ffects of different levels of digestible arginine and protein in starter diets containing ideal amino acids ratio on eperformance, carcass traits and serum parameters in broiler chickens

introduction: nutrition and health during the first days of life has critical effect on broiler chickens performance. it is well known that diet formulation based on digestible nutrients is superior to formulation based on total nutrients. the suitable supply of essential amino acids in broilers’ diets requires proper knowledge on their metabolic effects in the body. the excessive or unbalanced intake of essential and non-essential amino acids can be harmful to broilers’ metabolism, due to amino acid antagonisms. arginine is an essential amino acid for broilers since the urea cycle is not functional in birds. arginine involves in the synthesis of ornithine, a precursor of polyamines that have a key role in cell division, dna synthesis, nitric oxide (no) synthesis, and cell cycle regulation. also, arginine increases the release of insulin, growth hormone, and igf-a and luteinizing hormone (lh) in the blood stream. on the other hand, in corn- soybean meal based diets arginine is the fifth limiting amino acid after methionine, lysine, threonine, and valine. thus, this study was carried out to investigate the effects of different digestible arginine (da) and digestible protein (dp) levels of starter diets (1-10 d) based on ideal amino acids ratio on performance, carcass traits and serum parameters in broiler chickens. materials and methods: four handed day-old male broiler chickes (ross 308) were distributed in 10 treatments of 4 replicates (floor pens) each. the experiment was designed as a 2×5 factorial arrangement in a completely randomized design. experimental diets were formulated with five levels of digestible arginine (1.05, 1.18, 1.31, 1.44 and 1.57%) and 2 levels of digestible protein (18 and 20%). chicken were fed with experimental diets during 1 to 10 days of age, and then received similar diets formulated according to ross 308 (2009) recommendations. all birds had free access to feed and water during the whole rearing period. temperature was initially set at 32 °c on d 1 and decreased linearly by 0.5 °c per day up to 42d and kept constant thempreture. during the study, the birds received a lighting regimen of 23 l: 1 d from d 1 to 42. weight gain, feed intake and feed conversion ratio were measured weekly. blood samples were collected from wing veins of birds at 10 d of age. after 15 minutes, the blood samples were centrifuged at 3000xg for 15 minutes and serum samples were separated into tubes. then, serums were stored at -20ºc until analyses were carried out. at 10 and 42 d of age, one bird from each pen with body weight close to the mean of each pen were selected for carcass analyses. after feed withdrawal, the selected birds were transported to the university pilot for processing. the chickens were slaughtered by cervical dislocation to determine the carcass characteristics. data were analyzed by analysis of variance using glm procedures (sas, 2001). means were compared using duncan's new multiple ranges test (duncan, 1955). the level of significance was reported at (p < 0.05). resuls and disscusiion: the results showed that feed intake, daily weight gain and feed to gain ratio (fcr), as well as their interactions were significantly affected by (digestible argenine, da) and (digestible protein, dp) levels in starter diet. the best feed conversion ratio during starter period was related to 20 % da and 1.31 % da. dp levels in starter diet had a significant effect on relative weights of liver and abdominal fat (af) on day 10 and relative weights of gizzard and ileum and also relative lengths of duodenum and ileum on day 42. da levels significantly affected liver and af relative weights on day 10. da and dp interactions had significant effects on relative weight of liver and relative lengths of duodenum, jejunum and ileum on day 10 of age. effects of dp levels on serum total protein, albumin and phosphorus concentrations were significant. da levels had significant effects on serum concentrations of uric acid and calcium. conclusion: the results of current study showed that dietary recommendations of digestible arginine and digestible protein by ross 308 company support male chicken’s growth performance.