Dietary manipulation for reduced ammonia emission and tan in broiler litter

Three experiments were conducted to evaluate the efficacy of dietary manipulation on ammonia (NH3) and other gaseous emissions, broiler litter total ammoniacal nitrogen (TAN), litter pH and moisture content and broiler chicken performance. Dietary treatments consisted of four levels of crude protein (CP): a conventional High CP diet (Hi), a very Low CP diet (Low), and two intermediate CP diets (M-HI and M-Low) obtained by mixing the High and Low CP diets. Respective CP levels used in the grower and finisher diets were as follows: Treatment Hi - 23.0% and 22.5%; Treatment M-Hi - 20.8% and 20.0%; Treatment M-Low - 18.5% and 17.5%; and Treatment Low - 16.3% and 15.0%. All diets were formulated to the same minimum digestible amino acid (AA) levels in the ratios to lysine similar to those suggested by Baker (1994). Levels of threonine, tryptophan and arginine were increased slightly above minimum levels which had shown responses in previous studies (Hussein et al. 2000a; Baker, 1994). Experimental design consisted of 12 replications of each treatment, blocked by room ventilation quadrant. A pen of 24 birds (Avian males) was the experimental unit. Collected data included bird performance at 42 days; litter characteristics including temperature, pH, moisture content, total ammoniacal nitrogen (TAN), and equilibrium NH3 gas concentration at end of each trial; and bird carcass characteristics for the second experiment. Trial completion dates were August, October and December, with three weeks between flocks. Results of the first three trials to date indicate that a diet with reduced CP and supplemental AA may achieve satisfactory bird performance. Body weights at day 42, in Trials 1 and 2, were significantly heavier for Hi and M-Hi treatments compared with M-Low and Low treatments. In Trial 1, feed intake for Hi and M-Hi treatments were significantly greater but not in Trials 2 and 3. In all 3 trials, birds on the Low CP treatment had significantly poorer feed conversion; there was no difference between M-Hi and Hi diets. After three flocks raised on the same litter, pens for birds on the Hi CP diet exhibited significantly greater concentrations of equilibrium NH3 gas. Mean litter pH ranged from 6.90 to 8.78 over the three trials, with the Hi CP treatment having the highest pH and the Low CP diet having the lowest pH. While the diets used in this study are not yet optimal, they have demonstrated that lower CP diets can be used to control waste N and equilibrium NH3 gas.