Dietary L-Carnitine Supplement Counteracts Pulmonary Hypertensive Response in Broiler Chickens Fed Reduced-Protein Diets and Subjected to Cool Condition and Hypobaric Hypoxia

Abstract

The present study was carried out to evaluate the effects of supplementing reduced-protein diets with L-carnitine on growth performance and occurrence of pulmonary arterial hypertension (PAH) syndrome in broiler chickens reared at high altitude. A total of 156 day-old male broilers (Ross 308) were assigned to three dietary treatments and reared up to 42 days of age. A normal-protein diet (NPD) was formulated according to the National Research Council (1994) and served as control. A reduced-protein diet (RPD) was also prepared to contain 3% less protein than that of the NPD. An additional RPD diet was prepared by supplementing L-carnitine (LC) at 100 mg/kg to the RPD. Results showed significant improvements in feed:gain and carcass yield in birds fed on RPD when supplemented with LC. The proportions of liver, heart, and abdominal fat pad relative to body weight and the right ventricular weight ratio (RV:TV) were significantly higher in birds fed on the RDP than those of the control fed the NPD. Electrocardiogram (ECG) measurements recorded from lead II supported the development of PAH in birds fed RPD as evidenced by deep S waves. Supplementing LC to the RPD significantly reduced the liver weight, abdominal fat deposition, and RV:TV, which reflected in reduced S waves. Feeding broilers with the RPD significantly reduced serum concentrations of nitric oxide (NO) and uric acid (UA). However, supplementation of the RPD with LC significantly increased the serum concentrations of NO. In conclusion, feeding reduced-protein diets to broilers reared at hypobaric hypoxia increases their susceptibility to pulmonary hypertension. Dietary LC supplementation of reduced-protein diets had beneficial effects in preventing PAH mortality mainly through enhancing blood NO concentration.