Effect of Dietary Crude Protein and Metabolizable Energy Levels on the Performance of Laying Hens.

Abstract

The present experiment was conducted to determine the extent the performance of young laying hen was affected by dietary crude protein (CP) and metabolizable energy (ME) levels, preceeding a series of experiment to determine the requirement of each essential amino acid.Seven hundred twenty pullets of a commercial strain were housed two birds per cage in an open convention-ventilated laying house and fed twelve diets ad libitum from 150 to 255 days of age. Three replicate (240 birds per replicate) were involved. Mean daily temperature ranged from 15° to 25°C during the experimental period. Experiment had a 4×3 factorial arrangement of treatment with four levels of CP and three levels of ME.The diets were formulated for methionine, lysine and tryptophan to reach 85, 95, 105 or 115% of the NRC recommendations and contained graded levels of dietary ME (2, 700, 2850 and 3, 000 kcal/kg).Significant diet differences for feed intake, egg production, egg weight, egg mass, body weight gain and feed conversion ratio were noted. Increasing the dietary energy resulted in reduced feed intake and a general tendency to increase energy intake. But feed consumption was not affected by dietary CP levels. Increasing the protein level of the diet resulted in increased protein intake but had no effect on energy intake. Throughout the whole experimental periods, egg production increased with increasing CP levels. The egg production rate was not affected by ME level till 192 days of age, but it tended to decrease with increasing ME level after that age. Egg weight increased with age on all diets. It increased with increasing CP level until 234 days of age, but was not affected by ME level throughout all experimental period. Since egg weight increased with age on all diets and egg production rate increased with increasing CP levels, egg mass also increased with age and by CP levels in the similar way as egg weight and production rate. As protein and energy levels increased, efficiency of feed utilization increased.The present study showed that the CP level which maximized hen performance was 14.5% or more across all ME levels and on the protein requirements of laying hens indicated that for maximum production of about 90%, hens required about 18 grams of protein per day. Present experiment also have suggested that in a moderate environmental temperature (from 15° to 25°C) ME levels of 2, 700-2, 850 kcal per kg diet might give economical results. The daily energy requirement of the hens for maximum production of about 90% ranged from approximately 310 to 330 kcal ME per day.