Deliverables
One experiment was designed to determine the effects of TD on skeletal morphometry and gait, sampling six different strains of widely varying size and conformation throughout the growth period. TD had no significant effects on skeletal morphometry; there were no significant differences in tibial plateau angle, femoral, tibial, or tarsometatarsal torsion, length or circumference between birds with and without TD. Gait parameters collected from videotape and pedobarograph were similarly unaffected by the presence or severity of TD lesions. Tibial dyschondroplasia in turkeys was therefore considered to have no primary welfare consequences. In an experiment designed to determine if there were secondary welfare consequences of TD for growing turkeys, the results indicated that although TD appears to be associated with the development of osteomyelitic lesions in a small proportion of TD -affected birds, there appears not to be any major welfare problem associated with this secondary pathology because gait and behaviour were unaffected.
Three experiments investigated the role of selection for increased growth rate and altered conformation on gait and skeletal morphometry, using either objective, quantitative gait analysis and skeletal morphometry techniques, or subjective scoring methods. The results of all three studies indicated that selection for increased growth rate and altered conformation had significant effects on both skeletal morphometry and gait in growing turkeys. However, because behaviour was unaffected, it was concluded that there was no clear evidence that the altered gait and skeletal morphometry caused by selection had negative consequences for turkey welfare. Growing turkeys provided with environmental enrichment such as elevated platforms, straw bales and outside areas use them without any negative impact on performance parameters.
Three separate experiments investigated differences in TD incidence and severity between strains differing greatly in growth rate and conformation, whose body weight at 18 weeks ranged between 6.5 and 20kg and breast muscle mass as a proportion of body weight ranged from 17 -30%. The results indicated that TD occurred at an exceptionally high incidence across all turkey strains examined and peak incidence was similar (approximately 80%), in the commonly used commercial hybrid strain and the unselected Nebraska Spot strain. TD therefore appeared not to be influenced by selection for production traits.
A series of six experiments were conducted to determine the influence of sex, environmental temperature, light regimen and intensity and some nutritional factors on the development of TD in growing turkeys. Although TD incidence was high in both males and females, the incidence for males was significantly greater. TD incidence was not affected by light regimen or intensity, early qualitative feed restriction, dietary supplementation with 25(OH) D 3, or environmental temperature.
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