Feed efficiency, growth performance, and carcass characteristics of a fast- and a slower-growing broiler hybrid fed low- or high-protein organic diets

摘要

Organic poultry meat production in Sweden is characterized by diets based on organic and locally produced feedstuffs, roughage allowance, a long rearing period (>10?weeks), outdoor access for the birds, and ban of synthetic amino acids and prophylactic use of antibiotics and anthelmintic. Until recently, the main hybrids used in organic broiler chicken production in Sweden were the same as used in conventional broiler chicken production. These birds are bred to reach market weight at 5 to 6?weeks on a high-protein quality non-organic diet. In this study, organic high- and low-protein diets were fed to fast- and slower-growing hybrid broiler chickens with 5 pens per genotype × diet treatment and 21 to 22 broiler chickens per pen. Weight gain, feed conversion, health, and mortality were recorded during a 71-day rearing period. The fast-growing hybrid birds grew faster (55.4?±?0.7 versus 38.3?±?0.5?g/day, P ?=?0.001) and had a better feed conversion ratio (2.6?±?0.1 versus 2.9?±?0.1?kg feed/kg body weight, P ?=?0.001) than the slower-growing hybrid birds. The fast-growing hybrid birds grew slower when fed the high-protein compared to the low-protein diet (55.3?±?0.5 versus 57.8?±?1.4?g/day, P ?=?0.050), while the slower-growing hybrid birds grew faster when fed the high-protein compared to the low-protein diet (39.4?±?0.7 and 37.2?±?0.4?g/day, P ?=?0.038). A higher proportion of fast- compared to slower-growing hybrid birds had sticky droppings at 1?week of age (18.8?±?1.6 versus 3.8?±?1.6%, P ?=?0.001) and were culled because of leg weakness during the 10-week rearing period (10.0?±?2.0 versus 3.3?±?2.0%, P ?=?0.031), indicating poorer welfare among fast-growing hybrid birds when reared for 10?weeks on organic diets.