induction of thermotolerance to cold, heat and disrupted thermal balance Is one of the most important managemental tools used to improve survival in chicken.

It Is well known that chicken Is in sensitive to capsaicin (main Ingredient of hot chilli peppers) due to insensitlvity of Transient membrane potential of vanilloid subtype-1 (TRPV1) receptors to capsaicin.

These receptors are responsible for perception of pain burning sensation and thermoregulation In mammals.

Owing to the capsaicin's availability as an rodent repellent function in poultry radon and its preference by many birds, we investigated the mechanism of thermoregulation of capsaicin in chicken The purpose: To interpret the phenomenon of thermotolerance in capsaicin (CAP) desensitized chicken and to study its effect on sensible heat loss mechanisms in newly hatched chicks.

Methods: In this study, chicken were treated intravenously (IV) in wing vein once with CAP (10 mg/kg, body weight) at 1st, 2nd & 3rd days of age.

Then after one week from CAP- pretreated chicken were exposed to cold (8°C), heat (38°C) or injected with lipopolysacccharide (LPS; outer memebrane of Gram negative bacteria).

LPS at a low dose (1 mg/kg, body weight, IV) induce fever or at a high dose (10 mg/kg, IV) to induce hypothermia.

Surface (skin of back) and colonic temperatures were measured to calculate heat loss Index (HLI) as an Indicator to the sensible heat loss.

Main results: The HLI was 0.95 in control non-treated chicken at ambient temperature (Ta 25°C).

In CAP-desensltized chicken HLI was increased to a maximum of 0.97 at Ta 38°C and up to 0.99 at climax of fever induced by LPS.

The controversial finding was observed in chicken exposed to cold; HLI In CAP-desensitized chicken was not increased but reduced to 0.94, however no such effect of capsaicin at nadir of hypothermia induced by high dose of LPS.

Conclusion: CAP-sensitlve receptor (Transient membrane potential of vanilloid subtype-l;TRPVl> independent pathway may exert a thermoregulatory role during heat and cold exposure, and In LPS-induced fever In part through affecting sensible heat loss in chicken.