Browsing by Author "Corner, Rene Anne"

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    Exposure of ewes to stressors in mid- and late- pregnancy : postnatal effects on the ewe and lamb : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Animal Science at Massey University, Palmerston North, New Zealand
    (Massey University, 2007) Corner, Rene Anne
    This thesis set out to examine the effect of maternal undernutrition and exposure to stressors between pregnancy day 50 to 100 and 100 to 147 of pregnancy on the ewe and her lamb. The long-term effects of these stressors during pregnancy on lamb growth, plasma cortisol response to a stressor, metabolism, behaviour and future reproductive success were examined. Mid-pregnancy shearing The component of mid-pregnancy shearing that causes the increase in lamb birth weight is unknown. It was hypothesised that the increase in lamb birth weight was due to the stress response of the ewe to shearing. This work examined the effect of a range of stressors at approximately day 80 of pregnancy. These stressors included yarding, crutching and sham-shearing that may be components of the shearing procedure that produce a stress response. In addition, repeated stressors between day 74 and 106 of pregnancy including isolation, sham-shearing and exogenous cortisol injection were used to examine the role of a longer-term stress response on lamb birth weight. Mid-pregnancy shearing has consistently resulted in an increase in lamb birth weight, however all the other stressors investigated had no effect. Therefore, the hormonal stress response of ewes to shearing was unlikely to be the cause of the increase in lamb birth weight. Mid-pregnancy shearing also resulted in minor changes in ewe and lamb behaviour 12 to 24 h after birth. Shearing during pregnancy had no effect on the cortisol response of ram lambs to handling or castration however differences were observed between singleton- and twin-born lambs. Ewe nutrition during pregnancy Ewes mildly undernourished in between days 70 and 107 of pregnancy that were then provided with adequate nutrition between days 108-145 of pregnancy gave birth to lambs with similar birth weights as ewes well-fed during both periods. Therefore the effects of undernutrition on lamb birth weight can be minimised if undernutrition can be limited to the earlier period (day 70-107 and 108-147 of pregnancy). Mild undernutrition in both periods (day 70 – 145 of pregnancy), resulted in lambs that were lighter and that exhibited behaviours associated with a greater ‘drive’ to maintain contact with their dam than lambs born to ewes well-fed during the same period. This suggests that even mild undernutrition in both mid- and late- pregnancy should be avoided. The effect of maternal nutrition and lamb litter size on the behaviour of female offspring was examined at 1 and 2 years of age. Litter size had no effect on ewe behaviour at 1 year of age however at 2 years of age twin-born ewes had higher maternal behaviour scores than triplet-born ewe lambs. Nutrition of the maternal grand dam during pregnancy had only a minor effect on the behaviour of female offspring at 1 year of age and no effect on maternal behaviour at 2 years of age.
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    Two studies on the control of wildlife-derived tuberculosis : farmer views and model validation : a thesis presented in partial fulfilment of the requirements for the degree of Master of Veterinary Studies in Epidemiology at Massey University, Palmerston North, New Zealand
    (Massey University, 2002) Corner, Rene Anne
    The two studies included in this thesis are part of a larger research programme evaluating tools to aid in the eradication of bovine tuberculosis (TB) from cattle in New Zealand. The first study was a survey of farmer’s attitudes towards the National Pest Management Strategy (NPMS) and tuberculosis control. The second study validated the population component of PossPOP, a spatial stochastic simulation model of TB in a wild possum population. A postal questionnaire survey identified variation of attitudes of 404 farmers in four regions of varying TB status within New Zealand. Farmers were stratified by region, enterprise type, area TB classification and herd TB status. Of the farmers contacted by telephone prior to sending out the questionnaire 91% agreed to participate in the study and 83% of these farmers returned a completed questionnaire. The questionnaire contained questions on farmer demographics, TB status, herd TB history, farm management practices and attitudes towards the control of TB. Farmers with infected herds were generally positive about the control program and believed that TB could be eradicated from their herds. A number of farmers were concerned about proposed changes to the NPMS, such as the implementation of direct payment of TB testing costs by farmers and removal of compensation for infected cattle. An important finding was that the majority of farmers were not aware that the Animal Health Board was in charge of the NPMS. PossPOP was built using the first 22 months’ data from a longitudinal study of a possum population run at Castlepoint in the lower North Island of New Zealand. Data from the remaining 9 years of the study was used set for model validation. PossPOP was validated by comparing age distribution, sex structure and the proportion of births, deaths and immigrations in the modelled population against the field population. There was general agreement between the model and the field population and also published population patterns. PossPOP produced a stable population over time at different densities, with similar temporal patterns to the field population. Emergent biological properties were examined, such as rate of population rebuilding after a major population cull, the removal of immigration from both populations and age specific mortality. The field population grew much more rapidly following a cull compared with the PossPOP population due to home range expansion of possums that were living on the periphery of the study site, which was not programmed into the model. These results showed that while PossPOP models a small area, it reflects patterns of control over large areas making it a useful tool to evaluate large scale possum control strategies.