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Effect of diferents levels of crude protein and metabolizable energy on the performance of Plymouth rock barred hens

This work was conducted to determine the effects of different levels of crude protein (CP) and energy (EM) in laying phase of Plymouth Rock Barred (PRB) hens. The birds were obtained at the Poultry Section of the Departament of Animal Science, at the Federal University of Santa Maria. At the 21st week (end of the growing phase), 384 females were selected and allocated in a laying house. These birds were submitted to four experimental diets, in each analised period, resulting in a factorial analysis (two levels of protein X two levels of energy) with 12 replications of eight birds. In the phase I (23th to 42th week) and the phase II (43th to 54th wek) levels of 15.5 and 17.0% of CP, 2700 and 2800kcal of ME/kg were used. In the second phase the protein levels decreased one percent unit, and the energy levels were the same. The productive performance was estimated through body weight, feed intake, egg production, egg weight, egg mass, feed conversion (kg/dz), egg specific gravify and the peak of egg to each breed. During the laying period it was used a factorial analysis (two levels of protein x two levels of energy) with 12 replications of eight birds, per breed. The analysis of variance were conducted for each period of 28 days and at the end of the experimental period. The Tuckey test was used when at least 5% of significance was obtained. Females PRB feddiet with 2800kcal of ME/kg of the diet showed significant increased in the laying rate (periods II, IV and V), in the egg mass (periods IV, V and VIII) and in the feed conversion (periods V and VI). For females RIR the higherst energy level gave a better feed conversion in the period I (P<.05). The variable body weigth, feed intake and egg specific gravity were not affected by any level and/or interaction used at the diffèrent phases. Further studies should be conducted to better evaluated this breeds.

Plymouth Rock Barred hens; laying period; levels of crude protein and metabolizable energy


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