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Effects of nutrition and UV lighting on broiler bone and leg abnormalities (broiler bones) - LK0660

Leg and gait disorders have been a considerable welfare problem for the broiler industry. Recent genetic, management and nutritional approaches have improved the situation but the battle is not yet won. More information is needed on nutritional factors regulating bone development, and their genetic interactions, to allow further improvements in current broiler welfare and assist breeders in developing more robust strains. There are numerous causes of leg bone abnormality, from specific lesions associated with tibial dyschondroplasia (TD) to unspecific distortions of longitudinal growth. Vitamin D metabolism has been shown to be involved in TD and recent findings suggest that inducing a high vitamin D status in young chicks, by feeding high concentrations of vitamin D, can markedly alleviate or prevent TD. Alternative means of inducing high vitamin D status, without recourse to supralegal levels of vitamin D, could include use of vitamin D metabolites, UV irradiation or maternal supplementation. Other regulatory factors also control bone development. Prostaglandins are an important class of bone regulatory factors synthesised from dietary n-3 and n-6 fatty acids. Dietary supplementation with n-3 fatty acids has been shown to promote bone development, but meaningful studies have not yet been carried out in broilers. The purpose of the project is to investigate the effects of these two important factors, dietary n-3 fatty acids and vitamin D, on bone development during the critical first two weeks of the chick’s development and on welfare over the production period. The specific objectives of the project are to (1) determine whether the dietary balance of n-3/n-6 fatty acids influences broiler bone development (2) determine whether there are carryover effects of maternal dietary fatty acid composition on the bones of progeny (3) determine effectiveness of vitamin D metabolites or high concentrations of vitamin D in broiler and breeder diets in preventing TD (4) investigate the effectiveness of UV irradiation as a means of enhancing vitamin D status of hatching chicks (5) investigate whether there are interactions between these factors. The project partnership put together to investigate these topics includes companies involved in the breeding, hatching and growing of broilers and in the supply of feeds and feed supplements. The project will provide information on new approaches to improving the sustainability of UK agriculture by providing novel approaches to improving broiler welfare. The source of n-3 fatty acids will be salmon oil; development of a market for this byproduct will improve the sustainability of the UK salmon farming industry.
A Determine the effects of dietary n-3/n-6 fatty acid content on bone development in broilers.
Nutritional studies will initially be carried out under laboratory conditions to determine the effects of different types of dietary fat (rich in n-3 or n-6 fatty acids or combinations) on bone development under normal conditions or abnormal conditions of Ca/P balance that might promote bone abnormality. Laboratory findings will then be evaluated under commercial conditions.
A1 Small-scale experiments to determine effects of dietary n-3/n-6 contents on structural and morphological characteristics of bones in young broilers.
A2 The optimum diet fatty acid combination(s) established in A1 will be evaluated under commercial conditions. Measurements will include performance and leg health characteristics over the production period.
Achievement of these objectives is highly likely.

B Determine the effect of n-3/n-6 fatty acid composition in the maternal diet on bone development of the progeny.
Studies on Objective B will be carried out on breeder birds on the premises of an industrial partner and bone assessments will be carried out on chicks reared under both laboratory and commercial conditions.
B1 A commercial flock of broiler breeders will be fed diets(s) of different n-3/n-6 content. Performance and hatch results will be monitored.
B2 Chicks from these breeders will be reared up to 2 weeks under laboratory conditions for assessment of bone structural and morphometric characteristics.
B3 Chicks from these breeders will be reared under commercial conditions for measurement of performance and leg welfare characteristics over the production period.
Achievement of these objectives is highly likely

C Determine the effective doses of vitamin D and vitamin D metabolites in chick and breeder diets to optimise bone development.
Laboratory studies will establish optimum dietary concentrations of vitamin D and 25-D to optimise bone development and prevent TD in broilers. Responses will be compared in different genetic lines. Breeder hens will be fed diets supplemented with high concentrations of vitamin D or 25-D and effects on chick bone development will be studied.
C1 Genetic effects on vitamin D requirements. Comparisons of responses in bone structure and morphology to different levels of vitamin D in a commercial and a pedigree broiler line.
C2 Effect of dietary calcium on vitamin D responses. Factorial experiment to measure bone structure and morphology in young broilers fed different dietary combinations of calcium and vitamin D.
C3 Effects of 25-D. Determination of responses in bone structure and morphology to 25-D in young broilers.
C4 Effects of breeder nutrition. Diets of small numbers of breeders will be supplemented with extra vitamin D or 25-D. Effects on vitamin D status and bone structure and morphology will be measured at 2 and 6 weeks.
Achievement of these objectives will depend in part on provision of pedigree birds from Aviagen. This is unlikely to be a problem.

D Investigate the effectiveness of UV irradiation of hatching chicks in improving subsequent bone development.
Irradiation studies on chicks will be carried out initially under laboratory conditions to establish optimum procedures (exposure times up to one hour, radiation intensity) and duration of responses. Procedures established will then be applied in a commercial hatchery and health and bone quality of chicks reared on commercial situations will be evaluated.
D1 Evaluation under laboratory conditions of procedures for UV irradiation of day-old chicks and effects on vitamin D status and early bone development. Achievement of this objective will have to take account of safety issues for eye health (human and bird).
D2 Evaluation of UV irradiation in commercial hatchery and effects on performance and leg welfare of commercial broilers. Achievement of this objective will depend on success in D1 and also establishment of procedures in the hatchery that are likely to be safe for human and bird eyes.

F Interaction between fatty acid and vitamin D factors
This objective will investigate whether there are any interactions between fatty acids and vitamin D status that might provide a further benefit to broiler leg health. Precise plans for this objective will depend upon results in the earlier objectives, but possible sub-objectives are:
F1 Interactions between dietary vitamin D content and fatty acid composition of broiler diet
F2 Interaction between UV irradiation and dietary fatty acids.

(iii) Scientific approach

Measurements of bone development/quality will include growth plate and cortical bone morphology and cellular characteristics, cortical bone composition and strength and metabolic markers of bone development routinely applied at Roslin. Procedures include (a) preparation of histological sections of growth plate and cortical bone and quantitative assessment of morphological characteristics by computerised image analysis, (b) measurements of bone 3-point breaking strength using a materials testing machine, (c) measurements of bone ash content, (d) measurements of blood ionised calcium concentrations. Measurements of plasma 25-D concentrations using commercial RIA kits will be used to monitor vitamin D status in chicks at different developmental stages. On farm leg health will be assessed by standard gait scoring techniques. Dietary fatty acid analyses will use GLC.
The UV irradiation procedures raise issues of eye health for birds and humans. The procedures at RI will be carried out using criteria for radiation safety for humans under the inspection of the Institute appointed Radiation Protection Officer. The experiments on birds will be carried out under a Home Office Licence specifying the allowable procedures. It is envisaged that the irradiation will be carried out from below on chicks placed on wire floors. Preliminary studies with chicks on wire floors have shown that at a high stocking density, as used during chick transport, the heads (and eyes) of the chicks are not visible from below for most of the time.
Irradiation under these conditions should thus minimise direct eye exposure to UV radiation. Using published information (Voke, 1999) on effects of intensity and duration of UV exposure, we have calculated that at the UV intensity likely to be used, eye exposures of up to 8 minutes would be safe. During the irradiation experiments, short-term effects of UV exposure on eye health (photokeratitis) will be tested by measuring pecking frequency at food to determine whether visual acuity has been impaired. Long-term effects will be assessed by histology of eyes. UV intensities will be measured directly. Conditions in the commercial hatchery will be monitored to ensure similar bird and human safety standards are achieved.
Project Documents
• Executive Summary : Effects of nutrition and UV lighting on broiler bone and leg abnormalities (broiler bones)   (3405k)
Time-Scale and Cost
From: 2004

To: 2007

Cost: £433,968
Contractor / Funded Organisations
Optivite Ltd, DSM Nutritional Products, P.D.Hook (Hatcheries) Ltd, Aviagen Limited, Roslin Institute, Edinburgh (BBSRC), Rossyew Ltd, BOCM Pauls Ltd
Animal Health              
Animal Welfare              
Livestock Farming