Tibial dyschondroplasia (TD) results from a defect in endochondral ossification and is characterised by an accumulation of avascular cartilage extending distally from the growth plate. The lesion develops in young fast growing birds (broilers and turkeys) and is thought to be a result of incomplete chondrocyte differentiation. This condition can result in deformed bones and lameness and has therefore many economic and welfare implications.

Since its description 25 years ago, TD has been studied extensively. The majority of the research has focused on determining the role of nutrition in the aetiology of the disease but it has only recently been shown that this disorder can be completely prevented by supplementing the diet with 1,25(OH)2 D3 (Rennie et al., 1993).This may be related to the hormones ability to increase the rate of chondrocyte differentiation (Farquharson et al., 1993). Since ascorbic acid (AA) has been shown previously to stimulate the endogenous synthesis of 1,25(OH)2 D3 (Weiser et al. 1988), its effect on the development of TD in young fast growing broilers was investigated

Leg disorders in male turkey breeding stock are associated with pain during locomotion (Duncan et al 1990). Musculo-skeletal diseases are prevalent in broiler breeder males and the experiment was designed to evaluate birds of two ages for evidence of pain during movement. Two experiments were conducted, the first examined differences in sexual motivation and the second the rate of walking towards a food reward. At the end of the experiment the birds were killed and the legs dissected to establish the presence of musculoskeletal disease.

Commercial broiler breeder males were housed singly with 15 females in 4 rooms each containing 12 floor pens measuring 1.5 x 2.4 m. There were 24 males in each of two age groups (40 and 60 weeks at the start of the experiments). To determine sexual motivation, males were removed to an empty pen in a spare room. They were returned after 3-5 h and observed for 15 min. The time to make a sexual approach (AP) and to mount a female (MT), and the number of copulations were recorded on three different days. Subsequently, males were trained to walk through a 20 m long alley constructed of hardboard to receive their daily food allocation. During testing, the time taken to reach the food was recorded 3 times before the male was returned to its pen. The males in two rooms were used in a 2-period crossover experiment to evaluate the effects of naloxone (an opiate receptor antagonist) and three analgesics on walking speed (Table 1). All measurements of time were transformed to natural logarithms for analysis. A censored analysis was used for AP and MT. The total number of copulations observed (COP) was modelled using Poisson errors. The models included effects for age and day (where appropriate). The data were reanalysed with the lesion score as a fixed effect. The initial model for walking speed included period and carry over effects. Mixed model methods (REML) were used to assess the final model with birds as blocks and treatment and lesion as main effects.