Determination of economic level of protein and Lysine in broilers diet

In order to determine the economic optimal level of crude protein and lysine (Lys) in broilers diet, an experiment was performed based on compeletly randomized design in a 5×2 factorial experiment, with 5 levels of crude protein (Cobb recommendation and ± 1 or ±2 percent point higher or lower than Cobb recommendation) and 2 levels of dietary lysine (5.8 or 4.8 percent of dietary protein level). Birds had ad libitum access to diets in starter (0-10 days of age), grower (10-28d), finisher 1 (28-42d) and finisher 2 (42-49d) periods. Feed intake and average weight gain were measured at the end of each period. Minimum feed cost per kilogram live weight and maximum profit was used for economical analysis of data. Different level of crude protein and Lys had significant (P<0.01) effects on feed intake, average weight gain (except of finisher 2 periods). Different level of protein had significant (P<0.01) effect on feed conversion ratio, while levels of Lys had not significant effect on feed conversion ratio. The interaction between different level of protein and Lys was significant on feed intake at starter period (P<0.05), weight gain in grower (P<0.05) and entire rearing period (P<0.01) and feed conversion ratio (P<0.05) in grower period. Economical analysis showed the accuracy and sensitivity of the maximum benefit. For maximising benefit, increasing the level of dietary protein more than two percent higher from Cobb recommendation was economically justifiable. Also, results showed that increasing dietary Lys up to Cobb recommendation is economically profitable, especially in low protein diets, but if protein content in diets be more than Cobb recommendation, use of NRC Lys recommendation can be beneficial.