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    Marine predation injuries in yellow-eyed penguins (Megadyptes antipodes) : a thesis presented in partial fulfilment of the requirements for the degree of Master of Veterinary Science in Wildlife Health at Massey University, Manawatū, New Zealand
    (Massey University, 2023) Johnson, Kathryn Louise
    Yellow-eyed penguins (Megadyptes antipodes), endemic to New Zealand and its subantarctic islands, are one of the rarest penguin species in the world, with many factors threatening their survival. Marine predation is one such threat to this species, affecting a large proportion of adult and juvenile yellow-eyed penguins each year across their mainland range. New Zealand sea lions (Phocarctos hookeri) have been witnessed attacking yellow-eyed penguins, however other predators have not been definitively determined. Sharks are suspected based on the characteristics of some wounds. Barracouta (Thyrsites atun) have been implicated in some of the attacks, but evidence supporting this hypothesis is lacking. A broken fragment of tooth found in a yellow-eyed penguin leg laceration, provides evidence of a shortfin mako (Isurus oxyrinchus) or porbeagle shark (Lamna nasus) attack, but with the tooth incomplete and molecular testing inconclusive, an exact identification could not be determined. An increasing frequency of yellow-eyed penguins admitted to veterinary hospitals for treatment of marine predator injuries has been observed in the last decade. Necropsy data shows a similar trend. Assessment of individuals admitted to wildlife hospitals revealed that 84% had moderate to severe injuries. Two thirds (66%) of treated individuals survived to release, and of these 49.1% were not resighted after release, 22.4% were resighted as non-breeders and 28.4% subsequently made breeding attempts post release. Injury recrudescence occurred in 5% of cases. More than 15% of yellow-eyed penguins were hospitalised for multiple predation attacks during the study. Prognosis was largely attributed to the presence of severe injury complications. Hospital survival was reduced by nine times with the presence of a tendon or ligament injury, seven times with nerve damage and three times with osteomyelitis. Complications secondary to captivity were observed in 51.5% of necropsied yellow-eyed penguins which died or were euthanised in veterinary or rehabilitation centres, with fungal and bacterial pneumonia and air sacculitis, and tracheal stenosis, identified as the most common diseases.
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    Investigating the pathogenesis of catastrophic humeral fractures in dairy heifers in New Zealand : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Veterinary Science at Massey University, Palmerston North, New Zealand
    (Massey University, 2022) Wehrle Martinez, Alvaro Sebastian
    Catastrophic outbreaks of spontaneous humeral fractures in dairy heifers in New Zealand have given rise to animal welfare problems and resulted in significant economic losses to the New Zealand dairy industry. Preliminary small sample size studies have identified potential causes and/or factors associated with the occurrence of humeral fractures including periods of protein-calorie malnutrition, increased osteoclastic bone resorption related to lactation, and low liver and/or serum copper concentration (suggestive of periods of copper deficiency). Nevertheless, outbreaks of humeral fractures still occur throughout New Zealand with devastating consequences. Therefore, the main objective of this thesis was to investigate the likely causes and/or major risk factors associated with the occurrence of spontaneous humeral fractures in dairy heifers in New Zealand and propose a likely pathogenesis of the condition. For this, a large cohort of bone samples (humerus and ribs), as well as liver and blood/serum samples were collected from 2-year-old dairy heifers that suffered spontaneous humeral fracture post calving (affected heifers) for comparison with age-matched post-calving heifers with no bone fractures (control heifers). Blood/serum samples, used for the determination of biochemical profile in affected heifers, showed increased B -hydroxybutyrate and decreased creatinine concentration indicative of negative energy balance and/or periods of undernutrition. Bone samples were used for gross, histologic, histomorphometric, Raman and Fourier transform infrared spectroscopic analysis as well as for the measurement of the collagen and collagen crosslink content in bones from affected heifers compared with control heifers. Histologically affected humeri had osteoporosis (reduction in trabecular volume with abnormal trabecular architecture, thicker growth plates with abnormal architecture, increased resorption in the distal humerus, and a thinner cortex with increased and abnormal resorption. Abnormal cortical resorption increased the probability of fracture 54.2 times and reduced trabecular density 249.5 times. Spectroscopic analysis indicated decreased bone quality in the humeri from affected heifers with a reduced amount of bone organic and mineral components, lower mineralisation, lower carbonate substitutions, increased bone remodelling, and reduced mineral crystallinity. Analysis of collagen content and collagen crosslinking using liquid chromatography indicated reduced total collagen content and increased collagen crosslinking in the humeri from affected heifers. Finally, a survey was conducted using farms that have and have not had a case of humeral fractures showed Holstein-Friesian Jersey cross breed was a possible risk factor. The likely causes and/or major risk factors associated with the occurrence of spontaneous humeral fractures in dairy heifers in New Zealand include breed, protein-calorie undernutrition during important bone growth periods (which significantly affected the bone chemical composition and architecture) and increased abnormal bone resorption. These factors have significantly compromised bone mechanical strength and led to the spontaneous humeral fracture.
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    Investigations of a novel retinal disease in Wiltshire sheep : a thesis presented in partial fulfilment of the requirements for the degree of Master of Veterinary Studies in Veterinary Pathology at Massey University, Palmerston North, New Zealand
    (Massey University, 2014) Hunt, Hayley
    In 2011 and 2012, nine cases of adult-onset blindness were identified in a single flock of Wiltshire sheep. Affected sheep typically developed detectable night blindness at 2 to 3 years of age, which progressed to complete blindness by 4 to 5 years of age. Opthalmoscopically, the disease was characterised by progressive tapetal hyperreflectivity and attenuation of retinal blood vessels, indicative of retinal thinning and atrophy. Retinal histology revealed a selective loss of rod photoreceptors in the early stages of the disease, with preservation of cone photoreceptors. Secondary loss of cone photoreceptors was seen later in the course of the disease. Retinal degeneration was not accompanied by any other ocular or central nervous system abnormalities. Progressive retinal degeneration targeting rod photoreceptors has not been previously reported in sheep, but this disease has several similarities to inherited retinal dystrophies in other species, particularly progressive retinal atrophy in dogs and retinitis pigmentosa in humans. The disease in sheep is thought to be inherited in either an autosomal dominant or autosomal recessive manner, although additional cases identified recently provide further support for an autosomal dominant mode of inheritance. Initial investigations into the molecular basis of the disease, using a comparative candidate gene approach, did not identify any exonic single nucleotide polymorphisms (SNPs) in the rhodopsin gene of affected sheep that would alter the amino acid sequence. Homozygosity mapping of affected sheep revealed an identical-by-descent region on chromosome 5, but none of the genes within or surrounding this segment were considered to be plausible candidate genes except for GPR98, which is associated with retinitis pigmentosa and sensorineural hearing loss in humans. Investigations into the inheritance and molecular basis of this novel retinal degeneration in Wiltshire sheep are continuing, as this disease may prove to be a useful model for retinal dystrophies in other species, including retinitis pigmentosa in humans.
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    A search for biomarkers of ovine pre-partum vaginal prolapse : a thesis presented to Massey University in partial fulfilment of the requirement for the degree of Doctor of Philosophy in Biochemistry, Massey University, New Zealand
    (Massey University, 2019) Brown, Stuart
    Ovine pre-partum vaginal prolapse (known as bearings in sheep) occurs within a few weeks prior to lambing and unless treated both ewes and unborn lambs will die. Rates of prolapse in New Zealand vary from 0.1 to 5% per annum, varying between season and farms and is a worldwide problem. Much research has been undertaken over many years to determine the cause of this condition but no clear etiology has emerged. In this study plasma samples were collected prior to prolapse occurring in order to determine physiological changes leading to prolapse. 650 ewes were ear tagged and blood sampled on one day prior to lambing, 28 of these ewes subsequently prolapsed. The date of occurrence and tag number of prolapsing ewes was recorded to enable a comparison of the plasma profile of prolapsing ewes and non-prolapsing ewes. An improved method for running sheep plasma on 2D gels was developed resulting in improved protein spot resolution along with a lower coefficient of variation for spot volume. Using this improved method samples were subjected to 2D DIGE (two dimensional differential in gel electrophoresis) to determine if there were differences between the two groups of ewes. One of the differences was in haptoglobin, a major acute phase protein in ruminants, in which some isoforms were upregulated approximately 3 fold prior to prolapse occurring. This may indicate an inflammatory response due to either infection or injury. A good correlation was found between total haptoglobin spot volume data and quantitative haptoglobin assay data from the same samples (r² = 0.91) validating the haptoglobin gel spot data. Another finding was that alpha-1B-glycoprotein was down regulated close to prolapse, however the biological significance of this is unknown. It was also found that there was a negative correlation between cortisol and days to prolapse from sampling (r² = 0.36) i.e. ewes closest to prolapse had higher plasma cortisol concentrations than controls. These findings in conjunction with a literature search, field observations and an argument from logic lead the author to propose that chronic stress or anxiety may raise intra-abdominal pressure and contribute to the development of prolapse.