Massey Documents by Type

Permanent URI for this communityhttps://mro.massey.ac.nz/handle/10179/294

Browse

Subject: search.filters.subject.VETERINARY MEDICINE

Search Results

Now showing 1 - 10 of 29
  • Thumbnail Image
    Item
    Ovine paratuberculosis : transmission dynamics and cost-effectiveness of interventions : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy at Massey University, Institute of Veterinary, Animal and Biomedical Sciences, Palmerston North, New Zealand
    (Massey University, 2017) Marquetoux, Nelly
    This thesis aimed at enhancing the knowledge about the epidemiology and control of paratuberculosis caused by infection with Mycobacterium avium subsp. paratuberculosis (MAP) in the New Zealand farming system, with a primary focus on sheep. The potential for pathogen transmission between farms was explored in two studies. Four years of livestock movement records to and from 112 corporately owned farms in New Zealand, involving 1.15 million sheep, cattle and deer were analysed using social network analysis. In the first study, topologic features favouring pathogen spread in this network of farms were established. Hub-farms were identified as targets for risk-based movement control strategies to effectively decrease the potential for large epidemics. Inferences about movement control were not specific to MAP, so could apply to any pathogen transmission. In a second study, the potential for MAP transmission between farms was evaluated. In 2010, cross-sectional MAP screening using faecal culture and genotyping of cultures was performed on a subset of 102 farms in this network at the herd/flock level. These data were merged with the data about livestock movements. Multiple regression methods adapted to network data showed associations between past livestock movements and current strain type distribution in this population of farms. Farms in the same livestock movement network community were found to be twice as likely to share the same strains of MAP compared to farms in different communities (p=0.033). These studies showed that livestock movements between farms favour pathogen transmission and likely contribute to the high level of MAP infected farms in New Zealand. Results suggest that MAP can establish in a flock following the introduction of infected animals, and that biosecurity applied to trade may reduce the spread of MAP. In a second part, a compartmental infection model was developed to simulate paratuberculosis on a typical self-replacing Romney sheep farm in New Zealand. This was preceded by a review of the literature on the physio-pathology of MAP infection in sheep, clinical outcomes and pathways following MAP infection to inform the model structure. A review of MAP enumeration methods in vitro identified comparative biases in estimating MAP doses in experimental studies. Subsequently, a systematic review and meta-analysis of experimental infection of sheep with MAP quantitatively estimated parameters for the simulation model, and identified relevant challenge-dose effects. The meta-analysis also enabled to integrate the effect of age at exposure, strain of MAP and type of inoculum on the outcomes of experimental infection with MAP. It determined that MAP is highly infectious, with only 76 live ingested organisms required to cause histological lesions in the small intestine in 50% of inoculated sheep. However, 8.9 x 106 MAP organisms were necessary to cause progression to clinical disease in 50% of sheep infected as lambs or hoggets, and 7.7 x 109 in sheep infected as adults. Simulations using the model were carried out for a range of clinical incidence scenarios, to study the impact of ovine Johne’s disease (OJD) on a New Zealand pastoral sheep farm and the cost-effectiveness of interventions, e.g. vaccination. The impact of OJD is low on the majority of NZ pastoral sheep farms. These would not economically benefit from vaccination. However, vaccination with GudairTM drastically reduced OJD mortality in flocks with high (1%) to very high (2%) annual clinical incidence of OJD in ewes, and was cost-effective. At a level of 1% OJD cases/annum in the ewe flock, the time to positive return on investment was 23 years, dropping to five years for 2% OJD cases/annum. After 30 years, farms with 2% OJD could expect NZD 2.4 return (net present value) for each dollar invested, with a total net profit of NZD 2,435 per 100 ewes in the flock. Meat price fluctuations had a strong impact on the economic evaluation. Besides, annually replacing 1% of the flock with infected ewes tended to negate the beneficial impact of vaccination on reducing clinical disease incidence, through maintaining high levels of pasture contamination. The movements of MAP-infected animals can thus jeopardize the success of vaccination strategies. In the current context of high endemic prevalence of MAP infection in New Zealand farms, and given evidence about transmission between farms, it seems unrealistic to prevent MAP re-/introductions on farms in the absence of a certification program. The network analysis undertaken in this thesis enhanced the understanding of the role of livestock movement in transmission of MAP. Combined with the simulation model, this work provides options to support farmers’ decision-making and veterinary advice for managing sheep flocks with high OJD mortality.
  • Thumbnail Image
    Item
    A study of circulating neutrophils and exosomes associated with innate immune function in the periparturient grazing dairy cow : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Veterinary Science at Massey University, Manawatū, New Zealand
    (Massey University, 2017) Crookenden, Mallory Ann
    Dairy cows are at greatest risk of infectious and metabolic disease during the periparturient period. This period of three weeks either side of calving is also known as the transition period due to the transition into lactation. This thesis had several aims; one was to characterise innate immune function during the transition period in grazing dairy cows by investigating molecular changes in circulating neutrophils and to assess if common on-farm management strategies (pre-calving feeding level and body condition at calving) were able to influence these molecular changes. Next, metabolic stress on neutrophil function was assessed by establishing a model of cows divergent in metabolic health status. This model was further utilised with the aim to investigate nanoparticles (exosomes), which are regulators of innate immune function and indicators of disease state. To address these aims blood was collected from pasture-fed transition dairy cows. Cellular and molecular methods used included cell and exosome isolation, reverse transcriptase (RT)-quantitative PCR, RNA sequencing, cell culture, and liquid chromatography-tandem mass spectrometry (LC-MS/MS). The results indicated that grazing dairy cows experience a change in innate immune function during the transition period, reflective of reduced functional capacity of the immune system to overcome infectious agents. This altered function was similar to that experienced by housed cows fed a total mixed ration, which adds evidence to support that the dysfunction is a natural part of the transition into lactation at calving. These results also indicated that the functional changes could be influenced by nutrition status, feeding level, and metabolic stress. Analysis of exosomes isolated from the blood of transition cows indicated that these particles carried cargo indicative of metabolic state during the transition period and that they had the ability to alter target cell processes (gene expression, protein expression, and cell proliferation). The conclusions from this thesis increase our understanding of transition cow immune function and how it is influenced by nutrition and cow metabolism. These data are particularly relevant for grazing dairy cows and the findings will contribute to on-farm recommendations and the improvement in animal health and well-being. iii
  • Thumbnail Image
    Item
    Occurrence and distribution of extended spectrum β-lactamase and AmpC-β-lactamase-producing Enterobacteriaceae and methicillin resistant Staphylococcus aureus in companion animals in New Zealand : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Microbiology, Institute of Veterinary, Animal and Biomedical Sciences, Massey University, Palmerston North, New Zealand
    (Massey University, 2017) Karkaba, Ali
    The increasing incidence of infections with extended spectrum-lactamase (ESBL)- and AmpC-producing Enterobacteriaceae, and methicillin-resistant Staphylococcus aureus (MRSA) in humans in the last decade is a matter of concern. There is a paucity of data on the incidence of infections with these bacteria in animals, partly because veterinary diagnostic laboratories do not routinely test for these organisms in clinical specimens. The carriage rate of these bacteria by companion animals is also unknown. This PhD project aimed to investigate the occurrence of ESBL/AmpCproducing Enterobacteriaceae and MRSA in clinical specimens from animals in New Zealand, and examine the carriage of multidrug-resistant (MDR), ESBL/AmpC-E. coli, and MRSA in cats and dogs in Auckland. The results of this project indicate that ESBL/AmpC-producing E. coli and MRSA cause clinical infections in companion animals in New Zealand. The circulation of these bacteria is likely to be posing therapeutic challenges to unaware veterinarians. The bacteria causing infections or carried by companion animals are genetically similar to those found in humans in New Zealand, raising public health concerns about the role of carrier animals as potential sources of zoonotic infections.
  • Thumbnail Image
    Item
    Effect of age on the pharmacokinetics of meloxicam in ISA Brown chickens (Gallus gallus domesticus) : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Physiology at Massey University, Palmerston North, New Zealand
    (Massey University, 2015) Gildersleve, Megan
    The Non-Steroidal Anti-Inflammatory drug (NSAID) meloxicam has been deemed a safe and effective treatment for numerous inflammatory conditions and injuries from extensive pharmacokinetic and pharmacodynamic studies in various mammalian species. However, there is a lack of meloxicam pharmacokinetic information in avian species. This leads to pharmacokinetic data being extrapolated from mammals in order to administer and treat birds. This often leads to ineffective pain relief or overdoses that can be fatal for birds. Due to this void in literature this study was designed to increase the basic pharmacokinetic knowledge in birds but to also determine if age affects the pharmacokinetics of meloxicam in ISA Brown chickens. Meloxicam was injected intravenously (IV) at 2 mg/kg in 20 healthy ISA Brown chickens (Gallus gallus domesticus). One group consisted of 10 ISA brown chickens that were 18 weeks old, the second group consisted of 10 ISA Brown chickens that were 24 months old. Serial blood samples were withdrawn from a catheterised vein from each ISA Brown chicken into a heparinised vial at 0, 10, 20, 30 minutes, 1, 4, 8, 10, 12 hours after the administration of meloxicam. The pharmacokinetics for ISA Brown chickens were calculated using the non-compartmental model, which was analysed using the mean data from each group of ISA Brown chickens. The elimination half-life, steady state volume of distribution and mean resident time were significantly higher in the 24 month old ISB Brown chickens compared to the 18 week old ISA Brown chickens. Overall, the results indicate that as an ISA Brown chicken ages the pharmacokinetics of meloxicam show some significant changes in crucial pharmacokinetic parameters. The differences in the pharmacokinetic parameters may ultimately affect the efficacy of meloxicam when treating ‘geriatric’ birds due to possible age-related health issues in the liver and kidneys, which are major organs involved in processing drugs.
  • Thumbnail Image
    Item
    Efficacy of sustained-release novel bupivacaine formulations in sheep : a thesis presented in partial fulfilment of the requirements for the degree of Master of Veterinary Studies (MVS) Institute of Veterinary, Animal and Biomedical Sciences, Massey University, Palmerston North, New Zealand
    (Massey University, 2017) Sahebjam, Farzin
    The objective of this thesis was to prepare and assess several formulations of the local anaesthetic bupivacaine to achieve a longer duration of action. Intralipid® emulsion (a soybean oil emulsion) and collagen combined with titanium oxide nanoparticles were used to develop slow release bupivacaine formulation. These formulations were tested both in vitro as a pilot study and in vivo in sheep. Collagen was extracted from bovine limed split hide (a by-product of the leather industry). The collagen as a 1% solution was mixed with bupivacaine hydrochloride 0.5% aqueous solution (Marcain® 0.5%, AstraZeneca, New Zealand) giving a final concentration of 0.25% bupivacaine. Intralipid® (20%, Fresenius Kabi Australia) and bupivacaine 0.5% were mixed resulting in a 0.25% bupivacaine lipid emulsion. Both formulations were tested in vitro pilot study for the release of bupivacaine through a dialysis membrane. The concentration of bupivacaine in the dialysate was measured using High-Performance Liquid Chromatography (HPLC). In the animal studies, 18 sheep were used to compare bupivacaine (control) and bupivacaine-Intralipid®, and another 18 sheep for commercial bupivacaine (control) and collagen-bupivacaine. Each sheep received a nerve block using the control or test formulation in each forelimb. The nerve block was placed at the level of the accessory digits with three injections totalling 4 mL using a 22G needle. The efficacy was tested by manually applying a mechanical noxious stimulus with a blunt instrument below the level of the block. This test was performed first after 15 min and then at one-hour intervals. The time at which a response was observed was considered as the end-point for that formulation. In the in vitro pilot study, both collagen and Intralipid®-based formulations showed slightly more sustained release compared to the control group. However, collagen-based formulation of bupivacaine had the most sustained-release among all. In the sheep study, the Intralipid®-based formulation significantly extended the duration of the nerve block compared to the control group (P<0.05). On the contrary, the collagen-based formulation of bupivacaine shortened the duration of action significantly compared to control group (P<0.05). In conclusion, an Intralipid®-based formulation provided a more sustained action after nerve blocks in the sheep metacarpal region compared to aqueous bupivacaine or the collagen based formulation. Further research on structure and activity of collagen and its interactions with bupivacaine is required to develop a longer acting formulation.
  • Thumbnail Image
    Item
    Systemic Mycobacterium avium subspecies paratuberculosis infection in sheep : a thesis presented in the fulfilment of the requirements for the degree of Doctor of Philosophy in Veterinary Science at Massey University, Palmerston North, New Zealand
    (Massey University, 2016) Smith, Stefan Lindsay
    The systemic infection of organs and skeletal muscle outside the alimentary tract with Mycobacterium avium subspecies paratuberculosis (Map) has sparingly been mentioned in the many scientific studies undertaken in sheep, yet within the past decade a zoonotic association has been proposed. The occurrence of systemic Map infection at the time of slaughter might enable this organism to be present in food products, such as meat, destined for human consumption, creating a potential link to public health and may therefore attract some attention by the meat industry. There have been very few studies investigating whether meat has potential to expose humans to Map. With this lack of information, it is difficult for the meat industry to make informed decisions in the event that public perception establishes a link with Crohn’s disease. Chapter one provides a brief history of Map infection in ruminants and suggests there may be a need to identify steps that could be implemented to mitigate human exposure to Map. The aims for this thesis therefore were to i) determine whether skeletal muscle from naturally infected animals provides a source of Map for humans, ii) provide information on systemic Map infection in sheep, identifying classes of stock that may pose a risk for exposure iii) develop a histological diagnostic test for quantifying the cost of systemic Map infection in sheep with potential use in therapeutic efficacy studies, and iv) provide a potential means to mass screen sheep at time of slaughter using real time spectroscopy to identify systemically infected animals. Chapter two reviews the source of Map, transmission pathways and subsequent availability of modern diagnostic tests for identifying sheep infected with this organism. There is a lack of published information on systemic Map infection, with little known about how this event develops, how the immune system reacts when Map bacteraemia occurs, whether systemic Map infection has a cost to production and whether quantification of this cost can be assessed with currently available diagnostic tests. The aim of Chapter three was to determine whether skeletal muscle from ewes with clinical Johne’s disease contained Map and therefore provided a potential source of Map for humans. Fifty one mixed-age, low body condition score ewes (1.5/5), from a farm where clinical Johne’s disease had been diagnosed, were necropsied. This included 48 ewes with Map infection confirmed by ileal BACTEC radiometric culture and 21 with clinical Johne’s disease confirmed by ileal histopathology. In 18 ewes with clinical Johne’s disease, Map was found in the culture of blood (n=13), blood and muscle (n=10) and muscle (n=5). In ewes without clinical Johne’s disease, Map was found in 5/30 animals including muscle (n=4) and blood (n=1). It was concluded that meat from ewes with clinical Johne’s disease is likely to contain Map and suggested that systemic Map infection may also occur in sheep without clinical disease when managed in direct contact with clinically affected ewes shortly before slaughter. The presence of Map within skeletal muscle was further investigated in Chapter four with 24 healthy mixed age ewes selected from one farm, which were not in contact with clinically affected ewes. Ileal and mesenteric lymph node cultures identified Map infection in 12/24 ewes. All other tissues and faeces were culture negative, and only 1/24 animals seroconverted. In flocks where Map is present, it appears that up to 50% of animals may be latently infected. Lack of positive culture from blood and muscle samples in latently infected sheep suggests that meat from healthy sheep may not be a source of human exposure to Map. In New Zealand, the current measure to mitigate human exposure to Map from meat products is the identification of clinically affected sheep prior to slaughter through ante-mortem inspection with emaciated animals rejected at time of slaughter and processed as pet food. However, this screening process is non-specific with many different causes of emaciation. Currently there are no legal requirements or recommendations from the meat industry for the downgrading of meat from carcases with macroscopic signs of clinical Johne’s disease and, as such, meat from these sheep enters the human food chain. Identifying sheep with systemic Map infection is problematic, with diagnosis requiring solid or liquid media culture of Map or polymerase chain reaction (PCR) to identify Map specific DNA. These diagnostic tests are expensive, time consuming and require a high level of expertise. They are therefore unlikely to be adopted by the meat industry as a screening tool for systemic Map infection in sheep. With the aim to develop a diagnostic tool that is relatively quick, simple and cheap, 126 mixed age ewes in poor body condition were euthanised as described in Chapter five and their Johne’s disease status determined through histopathology and Ziehl Neelsen stain of the ileum and mesenteric lymph nodes. Sixty ewes were differentiated histopathologically with 51 clinically affected including Type 3b (n=40) and 3c (n=11) and nine not clinically affected with Type 1 (n=5), Type 2 (n=3) and Type 3a (n=1) ileal lesions. Hepatic epithelioid macrophage micro-granulomas (HEM) were observed only in ewes with Type 3b or 3c ileal lesions, all of which were ELISA positive. When present, HEM were in equal densities in liver section and biopsy samples. The sensitivity and specificity for liver histopathology (section or biopsy) for predicting clinical OJD was 96% (95% CI, 87-99%) and 100% (95% CI, 95-100%), respectively, and Cohen’s Kappa had an almost perfect level of agreement between HEM formation, ileal pathology and ELISA sero-positivity. This study determined that the presence of HEM provided a surrogate measure of ileal pathology, identified ewes with clinical Johne’s disease, and that biopsy samples and post mortem sections were equally suitable for the diagnosis of HEM. Encouraged by the predictive quality of HEM in Chapter five, it was hypothesised that the identification of HEM from biopsies may provide a method to follow the progression of Map infection through serial sampling and to quantify the production cost of systemic Map infection. The longitudinal challenge study in Chapter six utilised the identification of HEM as an indicator of systemic Map infection in naïve lambs orally challenged with 1 x 109 organisms on ten occasions over 30 days. The presence of HEM was related to live weight gain, body condition score, development of clinical disease or occurrence of self-cure (recovery), and ELISA serology All challenged lambs developed HEM, a higher density of HEM was associated with increased ELISA S/P ratios with a Cohen’s kappa substantial level of agreement, and mean weight loss (-2.03kg) from 51 to 154 days post challenge with an almost perfect level of agreement. Thereafter, lower weight gain led to a mean body weight difference of -8kg at 195days compared to non-challenged lambs. Four challenged lambs had to be euthanised due to clinical OJD. After this period, the HEM density and ELISA S/P ratios declined, growth rates increased in the challenged lambs up to 482 days after which no HEM were detected and growth rates were equal between challenged and unchallenged groups. The challenged lambs failed to regain equivalent weights over the 820 days being 11kg lighter at the end of the study despite having equal body condition scores. The challenged lambs were smaller than the unchallenged lambs both in body height and length with multivariate ANOVA analysis determining the post mortem mean skeletal measurements of the poll to rump length and metacarpal/meta-tarsal bones being 4% and 5% shorter, respectively. There were no positive ELISA blood samples or histopathological lesions in any tissues sampled at necropsy from both groups of lambs at the end of the study, suggesting complete cure of the surviving challenged lambs. The findings demonstrated i) that artificial challenge can cause systemic Map infection, ii) systemic infection results in negative growth rates and a loss of body condition, iii) and in addition to the period of retarded growth losses occur from death of some lambs (4/18), iv) that the temporary poor weight gain impacted on the final weight, and v) that recovery to systemic Map infection appears to occur in survivors of acute disease. Moreover, it was postulated that the identification of HEM from serial liver biopsies may have the potential to determine the therapeutic efficacy of new anti-mycobacterial drugs (such as thalidomide, Appendix one) or vaccines for preventing systemic Map infection. Chapter seven revisits the histopathological findings described in Chapter five, expanding from the microscopic visual identification of HEM to utilising spectroscopy and hyperspectral image analysis. The aims of this final study included identifying whether a spectral signature for skeletal muscle or liver exists in sheep with Johne’s disease and developing an algorithm that can identify the presence of systemic Map infection in sheep. Ninety five mixed aged ewes, of low body condition score from nine farms were euthanised and OJD was confirmed by histopathology in 10 animals. The liver and transected longissimus dorsi muscle were scanned using a visible light to near infrared (Vis-NIR) detector as well as 200 lamb livers from a slaughter house. The histological identification of HEM was used as a surrogate measure of systemic Map infection with HEM recorded in the 10 ewes with Johne’s disease and none of the 85 ewes without or the 200 lamb livers. There was no histopathological or hyperspectral differences identified for the transected longissimus dorsi muscle in the 95 ewes. However a a computer generated algorithm identified a hyperspectral signature for liver tissue that when applied, blind to the Johne’s disease status of the ewes was able to differentiate all 10 animals with Johne’s disease from the 85 ewes and 200 lambs without. This pilot study suggests that spectroscopy may have potential to be a useful real time tool for the identification of sheep with systemic Map infection at the time of slaughter. In conclusion, disseminated Map infection does occur in sheep with clinical OJD, and meat from these animals can be a source of Map for humans. Meat from healthy sheep or sheep without clinical OJD does not appear to expose consumers to Map. The identification of HEM in liver biopsies has diagnostic value for identifying sheep with clinical OJD. In naturally infected sheep, HEM only appear when Map infection has progressed to clinical OJD. As opposed to high–dose artificial challenge, systemic Map infection under natural challenge conditions appears to require ileal pathology, suggesting different mechanisms for the occurrence of systemic infection in these two challenge types. Examination of serial liver biopsies and the identification of HEM has enabled the investigation of the production loss due to temporary progression and subsequent resolution of Map infection. The final study in this thesis has tested proof of concept for a new real time diagnostic test that has potential to mass screen sheep within abattoirs at point of slaughter using spectroscopy and hyperspectral analysis. However further research is required to validate this spectroscopic test.
  • Thumbnail Image
    Item
    Racing to retirement : understanding greyhounds' experiences of becoming pets : a dissertation presented in partial fulfilment of the requirements for the degree of Masters of Arts in Social Anthropology at Massey University, Manawatū, New Zealand
    (Massey University, 2017) Paap, Hannah
    This thesis is a multispecies ethnographic investigation of the transition of retired racing greyhounds to domestic pets. The key aim of this research was to understand the greyhounds’ experiences of this transition. To achieve this aim, I sought to understand the relationships that greyhounds have with both human and non-human animals over the course of their transition and how these relationships influenced the pets they became. I use the concept of rite of passage to frame greyhounds’ transition because they move from one societal role, working dogs, to another, pets, undergoing transformation in the process. My fieldwork involved a mixed methodological approach, combining participant-observation, interviews, and photography. In doing so, I gained insight into greyhounds’ own experiences of their rite of passage and not just that of the humans involved in their lives. To help me do this, I combined ethnography with ethology, the science of animal behaviour. Using ethology allowed me to learn how greyhounds used their senses to investigate and make sense of the changes in their lives, which were brought about by their transition, and how they responded to and communicated about them. I did this by interpreting their body language, body carriage, and vocalisations. Thus, greyhounds play a central role in this thesis, whilst the human is decentred. The goal of this research was to centre greyhounds, even though it is challenging to do this in text: as such this thesis is an experiment in representation. My findings suggest that greyhounds can successfully transition into pets due to breed-specific traits, such as laziness; individual dog personalities like independence; and the constructive interactions they have with both human and non-human actors. This is even though some greyhounds may find their rite of passage more difficult than others. Keywords: greyhound(s). racing dog, transition, retirement, adoption agency, (domestic) pet, multispecies ethnography, rite of passage, non-human animal, human companion, companion animal, companion species.
  • Thumbnail Image
    Item
    Lead exposure in an urban population of free-ranging kaka (Nestor meridionalis septentrionalis) : a thesis presented in partial fulfilment of the requirements for the degree of Master of Veterinary Science in Wildlife Health at Massey University, Palmerston North, Manawatu, New Zealand
    (Massey University, 2017) Sriram, Aditi
    Anthropogenic lead use has resulted in widespread environmental lead contamination known to affect wildlife populations worldwide. Lead is a highly toxic, non-essential heavy metal recognised as a cause of morbidity and mortality in birds. Ecotoxicological investigations in wild birds have thus far prioritised waterfowl and raptor species and primarily addressed contamination in natural ecosystems. Urban areas are increasingly associated with high levels of heavy metal contamination, however the risk of lead exposure in urban wildlife is less well known. This study aimed to identify the significance of lead exposure in a well-established urban population of kaka (Nestor meridionalis septentrionalis). Blood lead concentrations were assessed in adult and nestling birds to quantify exposure prevalence and magnitude. The impact of lead exposure on physiological and neurological function was assessed using behavioural and physiological parameters. Finally, lead stable isotope analysis was employed to identify the primary sources of lead in the urban environment. Lead exposure is prevalent in this kaka population, with 43.2% of adults and 36.7% of nestlings with detectable blood lead concentrations. Blood lead concentrations in nestlings ranged from <3.3 to 42.9ug/dL, with no detectable neurological or physiological deficits. The pattern of exposure in chicks is suggestive of parental feeding of lead, however detection of lead in some eggshells suggests that maternal transfer is another route of exposure in this species. Blood lead concentrations in adult birds ranged between 3.4 to 50.7ug/dL. Although no acute clinical signs of toxicity were observed, lead exposure was associated with reduced body condition in adults. Behavioural changes were present in one individual with the highest recorded blood lead concentration. Lead isotope ratios in kaka blood samples overlap with isotope values of roof-collected rainwater, suggesting this to be an important source of exposure in this population. The prevalence of lead exposure observed in this study suggests that lead is a threat to kaka interacting with urban areas. Wildlife intoxications largely result from anthropogenic lead sources and this study identifies a previously undescribed urban source of lead in wildlife. The well-described subclinical and persistent effects of lead highlight the need for abatement strategies to reduce lead exposure and its effects in this population.
  • Thumbnail Image
    Item
    Estimation of gestational age by the use of fetal parameters : placentome, femur length, and biparietal diameter : a dissertation presented in partial fulfillment of the requirements for the degree of Master of Veterinary Studies at Massey University, Institute of Veterinary, Animal and Biomedical Sciences, Massey University, Palmerston North, New Zealand
    (Massey University, 2015) Bunyaga, Aloyce Shukran
    The research was conducted at (LATU) Large Animal Teaching Unit, Massey University, New Zealand. The study involved 23 beef cows and 60 dairy cows. The aim of the study was to test and assess the agreement between actual gestational age and that predicted using a model developed in previous studies based on placentome length (gestational age = placentome*2.88 - 6.11; Adeyinka et al., (2014) and to compare this agreement with that obtained using fetal measurements of femur length and head size (biparietal diameter). The research commenced on February 2015 and July 2015 for beef and dairy cows respectively and ended June 2015 and September 2015 for beef and dairy cows respectively. Beef cows were scanned transrectally every after three (3) weeks while dairy cows were scanned every after one (1) week.. Overall there was no evidence of bias in all the parameters studied. The strongest association (R2=0.85) was seen in dairy cattle when biparietal diameter was measured and the weakest was placentome size in dairy cattle (R2=0.39). This is the first study that has specifically focused on the agreement between estimates of gestational age from fetal size and actual gestational age. This study has shown biparietal diameter to be a better predictor of gestational age than mean placentome size across the range of gestational ages found in this study. However, because the limits-of-agreement for biparietal diameter increase as gestational age increases, by 120 days of gestation the difference between the limits-of-agreement for biparietal diameter and those for mean placentome size are much smaller than in early gestation, and the limits-of-agreement for biparietal diameter are similar to those previously reported where data from all placentomes measured were used to predict gestational age rather than just a single mean placentome size. At 120 days of gestation, placentomes can be measured in a much higher proportion of cattle than biparietal diameter, and even when the latter can be measured, placentome measurements are markedly easier to obtain. Femur length was by far the most difficult parameter to measure and especially by 120 days was much less precise than mean placentome size or biparietal diameter. Therefore, femur length should be restricted to use only in early gestation and then should be used alongside other parameters like biparietal diameter.
  • Thumbnail Image
    Item
    The effect of dietary cadmium on kidney function in cats : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Animal Science at Massey University, Palmerston North, New Zealand
    (Massey University, 2017) Anderson, Jeanette M J
    Due to the requirement for meat in feline diets, this study aimed to investigate the potential effects on kidney function in cats of cadmium accumulation in meat products due to pasture management practices. Cadmium may be a causal factor in feline Chronic Kidney Disease (CKD). Twenty-seven domestic short hair cats were randomly selected from the colony population of the Feline Nutrition Unit of Massey University and assigned to three experimental groups (n=9), which were balanced for age and sex. Each group received one of the three experimental diets designed to represent the full range of potential cadmium concentrations that cats may be exposed to on wet diets in New Zealand. Diets were fed ad libitum for a 6-month period. Kidney function was examined at baseline and after 3 and 6 months by measuring glomerular filtration rate (GFR) using iohexol clearance analysed by high performance liquid chromatography (HPLC). Blood and urine analyses were also conducted on a monthly basis. While GFR fluctuated over the study period no significant differences were found either between groups at the end, or within each group when compared at the beginning and end of the study. Although overall no evidence of CKD was observed, an unexplained trend of weight loss was observed in females receiving the two diets containing the highest cadmium levels, which may simply have reflected reduced dietary palatability. The results of the study showed no detectable effects of feeding the three diets for 6 months; however, an extended trial period may be required to fully investigate the longer term effects of cadmium levels and other dietary factors on the development of CKD. In particular, more work is needed to explore the potential for genetic and/or functional differences in mechanisms which are involved in the transport, and/or deposition of cadmium, or are protective against cadmium toxicity in cats and to further define normal parameters and standard approaches in measuring GFR in cats.