The effect of feed crude protein content and feed form on broiler performance, litter quality and ammonia concentrations

Nitrogen (N) excreted by poultry is converted to ammonia (NH3) by microbial enzymes and is influenced by temperature, pH, moisture and N content of the litter. NH3 presents an environmental risk and a health risk to the farmer and animals. Reducing dietary crude protein (CP) can effectively decrease N excretion in broilers provided that amino acid (AA) requirements are met. Feed form (mash vs. pellets) influences the development of the gastrointestinal tract, feed and water intake and therefore the N and moisture content of the excreta. This study investigated to which extent feed form and CP reduction can influence performance, litter quality and NH3 volatilised from litter of 2232 Ross 308 male broilers. CP was reduced by 1.5 and 3.0% from 20.5% in the grower and 19.5% in the finisher. Digestible AA:Lysine ratios were maintained by supplementation of synthetic AA. Each treatment was fed in mash and pellet form, leading to a 3×2 (CP level x feed form) experimental design with six treatments, each with six replicates. Mash diets or pellets with a 3.0% CP reduction led to lower feed intake (P<0.05) and growth (P<0.01) from 28 to 38d. Compared to pellets, mash resulted in better litter quality and a lower occurrence of foot lesions. Reducing CP by 1.5 and 3.0% decreased NH3 concentrations measured at litter level with a passive flux chamber method at 30 and 38d (P<0.001). These results suggest that pellets lead to better performance and reducing CP by 1.5% decreased NH3 volatilisation without compromising bird performance.