Effects of different levels of rapeseed meal and diet formulation based on total vs. digestible amino acids on performance of broiler chicks

An experiment was conducted to investigate the effects of different levels of rapeseed meal and diet formulation based on total and digestible amino acid (AA) using 192 day old Ross 308 male broiler chicks. Experiment was carried out using a complete block design with 4*2 factorial arrangements. The factors included different levels of rapeseed meal (0, 10, 20 and 30%) and two method of AA formulation (based on total or digestible AA requirement). Four replicates of 6 chicks were fed dietary treatments from 11 to 49 d of age during two period of grower (11-28 d of age) and finisher (28-49 d of age). Feed intake and weight gain of each experimental unit was measured at 28 and 49 d of age and then feed conversion ratio was calculated. At 28 and 49 d of age, blood sample were taken from wing vein of 2 birds per replicate and then T3 and T4 concentration of the sample were measured. Results show that different levels of rapeseed meal had no significant effect on feed intake. Diets containing 20 or 30 % rapeseed meal had highest and lowest weight gain, respectively, during the grower and finisher period. Method of formulation of AA requirements had significant effect on weight gain so that chicks fed diets formulated on the basis of digestible AA had significantly higher weight gain. Feed conversion ratios were affected by both different levels of rapeseed meal and method of diet formulation. Feed conversion ratios were increased by 30 % rapeseed meal, whereas 20% rapeseed meal significantly lowered it. Formulation of diets on the basis of digestible AA also decreased feed conversion ratios. Results obtained in our study suggest the inclusion of 20% rapeseed meal and diet formulation based on digestible AA when rapeseed meal are used in the broilers diets.