Effects of dietary forage on feed efficiency of poultry from a slow-growing and a dual-purpose strain for organic fattening systems

Dual-purpose chickens are increasingly used in European organic poultry systems. To test whether lower feed conversion efficiency of dual-purpose chickens could be counterbalanced by less intensive feeds with higher proportions of dietary fibre, a slow-growing conventional broiler genotype (Hubbard JA 757) was compared with a newly developed dual-purpose breed (Coffee ÖTZ), regarding their performance on diets with either low fibre (162 g kg−1 NDF) and high protein (217 g kg−1 CP; diet CON) or high fibre (256 g kg−1 NDF) and low protein (188 g kg−1 CP; diet EXT). In two further treatments, additionally to CON low- or high-quality chopped lucerne hay was offered separately. Forty-eight chicks of each genotype were allocated to the four treatments and fattened over 69 days (conventional broilers) or 77 days (dual-purpose roosters). After slaughter, intestinal organs and digesta were analysed. Voluntary intake of hay amounted to approximately 2% of the total feed eaten. In both genotypes, diet EXT led to higher intake and lower digestibility compared to CON, with less difference in Coffee. Genotype influenced feed intake, growth performance, dressing percentage, and carcass composition, all proving higher efficiency for Hubbard. Feed conversion efficiency was higher in Hubbard. However, in Coffee CP efficiency decreased less and energy efficiency even increased between CON and EXT. Gizzard, small intestine and caeca were larger, and fibre digestibility was higher in Coffee. Short-chain fatty acids in caecum were influenced by genotype. In conclusion, the high-fibre diet appeared suitable to reach appropriate protein and energy efficiency for Coffee roosters.