Modern poultry are afflicted by a variety of skeletal disorders that result in discomfort or pain and are a source of severely depressed welfare for the birds. Leg deformities are widespread in growing broilers and turkeys, osteoporosis results in broken bones in older laying hens and mature breeding birds can experience severe cartilage degeneration in the hip joint.
The projet will study the aetiologies of these disorders with the objectives of establishing procedures that may be applied in the short term to alleviate the severity of the conditions and to identify strategies that in the longer term may result in prevention.
Genetic and mnutritional strategies for minimising tibial dyschondroplasia(TD), an important factor in developmental bone deformaties in broilers, have been identified. Lesions can be detected radiographically in live birds and selective breeding can decrease the incidence in flocks. It is unlikely that predisposition to TD can be eliminated in this way. TD can be prevented nutritionally by the addition of a vitamin D metabolite to the feed. An interaction between 1,25-DHCC and dietary calcium can lead to growth depression. to avoid this, a maximum dietary concentration of 2 ug 1.25-DHCC per kr is recommended. Addition of phytase to the diet can enhance phosphorus availability for bone formation, and to minimise pollution. Practical application of these genetic and nutritional procedures should result in important improvements in the welfare of broilers through the alleviation of crippling leg disorders.
A survey of European laying hen flocks showed that bone fractures occured in 26% of birds. The main cause of this is the increased bone fragility through osteoporosis. The development of osteoporosis was found not to be prevented by improvements in nutritional practices. Modifications to the stocking or design of traditional cages had little impact on osteoporosis, but keeping birds in more extensive aviary type systems resulted in an improvement of bone quality. This was reflected in much lower variation in individual end of lay bone quality and lack of relationship between bone quality and egg productivity suggests that a genetic solution to the problem of osteoporosis may be possible.
The experiments will involve studies on the nutritional, genetic, environmental and cellular factors that influence abnormal bone growth in broilers. The occurrence of bone breakage in hens will be surbeyed in the participating countries and structural characteristics of bones will be compared. Housing, environmental, nutritional and metabolic factors affecting bone strength and structure will be identified. The causes and prevention of hip degeneration in turkey and broiler breeders will also be studied.
BS18 7DY Bristol