Dietary Lysine and Ascites Incidence

Losses due to ascites are of considerable concern in the production of meat-type chickens. There is widespread belief that any factor that promotes pulmonary hypertension may increase ascites incidence. The increased blood flow that occurs at low rearing temperatures increases ascites incidence. The physiological changes that lead to the development of ascites are described by Julian [l]. The underlying metabolism causing these physiological changes is not well understood. Wideman et al. [2] have studied arginine supplementation of the diet. Arginine is a substrate for nitric oxide and a powerful endogenous pulmonary vasodilator. Supplemental arginine reduced cumulative pulmonary hypertension syndrome mortality and lowered right:total ventricle heart weight ratios. Chickens are dependent upon dietary sources since they do not synthesize arginine at a rate sufficient to obtain maximum growth. Taylor et al. [3] and Dietert et al. [4] have shown that dietary arginine levels sufficient for maximum growth are lower than arginine levels sufficient for maximum production of nitric oxide. The interrelationship between arginine and lysine has been well documented. Dietary lysine is directly correlated with kidney arginase activity [5]. Further, the low environmental temperatures that increase ascites incidence also cause increased plasma lysine concentration [6]. Lysine is a limiting amino