Effect of different digestible lysine levels on performance, immune response and blood parameters of broilers in starter period

This study was carried out with the objective of determination of the optimal digestible lysine level in starter period (1 to18 days old) based on the performance، blood parameters and immune response in Arian male and female broilers by feeding diets formulating on digestible amino acids basis. A total of 240 male and female chicks were used with initial weight of 44 ± 1 g. The birds were distributed in a completely randomized design، using six treatments and four replecations، with 5 chicks each. Chickens were kept in thermostatically controlled batteries. The experimental treatments consisted of a lysine-deficient basal diet that was supplement with L-lysine HCl in order to contain six digestible lysine levels (0. 68، 0. 8، 0. 92، 1. 04، 1. 16 and 1. 28 %). Diets were isoenergetic، isonitrogenous and equal in electrolyte balance (Na + K + CL–). All diets met an ideal amino acid ratio recommended Illinois university for all other amino acids. Feed and water supplied for ad libitum consumption and a 24-h constant light schedule was mainted. In this phase، there was a significant effect of digestible lysine levels on body weight، feed intake، feed conversion ratio، blood parameters and immunity. Increase of digestible lysine level to 1. 28 % resulted in: maximum body weight (490. 60 and 426. 02 gr.)، plasma lysine level (160 and 140 ηmol/ml) for male and female respectively، and immune response، minimum feed conversion ratio (1. 20 and 1. 41 for male and female respectively). As digestible lysine level increased in diet، total count of white blood cell significantly increased in both sexes. Changes in number of all kind of WBC (heterophyle، Lymphocyte and monocyte) followed of that profile (were like changes in WBC count or were similar). There was the best of plasma albumin level and carcass N deposition in 1. 16 % and 1. 04 % of digestible lysine diet level for male and female respectively. As a result in order to minimize of disease incidence and performance improvement، 1. 28% digestible lysine as optimum level in diet can be suggested. Therefore requirement for optimum immunity is higher than performance.