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    Effect of dietary processing on the gut microbiome of dogs (Canis lupus familiaris) : 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, 2024) Tannahill, Lucy May
    The gastrointestinal microbiome of the dog plays important roles in the overall health of the dog. Generally, a greater microbiome diversity is indicative of better gastrointestinal health. The microflora in the gastrointestinal tract can be altered by the diet that the dog is consuming. Therefore, it is important to understand how the diet interacts with the dog’s microbiome, to further expand our knowledge of the overall health of dogs. This study investigated the effects of processing of a series of high meat diets on the gastrointestinal microbiome of dogs. A literature review was carried out to establish the current base of knowledge of the microbiome of the dog, and how the diet may affect it. The nutritional requirements of dogs, as well as how diets are assessed for suitability were also reviewed. To assess the impact of diet changes on the microbiome, a series of standard digestibility trials were run. To do this, a raw version, and a processed version of two diets were fed to a group of dogs over two-week blocks, as well as two high meat kibble diets in subsequent blocks. The faeces were collected over a period of five days, with a final faecal sample taken on the final day. This enabled a digestibility analysis to be completed, and the microbiome to be analysed using 16S sequencing which allowed comparisons to be made between the microbiota present in the gut while the dogs were consuming a raw and processed version of two of the diets and two other high meat diets. A high number of reads were present in all samples after the 16S sequencing was completed, and Bacteroidetes, Firmicutes, Fusobacteria and Proteobacteria were the phyla present in the largest proportions on average across all the samples. Phascolarctobacterium, Prevotella, Bacteroides and Fusobacterium were the most prominent genera. The diet with the highest microbial diversity was Blackhawk (BH) and the diets with the least were steamed and dried raw (SDR) and Orijen (OR). The two unprocessed diets had lower diversity present in the gut microbiome than their processed counterparts. This suggests that the processing those diets went through did result in positive changes in the microbiota compared to the raw versions. Microbiomes that are more diverse are generally thought of to be healthier than ones with less diversity present.
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    The effect of inorganic dietary phosphorus on the digestibility of the diet and renal health of the domestic feline (Felis catus) : 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, 2024) Manville, Taylor Rhonda
    With the increasing prevalence of feline chronic kidney disease (CKD), there is a growing focus on dietary intervention to reduce the incidence and slow the progression of this disease in domestic cats. Studies investigating the effects of feeding high phosphate levels have been of particular interest, as this has been closely associated with reduced renal function in healthy cats and dogs. Phosphate additive supplementation is common practice in pet foods to improve texture or palatability, and the nutritional guidelines for cats only regulate a minimum P requirement. Given the adverse effects of excessively high dietary P on the renal function of various species (e.g., cats, dogs, and humans), there is clear need for a determined maximum or “safe upper limit” of P intake to be implemented for feline health. There is also a need to determine how different P sources (inorganic vs organic) affect animal health, as high concentrations of the more bioavailable inorganic P (Pi) have been shown to be particularly problematic for renal health. This study aimed to investigate the effects of feeding diets with differing P sources on indicators of feline renal health. Eight healthy young and desexed domestic shorthair cats (four males and four females) from the Centre of Feline Nutrition (Massey University, Palmerston North, New Zealand) were used for this study. The cats were aged 1-4 years (mean ± SEM: 3.05 ± 0.10 years) and weighed 2.4-5.6 kg (mean ± SEM: 4.26 ± 0.24 kg). All cats were sequentially fed three dietary treatments: control diet (CON; diet containing 3.75 g organic P/kg), test diet 1 (T1; diet containing 3.75 g organic P/kg and 2.39 g Pi/kg), and test diet 2 (T2; diet containing 3.75 g organic P/kg and 3.25 g Pi/kg), all in the form of canned moist food. Each diet was considered complete and balanced according to the AAFCO guidelines and was formulated to have different Ca:P ratios (CON: 1.6:1; T1: 0.9:1; T2: 0.6:1) in order to determine whether the Ca:P ratio affected P digestibility. Each diet was fed for 26 days, beginning with a 7-day adaption phase, and ending with a 6-day apparent nutrient digestibility assessment. The cats had ad libitum access to the food and water, which were both replaced daily, throughout the study. The total P and Pi/Mcal differed in each test diet (Total P: T1: 6.19 g/kg DM, T2: 7.65 g/kg DM; Pi/Mcal: T1: 0.53 g/mcal, T2: 0.68 g/mcal). Blood sampling took place on day 26 of each feeding block, and included a preprandial/fasted sample (12 h minimum) and two postprandial samples (3 h and 5 h after food intake). Quantitative collection of faeces and urine took place during the six-day apparent nutrient digestibility period at the end of each diet block. The effects of dietary Pi supply on calcium (Ca) and P balance were assessed through blood, faecal and urine analyses, and changes in renal markers (i.e., creatinine, symmetric dimethylarginine, fibroblast growth factor-23 (FGF23), parathyroid hormone (PTH) and specific gravity) were investigated to determine the implications of feeding Pi on the feline kidney. Based on blood analyses and frequent weighing and monitoring, all eight cats remained clinically healthy for the duration of the study. The average body weights of the cats decreased throughout both the CON and T1 blocks, but increased gradually during the feeding of T2. These body weight changes were likely at least partly due to normal seasonal body weight changes. There was a significant increase in P intake in the T1 and T2 trial diets compared to the CON diet. The higher level of NaH₂PO₄ and Pi/Mcal in diet T2 led to the greatest P intake (mg/kg BW) and apparently digested P (mg/kg BW). The CON trial provided the baseline assessment of renal function. The addition of Pi in both trial diets (T1 and T2) caused an unexpected drop in serum concentrations of P and corresponding levels of FGF23. Despite the low serum P concentrations observed, there was a significant increase in both PTH concentrations and renal P excretion. In addition to this, urine analyses indicated that specific gravity and pH levels were lowest during the T2 trial. This study indicated that when Pi was added to the feline diet in moderate amounts, there were significant changes in phosphate metabolism. Additionally, the diet containing a Ca:P ratio lower than the reference range and a higher level of NaH₂PO₄ and Pi/Mcal (T2) induced a greater renal response, especially the renal excretion of P. This suggests that the potential for renal damage may be increased if the dietary Pi had been added in greater quantities. The evident effects of including moderate levels of highly soluble Pi and a low Ca:P ratio in the feline diet emphasises the need for further investigations into feeding these Pi sources for longer periods and potentially assessing further parameters of renal health.
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    Population ecology and foraging behaviour of yellow-eyed penguins in New Zealand’s subantarctic Auckland Islands : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Veterinary Science and Ecology, Massey University, Manawatū, New Zealand
    (Massey University, 2022) Muller, Christopher
    Penguins and other seabirds rely on healthy, functioning marine systems, and are vulnerable to human-induced changes. Accurate long-term monitoring of a threatened species’ population size and trend is therefore important for conservation management. The endangered yellow-eyed penguin (Megadyptes antipodes) is found only in New Zealand waters, with separate northern (mainland New Zealand and offshore islands) and southern (subantarctic) breeding populations. The northern population is declining, believed to be due to threats at sea including direct mortality, as well as changes to food supply, and the effects of climate change. The southern population was previously estimated to comprise at least 60% of the species. Despite this, the subantarctic has been little studied, with one previous population estimate at the Auckland Islands in 1989, two at Campbell Island, and no recent data or measurement of population trends. To address this data gap, this research studied the population and foraging behaviour (diving, foraging location, and diet) of breeding yellow-eyed penguins on Enderby Island, Auckland Islands, from 2015–2017. The first step for this research was locating cryptic yellow-eyed penguin nests hidden in thick vegetation, as ground searches are inefficient, time-consuming, and potentially hazardous for researchers in subantarctic terrain. I utilised a drone fitted with a novel multi-frequency VHF receiver which located nests in only 3% of the time for traditional search methods, facilitating my other research. Next, I defined methods for surveying populations in the subantarctic, and estimated a mean of 577 breeding pairs at the Auckland Islands, although the population and number of breeders fluctuated annually, and may have declined since 1989. My foraging research showed that 62% of foraging trips, and over 86% of all southern yellow-eyed penguin dives were pelagic (mid-water), unlike the predominantly benthic (seabed) dives of the northern population. Maximum dive depth was 134 m for benthic dives, and 115 m for pelagic dives, which is deeper than many northern penguins dive. The proportion of pelagic dives increased during La Niña years, likely influenced by climate conditions and prey availability. Foraging distance also varied, with a maximum distance of 47 km from shore, further than many northern birds travel. Foraging area size was greater for females and for pelagic foragers, although benthic foragers travelled further from shore on average. Diet also varied, and during El Niño conditions comprised lower trophic level prey, which were more benthic, and found closer to shore than during La Niña years. Diet results showed some individuals maintained consistent foraging behaviour, although foraging plasticity was also evident. Some individuals changed their foraging behaviour between years, and even within a breeding season. Variable breeding success in the subantarctic, along with variable foraging behaviour and diet suggests that prey availability is likely limiting the southern population in some years. Prey availability is therefore expected to be a major influence on survival and breeding success in the future, particularly if the effects of climate change become more pronounced.
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    Behaviour and diet of the Tasman parakeet (Cyanoramphus cookii) on Norfolk Island, South Pacific : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Conservation Biology, Massey University, Albany, New Zealand
    (Massey University, 2020) Brett, Georgia Michelle
    Conservation of threatened species requires an understanding of their biology in the wild, including aspects of their dietary diversity, general behaviours and interactions with other species. For many threatened species however, obtaining even basic information about their biology in the wild proves challenging. This is because they often occur in small numbers, or in remote locations, limiting our ability to quantitatively describe behaviours. The Tasman parakeet (Cyanoramphus cookii) endemic to Norfolk Island, has experienced two cycles of critically low numbers in the last 40 years. Since the 1970s, the species is the subject of regular management, chiefly including introduced predator control and the provisioning and maintenance of predator-proof nests within the Norfolk Island National Park. These actions have resulted in population increases to approximately 400 individuals by 2018. As Tasman parakeets numbers increase, managers face challenges to target interventions that could help Tasman parakeets establish and reproduce as they disperses outside the National Park. In this thesis I examine the behaviour of Tasman parakeets and crimson rosellas (Platycercus elegans) during winter and spring to understand the response of both species to disturbance (presence of observers). I also examined the diversity of food species consumed by Tasman parakeets and crimson rosellas within and outside the boundaries of the National Park. During this research, Tasman parakeets were first sighted at shorter distances than crimson rosellas, furthermore, Tasman parakeets were observed at lower heights than crimson rosellas. Overall, these findings reinforce that Tasman parakeets are behaviourally more vulnerable to introduced predators than crimson rosellas, with further research required. I also determined that Tasman parakeets and crimson rosellas overlap in feeding resources and both species rely heavily on seeds of Norfolk pine (Araucaria heterophylla) during winter, however further examination of seed availability and potential competition is required.