Evaluation of muscle protein turnover of broiler with different genetic groups created in cyclic heat stress through analysis of environmental stable isotopes

Abstract

The aims of the project are to test the exposure of birds at high temperatures reduces the protein turnover in muscle and this effect is much more intense when the bird are genetically improved, and that there is an interaction between the protein level, group muscle, genetic groups and different temperature treatments. Two experiments (I and II) will be conducted from 21 to 45 days old birds, and up to 21 days of age the birds receive the same diet based on plants of the C3 photosynthetic cycle and will be established at thermoneutral temperature. At 21 days the lot will be weighed and will be assembled experimental units with chickens of the same weight and will consume a diet based on plants of the C4 photosynthetic pathway. Assimilation during photosynthesis, plants whit photosynthetic cycle C3 fix atmospheric CO2 by Clavin-Benson cycle and have values between -22 and -34 13C 0. C4 plants fix CO2 via the Hatch-Slack cycle and have values between -9 to -16 0. Negative sign indicates that the plants have lower concentrations of 13C than the international standard. Therefore, the C3 and C4 plants have different isotopic signatures (13C/12C), due to fractionation that occurs during photosynthetic carbon fixation. This difference in the natural isotope ratio allows us to do diets with distinct isotopic patterns, which can be used as natural tracers, without the need to synthesize compounds specifically marked with the use of radioactive isotopes that can cause environmental or health problems. In experiment I will use 720 broilers, male, commercial line Cobb 500 ® and in the experiment II will use 720 broilers, males, slow growth line. Both experiments will be distributed in a completely randomized in a factorial 3 x 3, with the factors: temperature (cyclic stress of heat ad libitum, 22 ° C ad libitum, and 22 ° C constrained) and protein levels (18.0; 20 and 22.0% CP), a total of nine treatments with four replicates of 20 birds each, totaling 36 experimental units. In the cyclic stress of heat the animals are reared in a scheme oscillating temperature for 16 hours at room temperature will be thermoneutral and 8 hours in an environment that will have a peak heat, start with 22 ° C gradually increases the temperature to 32ºC and returned to 22°C , trying to simulate the field conditions of poultry production.Birds on treatment 22 C restricted, will receive the same daily amount of feed consumed by birds in the treatment of cyclic heat stress. This scheme will allow isolate the temperature effect of cyclic heat stress effect of low feed intake caused by heat stress.The control diet of the experiments will be formulated with nutrient levels suggested by COBB (2009b): 18.0% CP, 0.90% calcium, 0.45% phosphorus, 0.19% sodium, 0.82% methionine + cystine total, 1.05% lysine and 3176 kcal / kg metabolizable energy (ME). Diets with high protein content (22 and 24%) will have the nutrient levels and ME similar to the control diet.Will be evaluate the performance and carcass characteristics, the protein turnover of the muscles Pectoralis major, Sartorius and liver. In both group muscles the fibers count will be conducted, establish of the frequencies (%) and obtaining the diameter.The data will be subjected to analysis of variance through the General Linear Model (GLM) of SAS ® and in case of significant differences are the averages compared by Tukey test at 5% probability. (AU)