Colin C. Whitehead

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1. Heritabilities of a range of morphometric, radiological and strength characteristics were measured in the bones of end-of-lay hens. 2. Tibial strength (TSTR), humeral strength (HSTR) and keel radiographic density (KRD) were moderately to strongly inherited and were combined in a Bone Index which was used as a basis for selection. Data are available on 6(More)
The effects of dietary 1,25-dihydroxycholecalciferol on the incidence and severity of tibial dyschondroplasia (TD) were assessed in broiler fowl selected for TD (high-TD line) and against TD (low-TD line). Assessment was by examination with a portable Lixiscope to identify lesions in live birds, gross pathology and histopathology. Eighty broilers in four(More)
1. The effects of different dietary concentrations of vitamin E (alpha-tocopherol acetate) were investigated in 2 experiments on laying hens exposed to chronic heat stress at 32 degrees C. 2. In the first experiment, egg production and plasma concentrations of calcium and egg yolk precursors were measured in 24 hens before, during and after a stress period(More)
In young pullets, long bones elongate by endochondral growth. Growth plate chondrocytes proliferate, then hypertrophy, and are replaced by osteoblasts that form a network of trabecular bone. This bone is gradually resorbed by osteoclasts as the bone lengthens. Long bones widen, and flat bones are formed, by intramembranous ossification in which cortical(More)
1. Bone structure and breaking strength were measured in hens that had been housed throughout a laying year in battery cages or in Perchery, Naturel or Litter and Wire husbandry systems. 2. Battery caged hens had the poorest bones, as assessed by measurements of cancellous bone volume, radiographic density, cortical thickness and three-point breaking(More)
Osteoporosis in laying hens is a condition that involves the progressive loss of structural bone during the laying period. This bone loss results in increased bone fragility and susceptibility to fracture, with fracture incidences of up to 30% over the laying period and depopulation not uncommon under commercial conditions. A major cause of osteoporosis is(More)
1. The effects of different dietary concentrations of vitamin E (alpha-tocopherol acetate) were investigated on laying hens exposed to chronic heat stress at 32 degrees C from 26 to 30 weeks of age. 2. Diets containing 5 dietary concentrations of vitamin E (a control diet containing 10 mg alpha-tocopherol/kg or this diet supplemented to contain 125, 250,(More)
The course of tibial dyschondroplasia (TD) was followed in 20 broiler fowl fed ad libitum. TD initially developed between 2 and 5 weeks of age in all the birds. Tibial plateau angles (TP degrees ) were measured in the radiographs and used as an assessment of tibial bowing. There was a significant correlation between abnormal TP degrees and the age of onset,(More)
1. Two experiments were carried out to investigate responses in performance and bone compositional and structural characteristics in broilers fed diets containing 4 concentrations of vitamin D3 (5, 20, 125 and 250 microg cholecalciferol/kg) at different concentrations of calcium, available phosphorus and vitamin A. 2. In experiment 1, body weight and tibia(More)
The pathologies in proximal femora of broilers with lameness attributed to disorders of the proximal femur, including so-called 'femoral head necrosis', are described. Samples were collected from a variety of flocks, farms and production systems. Ten 'normal' broilers were also examined. Birds were identified by a characteristic lameness whereby they used a(More)