Response of chicken broilers to early graded levels dietary protein and energy
270 day old Arbor Acre broilers of a mixed sex were used to investigate the effects of different dietary protein and energy levels on performance, nutrient absorption capability and gut morphology of broilers from 0 – 14 days of age. Birds were fed diets containing 20, 23, or 25% protein and 3000, 3200 or 3400kcal/kg metabolisable energy using a 3 x 3 factorial design from 0 – 14 days of age. From 15 – 28 days all the birds in the experimental units were fed a standard diet to investigate the residual effects of the early protein and energy levels. There were significant interactions (P<0.01) between dietary protein and energy content in feed intake, weight gain and feed/gain ratio (P<0.01). At 20 and 25% protein level, increase in dietary energy levels above 3200kcal/kg resulted in a significant decrease in feed intake (P<0.01). At 23% protein, feed intake at 3200kcal/kg was significantly lower than those of birds fed with either 3000 or 3400kcal/kg. At 20, 23 and 25% protein levels, increase in energy content above 3000kcal/kg resulted in a significant increase in weight gain (P<0.01). At 20 and 25% protein levels, increase in energy above 3000kcal/kg resulted in a significant decrease in feed to weight ratio (P<0.01). Significant interaction (P<0.01) also occurred on the residual effect of the dietary levels of protein and energy earlier fed to the birds on feed intake, weight gain and feed conversion ratio. At 20% protein level, increase in energy above 3200kcal/kg resulted in a significant decrease in feed intake, weight gain and feed conversion ratio. At 23% protein level, the feed intake and feed to gain ratio at 3400kcal/kg were significantly higher than those of birds earlier fed diets with either 3000 or 3200kcal/kg. 20% dietary protein level combined with energy content of 3400kcal/kg gave the lowest cost of feed cost/kg and cost of producing 1kg of the bird compare to dietary level of 25% protein and energy content of 3000kcal/kg which had the highest cost of feed/1kg and cost of producing 1kg of the bird. The diet of lower nutrient density (20% of protein level and 3400kcal/kg) showed a better cost – effectiveness when express as per kilogramme live weight.
Keywords: Broilers, Dietary Energy and Protein, Performance, Residual Effect.