Protein supply in organic broiler production using fast-growing hybrids : welfare and performance aspects

Sammanfattning: The broiler's requirements of sulphur amino acids (AA) are high; however, currently available organic protein feedstuffs generally contain only low levels. According to national organic standards, fast-growing broilers in organic production are allowed to be slaughtered at 70 d, provided that their average growth rate does not exceed 50 g/day. This means that a growth restriction is necessary and may be done by using a low crude protein (CP) diet. However, such organic diets imply a risk for low dietary AA levels, which may jeopardize poultry welfare. The aim of this thesis is to evaluate the effect of organic, low CP/AA diets on bird welfare and to evaluate the use of hemp seed cake as a potential future protein feedstuff in organic diets. Three experiments were conducted over production periods of 70 d both indoors and in organic outdoor productions. The experiments covered evaluations of behaviour, health, physiological indicators and production when feeding fastgrowing broilers low CP and AA diets, also with the inclusion of hemp seed cake. Birds fed low CP/AA diets had lower live weights, increased activity, decreased mortality, and fewer birds had to be culled due to leg problems compared to birds fed higher levels of CP/AA. However, observed behavioural differences indicated that birds fed the low CP/AA diet showed hunger and associated frustration. These birds used their outdoor pasture much more, and had a higher forage intake, indicating a search for other nutrients than the ones provided. Cannibalism occurred in birds fed the low CP/AA diets, which is a welfare risk with such diets. Even though mortality was lowered for these birds, overall it was high and culling due to leg problems occurred during the last three weeks. The results indicate that low CP/AA diets used to maintain a maximum growth of 50 g/day are not optimal regarding bird welfare. The use of female broilers in organic production could be advantageous, to further reduce growth rates and culling due to leg problems. Another solution may be to shorten the rearing periods by approximately three weeks. The use of hybrids with lower growth rates may be an alternative in Swedish organic production and needs to be evaluated.