The effects of chronic handling on the incidence of leg abnormalities and several blood parameters in turkeys

The role of environment and management on leg abnormalities in meat-type fowl

Continuous light with 1 h of darkness at midnight is a common photoperiod for raising meat-type fowl. The logic behind the 1 h of darkness, usually provided between midnight and 0100 h, is to acclimate the birds to darkness in the event of a power failure. Increasing evidence from several research laboratories indicates that lighting regimens other than continuous light, such as intermittent or step-up lighting, can lower the incidence of leg abnormalities in meat-type fowl. Some evidence suggests that increased exercise contributes in part to the reduction in lameness due to lighting. Management can influence the incidence of leg and foot problems via effects on rate of gain, flooring systems, and litter moisture. Rapid weight gains have been correlated with tibial dyschondroplasia (TD), although more evidence is needed to determine whether other types of leg deformities, such as long bone distortion, are related to rapid growth rates. Using low intensity X-ray imaging (hand-held lixiscope), live breeders with TD lesions can be identified and the incidence of TD can be reduced in breeder flocks through genetic selection. In addition, turkeys can be selected for wider shanks to improve walking ability. Slippery surfaces should be avoided to prevent spraddled legs. With the exception of TD, broilers reared in cages have more leg deformities than floor-reared birds. Dry litter conditions can help prevent foot pad dermatitis caused by Staphylococcus aureus and other bacteria.

Relationship of high intensity step-up lighting to bone ash and growth plate closure of the tarso-metatarsus in turkeys

The reduced lameness observed in turkeys reared in a high intensity step-up (HISU) lighting programme as compared to a low intensity step-down (LISD) lighting regimen cannot be explained by differences in the inorganic matrix of the bone, because the proportions of bone ash, bone ash calcium, and bone ash phosphorus did not differ between lighting programmes. At 17 weeks of age, there was a significant difference in the proportion of closed growth plates in males reared on the HISU programme rather than on LISD lighting. These results support the hypothesis that HISU lighting reduces lameness by promoting earlier growth plate closure of long bones.

Adrenocortical adaptation to chronic intermittent stress in hemispherectomized pigeon

Hemispherectomized pigeons were exposed daily to electrical footshocks delivered for 15 sec, at the same hour, for 8 weeks. Serial blood samples were obtained through a chronic vascular catheter. The adrenocortical response to chronic intermittent stress was measured kinetically at one week intervals. The initial response including several successive peaks of plasma corticosterone progressively adapted: Late peaks disappeared and only the first one subsisted 12-14 min after stressor application; this first peak diminished in magnitude; furthermore, an anticipatory peak occurred, starting 14 min before stress. In pigeons lesioned in the anterior dorsomedial thalamus, the only response to the stressor was of the single peak (12-14 min) type without any development of anticipatory conditioned response. This phenomenon was consistant all over the experimental period. Thalamic-hypothalamic interrelationships may be suggested to provide neuronal loops that underlie the long lasting, pulsatile repetitive components of the adrenocortical response to acute stress and also the adaptative process of such a response to chronic intermittent stress, including a conditioned, anticipatory endocrine activation.

Effects of high intensity step-up and low intensity step-down lighting programs on the incidence of leg abnormalities in turkeys

Two trials were conducted to determine if a high intensity (20 lx) step-up lighting program would decrease the incidence of leg abnormalities in turkeys. The step-up lighting regimen was compared to a low intensity (2.5 lx) step-down lighting program. Toms were used in Trial 1 and both sexes were employed in Trial 2. Body weight, feed/gain ratio, and mortality of toms of Trial 1 did not differ significantly between lighting regimens. The incidence of leg deformities and the length of the tarsometatarsal bone were significantly decreased, whereas plasma androgen and testes weights were increased for toms of Trial 1 in the high intensity step-up lighting. The same trends were apparent for toms of Trial 2 with the exceptions that feed/gain ratios were adversely affected and testes weights were significantly lower for toms of the high intensity step-up lighting program. The performance of hens in the high intensity step-up lighting program of Trial 2 was affected adversely; however, incidence of leg abnormalities and length and width of the tarsometatarsus responded in the same manner as with toms. The results of this study indicate that a high intensity step-up lighting program can significantly reduce leg weakness problems in turkeys. Possible explanations for light stimulation reducing the incidence of leg abnormalities are through increased exercise and shortening of long bones.

Habituation of the corticosterone response of ducks (Anas platyrhynchos) to daily treadmill exercise

The habituation of the corticosterone response of ducks to treadmill exercise (1.1 km/hr 0 degrees incline for 60 min) has been determined over a 28-day period. In untrained birds 30 min of treadmill exercise resulted in a marked (P less than 0.001) increase in the basal plasma corticosterone level. After 60 min of exercise the corticosterone concentration remained elevated (P less than 0.001) in comparison with basal and control (nonexercised) levels but was less (P less than 0.01) than that at 30 min. Following exercise the concentration declined to basal levels within 60 min. After 7 days of daily training the peak (30 min) corticosterone response to exercise diminished by greater than 50% and was absent in birds trained for 21 days. This habituation of the corticosterone response may be due to adrenocortical stimulation by pituitary adrenocorticotrophin (ACTH) being reduced. As the stimulatory effect of ACTH administration (8 IU/kg) on corticosterone secretion does not habituate in birds treated daily (for 28 days), the reduced corticosterone response to exercise may be due to decreased ACTH release rather than to a reduction in adrenal ACTH sensitivity.

The effect of caponization and dietary 17 alpha-methyltestosterone on the incidence of leg abnormalities in turkeys

Six hundred and seventy-two male turkeys were raised according to standard management procedures from 1 day to 3.5 weeks of age. At 3.5 weeks of age, the poults were equally distributed among four treatment groups. One group was subjected to surgical caponization and a second to sham operations. Of the two remaining groups, one served as a control while the other received feed containing 110 ppm of 17 alpha-methyltestosterone. All birds were maintained under identical environmental conditions until 20 weeks of age. Capons demonstrated a significantly higher incidence of leg abnormalities than controls or testosterone fed birds but did not differ significantly from the shams. These data correlated well with the levels of plasma androgen in that capons had significantly lower levels of plasma androgen than controls or testosterone fed turkeys, but concentrations did not differ significantly from shams. Plasma androgen concentrations or percentages of leg abnormalities were not different among shams, controls, or testosterone fed birds. Body weights, feed/gain ratios, mortality, and plasma corticosterone were similar for all four treatment groups.