This introductory, review presentation is a prologue to four full-length symposium presentations. Estimates of the annual cost of skeletal problems in poultry and definitions of noninfectious skeletal diseases in poultry are the focus of this article. Losses due to skeletal problems in poultry are caused by an increase in mortality and the number of cull birds, increased condemnations from septicemia-toxemia, and more downgrading from the trimming of breasts and legs. Reduced feed conversion and rate of gain also occur. Estimated annual losses in the United States due to skeletal problems are $80 to $120 million in broilers, and $32 to $40 million in turkeys. Eleven skeletal problems in poultry are described, and synonyms, symptoms, and possible causes of each are presented. These diseases include long bone distortion, tibial dyschondroplasia, rickets, spondylolisthesis, degeneration of the femoral head, spraddled legs, chondrodystrophy, osteomyelitis and synovitis, Mycoplasma synoviae infection, viral arthritis, and footpad dermatitis.

Two experiments were conducted to determine linear growth and mineral deposition in the tibiae of Vantress x Arbor Acres broilers. In Experiment 1, birds were maintained in battery brooders for 21 days then housed in floor pens from Day 22 to 70. In the second experiment, birds were reared either in battery brooders and grow-out cages or floor pens from Day 1 to 63. Males and females were maintained separately. Birds in both trials were weighted at weekly intervals and three birds of each sex per treatment were euthanatized weekly to obtain tibia samples. Tibiae were cleaned of muscle and connective tissues, dried, extracted with diethyl ether, measured for length in centimeters, weighed, and ashed. Results from both experiments show a curvilinear response for weight gain, bone length, and bone ash weight. In some cases, sex by week or week by rearing interactions (P less than .001) were observed. As expected, males had greater weight gain and bone length than females. In Experiment 2, birds grown in floor pens had greater (P less than .05) bone length, tibia weight, and tibia ash weight than cage-reared birds, but percentage tibia ash was not different between the two rearing systems. Tibia growth and mineral deposition were influenced by gender and rearing systems. Bone ash weight data for females in both trials had a response curve that approached a sigmoidal shape. Response curve for males tended to be more quadratic, indicating a significant (P less than .003) week by week by sex interaction. Thus, there was evidence for bone growth differences not only between rearing systems, but also between sexes, the latter not unexpected.

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