By Prof. Ross Gordon Cooper
Ostriches, chickens and turkeys are principally terrestrial, although they are certainly capable of great speed particularly during avoidance and defensive situations. It is essential that the farmer establishes the correct incubator temperature and relative humidity parameters if the development of the embryo is to proceed normally. In addition, the provision of nutritionally beneficial feed and organic matter, plus a clean supply of drinking water is absolutely essential for sustaining regular, uninterrupted growth, particularly of the limbs. Indeed, limb deformities and/or weaknesses are great sources of encumbrance to the birds and the producer.
Chickens – The primary reasons for impaired locomotion and poor leg health in chickens, are associated with high growth rates, factors including age of the bird, genotype, lack of whole-wheat in feed, reduced daylight hours, higher stocking densities, lack of antibiotic use, and feeding intact feed pellets. Some studies found that Relative Humidity was extremely important in the first week of the bird’s life as it influenced later health of the chickens. As locomotion will be affected by the overall health status of the chicken, efficient ventilation, drinkers, numbers of stockmen and litter type are all important. Motivation is the dominant determinative factor for walking in birds with a low body weight, and physical ability is the dominant factor for walking in birds with a high body weight. Indices of leg weakness in broilers vary considerably among commercial line crosses and include walking ability, tibial dyschondroplasia, foot pad burn, hock burn, and angulation of the hock joint. Tibial dyschondroplasia, involves abnormal cartilage development in the proximal end of the tibia, it occurs primarily in broiler chickens, and the incidence is higher in males than in females. A shorter photoperiod may affect walking ability and tibial dyschondroplasia, although body weight plays a greater role. Studies found that broilers feed on low protein diets and lighter diets with moderate or high protein concentrations. Interestingly; protein, sex or gait had no influence on bone parameters, bone strength being associated with skeletal weight and length. Red light exposure increased growth when provided at the beginning of the rearing period, although bone strength was reduced. Rearing chickens in bright red light increases activity and reduces locomotion disorders in the late rearing period. High stocking densities reduce activity in broiler chickens and birds stocked at a high density early in the rearing period are most active in the presence of people and show the longest immobility in response to stressful situations. Layers place their legs directly under the center of gravity resulting in the body moving in a straight line, whereas broilers move the center of gravity step by step laterally towards the position of the supporting leg. Limping in broilers with leg problems can be observed and measured in the lateral and vertical movements of the right and left leg.
Turkeys – The relatively poor relationship between muscle strain and running speed in turkeys reflect the fact that changes in running speed are non-associated with demands of mechanical work. At 18 weeks of age, turkeys spend a considerable proportion of time performing sexual courtship strutting. Other turkeys perform a running or frolicking behaviour, but rarely engage in dust bathing and ground-scratching whilst feeding. Lack of feather and injurious pecking may be attributable to low stocking densities of turkeys general. Crossing a turkey line selected for increased shank (the part from the knee to the ankle) width and commercial sire lines, results in improvements in movement and walking of turkeys within pens. Selection for increased shank width in turkeys with increased shank diameter, results in increases in the weight of the tibiotarsal and femur bones. Large genetic increases in body weight of male turkeys can be achieved without loss in walking ability by genetic increases in shank width. Selection for increased body weight in turkeys’ results in increased numbers of eating periods, decreased duration of walking periods, and greater fear responses. Additionally, the rearing environment affects drinking, eating and resting behaviour, as indicated by range-reared turkeys which has fewer drinking periods of increased duration and longer eating and resting periods than confinement-reared birds. The gait (manner of walking) of healthy turkeys includes a walk with perfectly symmetrical and repeatable hind limb movements. Lame turkeys exhibit bilateral, non-symmetrical, intermittent and non-systematic movements.
Ostriches – Ostriches can run up to 70 km/h. Tibiotarsal rotation is a significant problem in ostriches and in one study on its occurrence in ostriches aged 14 months, hens were able to run faster than cocks implying their easier escape from danger. The strong limb musculature of the ostrich is necessary to facilitate running and defence. Body roll and ab/adduction of the leg shifted the foot position of ostriches away from its turn direction, thus reducing the acceleratory-braking forces needed to prevent under- or over-rotation and aligning the leg with the ground reaction force. Selection of walking or grounded running at intermediate speeds favors a reduction in the metabolic cost of locomotion characterized by a shift in locomotor kinetics from an inverted-pendulum gait to a bouncing gait that lacks an aerial phase. When the ostrich adopts an aerial-running gait at faster speeds there is no abrupt transition in mechanical parameters or in the metabolic cost of locomotion. If a producer is experiencing limb deformities in his flock, they are likely to see great losses as affected ostrich chicks are unable to eat and drink effectively. Injuries can be sustained in limbs when the ostrich is entangled in inappropriately constructed wire fencing or, due to stress, or collides violently with a paddock wall. Occasionally severe tears may be observed in birds from protruding nails and bits of wire. Tibiotarsal rotation may also predispose birds to getting leg tumors in areas constantly being grazed during movement. The producer may experience considerable economic losses due to badly scratched and worn skin.