Holstein calves were photographed and measured over a period of 84 days to determine the feasibility of Image Analysis as a measurement tool. It was determined that the disparity between actual measurements and image analysis measurements decreased as the bone length increased, and that image analysis could be used to monitor growth successfully in large ungulates, using the length of certain bone. Image analysis was then used to evaluate growth in Holstein calves on two weaning programs (weaned early at six weeks of age and weaned later at eight weeks of age). Calves were weighed and photographed over a period of 224 days to determine the effects of weaning on skeletal symmetry. Weaning time did have an affect on the skeletal symmetry of the calves, with calves weaned earlier found to be more asymmetrical. The extent to which skeletal symmetry is affected by a stress is determined by the nature and duration of the stress. The growth and development of Thoroughbred foals was recorded and photographed for a period of 300 days and the relative asymmetry for bilateral traits was assessed. Thoroughbred foal growth correlated to statistics reported over the last twenty eight years. Asymmetry can be detected in growing foals using image analysis. Weaning stress produced some asymmetry that the foals were able to recover from. One can use highly correlated body weight and height measurements to produce a tool stud managers can used to monitor growth. In young training Thoroughbreds (between 18 and 24 months of age), no significant asymmetry was found in the forelimbs but the hind legs displayed asymmetry, which has interesting implications for training and for performance criteria in the racehorse. Tools can be produced to monitor the growth and development of Thoroughbred foals destined to race, which can improve their management and the duration of their racing careers. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2008.

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Call number: LD2668 .T4 1962 G67

Call number: LD2668 .T4 1978 Q47 / Master of Science

Call number: LD2668 .T4 1978 S44 / Master of Science

Call number: LD2668 .T4 1979 H37 / Master of Science

A series of experiments were conducted to investigate the regulatory mechanisms governing the absence of and the initiation of pulsatile pituitary LH secretion during the infantile and prepubertal periods of development in the bull calf. In the first experiment, patterns of hypothalamic GnRH secretion into hypophyseal portal vessels were measured in sixteen Holstein bull calves at 2, 5, 8 and 12 weeks of age. The results of this study correlated the attainment of an hourly rate of pulsatile GnRH release to the onset of prepubertal LH secretion. In the second experiment, nine Holstein bull calves were infused with exogenous GnRH (200 ng) on an hourly basis from 1 to 6 weeks of age. From this experiment, we were able to demonstrate that an hourly rate of pulsatile GnRH release stimulates the age-associated changes in the hypothalamic-pituitary axis necessary for initiating pituitary LH secretion during the transition from the infantile to prepubertal period of development.

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No description available.

No description available.