THE EFFECT OF DIETARY-PROTEIN AND PHOSPHORUS ON AMMONIA CONCENTRATIONAND LITTER COMPOSITION IN BROILERS

An experiment was conducted to determine whether broiler litter concen tration of N and P and equilibrium NH3 gas concentration can be reduce d by reducing dietary CP and P levels and supplementing with amino aci ds and phytase, respectively, without adversely affecting bird perform ance. Equilibrium NH3 gas concentration above the litter was measured. The experiment was divided into a starter period (1 to 21 d) and grow er period (22 to 42 d), each having two different CP and P levels in a 2 x 2 factorial arrangement. The CP treatments consisted of a control with a mean CP of 204 and 202 g/kg for starter and grower periods, re spectively, and a low CP diet with means of 188 and 183 g/kg, respecti vely, but with similar amino acid levels as the control. The P treatme nts comprised starter and grower control diets containing means of 6.7 and 6.3 g/kg P, respectively, and low P treatment means of 5.8 and 5. 4 g/kg P supplemented with 1.0 g/kg phytase. Reducing starter diet CP by 16 g/kg reduced weight gain by 3.5% and, hence, body weight at 21 d of age, but did not affect feed intake or feed efficiency. Reducing P did not affect feed intake and weight gain, but improved feed efficie ncy by 2.0%. Responses in feed intake and efficiency to CP depended on the level of dietary P. For the grower period there were no significa nt differences in feed intake, weight gain, and feed efficiency, nor i n body weight at 42 d of age, after correcting for 21-d body weight, b etween CP and P treatments. There were significant (P < 0.001) reducti ons in litter N and P concentrations, but not equilibrium NH3 gas conc entration, moisture content, or pH, for low CP and P diets. Mean equil ibrium NH3 gas concentration was 63 ppm. Litter N concentration was re duced 16.3% with the low CP diets, and litter P by 23.2% in low P trea tments. The results suggest that dietary manipulation shows merit for reducing litter N and P concentrations while maintaining acceptable pr oduction performance from broilers.