CHAPTER I: LITERATURE REVIEW - Repository.lib.ncsu.edu

CHAPTER I: LITERATURE REVIEWABSTRACTLeg health is a worldwide concern due to welfare issues and high economic losses in thepoultry industry. Skeletal disorders are relevant welfare problems due to locomotionimpairment and bone fragility during handling of birds. In addition, leg health negativelyimpacts feed efficiency, growth performance, and increases late mortality in broilers. At theprocessing plants, speed of automatic processing lines and meat quality could be adverselyaffected by a high prevalence of leg problems. The most common leg problems are thedevelopmental disorders including valgus and varus deformities, tibial dyschondroplasia,crooked toes, spondylolisthesis, and rotated tibia. Lameness is also a predominant leg healthissue, which is measured by scoring willingness of the birds to stand and walk. Boneformation starts very early in life during incubation and is affected by nutrient bioavailabilityin the egg and gas exchanges through the eggshell. Genetics is still a major component of leghealth issue in broilers. However, some management or nutrition factors of breeders mayaffect leg health in the progeny. The two major diets formulated in the poultry industryworldwide, corn or wheat-barley based diets, have differences in some nutrient contentsincluding non-starch polysaccharides, macro and trace minerals, intrinsic phytase, vitamins,carotenoids, and fatty acids. The type of extension of feed restriction in broiler breedersduring rearing to production can also impact broiler progeny performance by changingproportionality of oviduct segments. In addition, feeder space change at photostimulation hasan impact on breeder reproductive efficiency and broiler progeny performance. Inconclusion, leg problems are common multifactorial disorders which are influenced not onlyby broiler management but also by breeder management and egg characteristics that impactincubation conditions for embryos.1