The Effects of Microbial Phytase to Low-Protein Diets Supplemented with Individual Amino Acids on Performance and Carcass Characteristics in Broilers

A 6 weeks experiment with 450 unsexed, one day-old broilers was carried out to determine the effects of adding phytase to low-protein diets supplemented with individual amino acids on performance, carcass traits and some organ weights. The chicks were fed with diets containing 22 and 20% Crude Protein (CP; control) for the 0-3 and for the 4-6 weeks of period, respectively. During the 0-3 and 4-6 weeks of periods, the other groups were fed with low protein diets (20 and 18% CP, respectively) containing lysine, methionine and threonine (EAA) levels of 100, 110, 120, or 130% of NRC recommendation. The diets were then supplemented with (500 FTU kg(-1) of diet; Natuphos, BASF, Germany) and without additional microbial phytase. This resulted in 4x2 factorial arrangements with four levels of and two levels of phytase (0 and 500 FTU kg(-1)) and so a total of 9 treatments with a control group were tested. Each treatment was replicated 3 times with each replication consisting of 15 chicks. All other nutrient contents of diets were met the requirements by NRC recommendation and were contained 3200 kcal ME kg(-1). The effects of interactions consist of EAA and phytase levels on body weight gain, feed intake, feed conversion ratio, carcass traits except for wings weight and relative organs weight had no significant (p>0.05). There were no main effects of dietary EAA levels on body weight gain, feed intake, feed conversion ratio, all measured carcass traits and relative organs weight, except for pancreas weight, in the experiment. As a main factor, effects of dietary phytase levels on all parameters had no significant. Also, there was no significant difference in terms of performances, carcass traits and organ weights (body weight (%)) between control diet and low-CP diets. These data suggest that broilers fed low CP, EAA supplemented diet (lysine, methionine, threonine levels of 100% NRC recommendation) have performance and carcass traits similar to broilers fed higher level of CP recommended by NRC.