Abstract
Sustainably produced poultry meat with consideration of animal health poses a challenge for broiler production. Low protein diets with high amounts of synthetic amino acids (AAs) like methionine (Met) are the consequence. In a five-week feeding trial, 360 broilers (Ross 308) assigned to four feeding groups were offered protein-reduced complete diets (starter: 20% crude protein (CP); grower: 18.5% CP; finisher: 17.5% CP), supplemented with essential AAs. The "MHA" group received DL-2-hydroxy-4-(methylthio) butanoic acid (DL-HMTBA; trade name: MHA®), groups "L" and "DL" the respective Met source in equivalent concentrations each exceeding the nutritional recommendations. "R-MHA" ("R" for "reduced") received the minimum required level (using MHA as Met source). Performance exceeded performance goals without differences between the groups. The average feed conversion ratio (FCR) amounted to 1.35. The carcass/body weight ratio of R-MHA was significantly lower (0.782) compared to DL (0.808) and L (0.809). Breast meat of R-MHA contained significantly more fat (144 g/kg dry matter (DM)) compared to L (104 g/kg DM) and significantly lower CP content (R-MHA: 838 g/kg DM; L: 875 g/kg DM). The results indicated possible improvement in slaughter yield by protein-reduced diets supplemented with L-Met, thus recommending further research focusing on the Met influence.