Role of Essential Amino Acids in the Early Formation of Avian Liver Xanthine Dehydrogenase Activity

¹ From the Departments of Agricultural Biochemistry and Poultry Husbandry, Rutgers, The State University, New Brunswick, New Jersey

Avian liver xanthine dehydrogenase (LXD) has been shown to be sensitive to dietary proteins and amino acids particularly when measured during the first 3 weeks of life. Feeding an adequate diet for the first 7 days of life produces a condition wherein LXD is very resistant to single essential amino acid deficiencies. When an amino acid-deficient regimen is fed directly, without prefeeding an adequate diet, a rapid and marked decrease is seen which is inversely proportional to the amount of available limiting amino acid. This mechanism has also been demonstrated by LXD depletion with low dietary protein and repletion with diets high in protein but limiting in a specific amino acid. In the case of l-threonine deficiency, a dietary level of threonine above that required to saturate a growth response produced a continuous rise in LXD specific activity similar to induction.