Abstract

An experiment was done using 176 one day-old, broiler chicks of commercial line available in Syrian market. The birds were randomly distributed into four groups according to nutrient treatment received in the diet. These groups were divided into four groups; the first group (control) fed the control diet conforms to (NRC, 1994) requirements, the second group received a diet in which calory to protein ratio c/p =130 in first age and c/p =150 in second age and contains the same nutrients as control birds of first group, the third group fed the same as the control one, but with the addition of 20% methionine + cystine, the fourth group received a diet the same as the second one with the addition of 20% methionine + cystine. Increasing of protein or methionine or both had no clear effects on live body weight. Treatment did not affect feed intake. Feed intake decreased by adding methionine, or adding both methionine and protein together in the diet. There was slight amelioration in feed conversion ratio when increasing methionine, while increasing both protein and methionine together gave the best result. Treatments had no clear effect on lymphoid organs weight, or total white blood cell count. Newcastle disease antibody titer increased by methionine (P<0.05), this is indicate that the additional methionine is important to improve immune response to Newcastle disease. Mortality was not significantly different.