Abstract:
This experiment was conducted to investigate the effect of protein reduction and substitution of cassava for corn on growth performance, ileal protein digestibility and nitrogen excretion in the feces of broilers. Total 2,688 day old male (Cobb 500) broilers were randomly divided into 8 groups with 6 replicates of 56 birds each. The 2 x 4 factorial arrangements were applied to perform 8 diets with 4 protein levels (100%, 95%, 90%, and 85% of primary breeder recommendation during 1-21 and 22-42 days of age) and 2 energy sources (Corn; CO and Corn substituted with Cassava 50%; CC) while maintaining a constant level of 4 essential amino acids (Met, Lys, Thr, and Trp) to meet the recommendation in each period. At 1-21 days of age, there were no effects from energy sources and interaction between protein levels and energy sources on growth performance. Protein levels affected on both FCR and nitrogen excretion but did not influence ileal protein digestibility. The 85% protein group had significantly higher FCR (P<0.05) than other protein groups, while fecal nitrogen decreased as dietary protein levels declined (P<0.05). At 22-42 days of age, there was interaction between energy sources and protein levels on feed intake. Birds in CC group had significantly higher FCR than CO group (P<0.001) and also found the difference in protein levels. Broilers fed the lowest protein level diet had significantly lower ileal protein digestibility and nitrogen excretion than other protein groups (P<0.05). Birds fed CO diets had significantly higher protein digestibility than CC diets (P<0.0001). In conclusion, dietary crude protein can be reduced up to 95% of recommendation and cassava can be used to substitute for corn by 50% when considered only growth performance and economic returns. However, when environmental pollution was included, the crude protein could be decreased to 90% of recommendation.
