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    The use of breath hydrogen testing to evaluate carbohydrate malabsorption in dogs : a thesis presented in partial fulfilment of the requirements for the degree of Master of Veterinary Science in Small Animal Medicine at Massey University
    (Massey University, 1997) Bissett, Sally Ann
    The use of the breath hydrogen test in this thesis has focussed primarily on the study of carbohydrate assimilation in healthy dogs and in dogs with gastrointestinal disease. The gastrointestinal handling of dietary carbohydrates and the rationale, applications, and limitations of the breath hydrogen test have been reviewed. Studies were undertaken to investigate the effect of food particle size on carbohydrate digestion and the effect of dehydration on breath hydrogen concentrations in healthy dogs. In addition, breath hydrogen testing was used to assess the assimilation of four commonly used commercial carbohydrate sources in dogs with gastrointestinal disease. In each study, expired breath samples were collected at regular intervals after the ingestion of a carbohydrate test meal. The excretion of hydrogen in the breath was compared between groups, mainly by analysis of the areas under the breath hydrogen concentration versus time curves. The reduction of food particle size was found to cause starch granule disruption and significantly decreased the amount of malassimilated rice. The assimilation of corn, however, did not appear to be altered by reducing the food particle size. Instead, an earlier rise of breath hydrogen concentrations occurred, indicating more rapid orocolic transit and/or fermentability of the smaller corn particles. Five percent dehydration, induced by food and water deprivation, was found to significantly elevate breath hydrogen concentrations and was associated with a significantly greater number of flatus-contaminated breath samples. This increased breath hydrogen excretion associated with increased flatulence in dehydrated dogs was attributed to a greater "net" production of hydrogen within the gastrointestinal tract. Finally, breath hydrogen concentrations were not found to vary significantly between four different extrusion cooked carbohydrate sources (wheat, potato, corn, rice). However, it could not be concluded that these carbohydrates were assimilated to a similar extent as in vitro fermentation results revealed marked differences in the amount of hydrogen produced per gram of carbohydrate fermented at different fermentation times. Individual dogs with gastrointestinal disease appeared to differ in their ability to assimilate the four different carbohydrate sources. In addition, dogs with exocrine pancreatic insufficiency were found to malabsorb significantly more carbohydrate than the dogs with mild inflammatory bowel disease. In conclusion, food processing to reduce carbohydrate particle size appears to increase the assimilation of rice. Methods to reduce the particle size of rice should be considered in the formulation of veterinary therapeutic diets for the management of diarrhoea. Mild dehydration appears to increase breath hydrogen excretion. This suggests that breath hydrogen tests should not be performed on animals that are suboptimally hydrated until their hydration deficits have been restored. The marked individual variation of carbohydrate assimilation noted in dogs with gastrointestinal disease, suggests that clinicians should consider altering the carbohydrate source offered to dogs with intractable malassimilation. with the aim of finding the carbohydrate best tolerated. Finally, direct comparison of breath hydrogen concentrations should not be used to compare the digestibility of different complex carbohydrates unless an accurate means is available of comparing the amount of hydrogen produced per gram of substrate fermented in vivo.
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    Research into causes of diarrhoea associated with the Hill's prescription diet Canine Z/D® Ultra Allergen Free : 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, 2003) Hekman, Margreet
    The history, manufacture, physical and immunological characteristics, nutritional adequacy, formulation, taste and digestibility of protein hydrolysates were reviewed. Studies were then undertaken to investigate the cause of the diarrhoea reported to occur in dogs fed an early formulation of Hill's Prescription Diet Canine z/d® ULTRA Allergen Free. It was hypothesised that the digestibility of Canine z/d® ULTRA Allergen Free was poor and therefore contributing to the diarrhoea. To test this hypothesis a study was designed to assess the apparent ileal digestibility of the Canine z/d® ULTRA Allergen Free diet using a rat model of apparent ileal digestibility. The results of this study showed the apparent ileal digestibility of the Canine z/d® ULTRA Allergen Free diet was high and it was concluded that the digestibility of the diet does not predispose dogs to diarrhoea. The reported high osmolarity of protein hydrolysate diets was considered a potential contributing cause to the diarrhoea. To test this hypothesis, the osmolarity of the Canine z/d® ULTRA Allergen Free diet was compared to a standard maintenance diet and to a diet formulated for the treatment of diarrhoea. The osmolarity of the Canine z/d® ULTRA Allergen Free diet was approximately twice that of the osmolarities of the other two diets. This difference was statistically significant (p<0.05), and the data from this study suggest that the hydrolysate diet was sufficiently hyperosmolar to be capable of damaging the mucosa. Although of interest, these observations do not, however, allow a conclusion that the reported diarrhoea is due to hyperosmolarity. Lastly, breath hydrogen tests were performed to investigate whether carbohydrate malabsorption, abnormal orocolic transit times or small intestinal bacterial overgrowth played a role in the cause of the reported diarrhoea. The breath hydrogen concentrations of dogs fed the hydrolysate diet remained within reference intervals confirming the high carbohydrate digestibility observed in the rat model of apparent ileal digestibility and providing no support for abnormal orocolic transit or bacterial overgrowth of the small intestine as causes for the reported diarrhoea. In conclusion, the results of the studies in this thesis do not provide a clear explanation for the cause of the diarrhoea reported to occur with the Canine z/d® ULTRA Allergen Free diet.
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    Hindgut digestibility in the dog (Canis 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, 2006) Singh, Ishwani
    Digestibility trials are important tools used by nutritionists to establish the nutrient requirements of an animal. The most common method used is total faecal collection, which involves the total collection of faeces over a limited period of time. Digestibility trials can also use indigestible markers, such as chromium oxide and titanium oxide, which eliminate the need for a total faecal collection and instead uses sub-sampling methods. The major aim of this thesis was to compare the suitability of chromium oxide (Cr₂0₃) and titanium dioxide (Ti0₂) as indigestible markers in dogs. Due to constraints in the study design (limited space in the facility and therefore a requirement to house dogs in pairs), it needed to be established if Ti0₂ interfered with the chemical analysis of Cr₂0₃ before any animal trials were undertaken. Different concentrations of both markers were added to freeze dried dog faeces. The indigestible markers were then analysed for in the laboratory and recoveries calculated. lt was established that there was no interference of the analysis by either marker. After a pilot study confirmed that coprophagy did not occur in the dogs, the first study (Chapter 2) used 12 entire female Harrier hounds housed in pairs in 6 concrete floor pens. The dogs were fed twice daily with one of 4 treatment diets; a high nutrient diet containing Cr₂0₃ or Ti0₂ or a low nutrient diet containing Cr₂0₃ or Ti0₂. Daily intake was recorded for each dog. Each dog received each of the 4 diets over 4 consecutive evaluation periods of 14 days each. This study showed that 100% recovery of markers was not achieved in the dogs. Recoveries of Cr₂0₃ were 58% and 76% respectively for high and low nutrient diets, and recoveries of Ti0₂ were 80% and 74% respectively for the same two diets. These results suggest that Ti0₂ is currently the best indigestible marker for use in dogs. Study 2 (Chapter 3) used 5 adult female Beagle dogs with surgically prepared ileal cannulas. The ileal cannulation was conducted according to the method of Walker et al. (1994), and the dogs were housed individually in floor pens in temperature controlled rooms. The dogs were fed 5 commercial AAFCO approved diets with free access to water. Dogs were randomised in a replicated 5x 5 Latin-square design with 14 day periods, consisting of a 10 day adaptation period and a 4 day ileal and faecal collection period. lt was found that there were significant differences between ileal and faecal digestibility of dry matter, crude protein, organic matter and carbohydrates of the nutrients that we tested, indicating that there was significant metabolism of nutrients in the hindgut of the dog.