Productive performance of Mexican Creole chickens from hatching to 12 weeks of age fed diets with different concentrations of metabolizable energy and crude protein

The study aimed to evaluate the productive performance, carcass yield, size of digestive organs and nutrient utilization in Mexican Creole chickens, using four diets with different concentrations of metabolizable energy (ME, kcal/kg) and crude protein (CP, %). Two hundred thirty-six chickens, coming from eight incubation batches, were randomly distributed to four experimental diets with the following ME/CP ratios: 3000/20, 2850/19, 2700/18 and 2550/17. Each diet was evaluated with 59 birds from hatching to 12 weeks of age. The variables feed intake (FI), body weight gain (BWG), feed conversion (FC), mortality, carcass yield, size of digestive organs, retention of nutrients, retention efficiency of gross energy (GE) and CP, and excretion of N were recorded. Data were analyzed as a randomized block design with repeated measures using the GLIMMIX procedure of SAS, with covariance AR (1) and adjustment of degrees of freedom (Kendward-Roger), the adjusted means were compared with the LSD method at a significance level of 5%. The productive performance variables BWG, mortality, carcass yield, fat and GE retention and excretion of N were not different (p>0.05) due to the diet effect. In the 3000/20 diet, the chickens had lower values of FI, FC, crop weight, gizzard weight, retention and retention efficiency of CP (p