Factors influencing vitamin B6 status in domestic cats: age, disease, and body condition score

Limited studies are available on vitamin B6 status in domestic cats. To this end, we evaluated glutamate-oxaloacetate transaminase (GOT) activity in hemolysates with and without pyridoxal 5'-phosphate addition in two feline populations: a cohort of 60 healthy, domestic (sexually intact and specific pathogen-free) cats maintained under strictly controlled conditions with appropriate diets housed at the Feline Nutrition and Pet Care Center, and a cohort of 57 cats randomly selected between December 2022 to January 2023 that visited the Veterinary Medicine Teaching Hospital to seek care under different circumstances. The GOT activity expressed as the ratio with and without pyridoxal 5'-phosphate addition (primary activation ratio; PAR) decreased significantly with age in the healthy cohort. The PAR values normalized to age established a cut-off for vitamin B6 deficiency in both cohorts, identifying 17 of 101 animals as vitamin B6 deficient. Using machine learning, a partition-based model (decision tree) was built to identify the most important factors that predicted vitamin B6 deficiency while using the resulting tree to make predictions for new observations. This analysis, performed with all 101 cats, revealed that the diagnosis of an infectious, chronic or acute condition (0.55) was the main contributor, followed by age (0.26), and body condition score (optimal-overweight; 0.19). Thus, our study supports that vitamin B6 supplementation may be indicated in junior to adult animals diagnosed with an infectious, chronic, or acute conditions or healthy cats with body weight ranging from optimal to overweight. In older cats, even if healthy, underweight to optimal cats appear to be at risk of vitamin B6 deficiency.

Reproduction of Domestic Cats in Laboratories, Catteries, and Feral Colonies: A Review

Cat reproduction is important for research and commercial cat breeding operations, as well as the control of feral cat populations. This review describes studies examining reproductive performance in laboratory cats, privately-owned breeding cats, and feral cats, including sexual maturity, the estrous cycle (timing, behavior, and hormonal changes), seasonal effects, gestation length, parturition (litter size, litter weight, and parity effects), mortality, and stillbirth. Because the studies highlighted in this review vary in the location where they were conducted and the region's management practices, these factors should be considered depending on the goal of the reader when interpreting these data. Furthermore, standard practices were lacking in some earlier studies of cat reproduction, so they should be considered for historical context only and may not reflect the actual reproductive potential of cats as described in the new studies due to advancements in husbandry practices and nutrition. The objective of this manuscript is to review scientific studies examining reproductive performance in laboratory cats, privately-owned breeding cats, and feral cats. The data sources for this manuscript included original research publications and scientific reviews from the veterinary literature. All reviews or studies that augmented the knowledge of the reproduction of domestic cats in laboratories, catteries, and feral colonies were included. Most studies on laboratory cats have been conducted under the conditions of controlled light cycles, temperature, and diet. The environmental effects on reproductive behavior are subtler than those in feral cat studies, but the effects are still distinguishable. Cat breeding studies focus on genetic effects and rely heavily on surveys or questionnaires from cat breeders. However, the reliability of these data can be variable, in part because the methodology of record-keeping and other protocols are generally not reported. In addition, laboratory animal management standards, specific pathogen-free cat colonies, and nutritional requirements for cats were not fully established until the 1970s. Reproductive outcomes of earlier studies may not be a true representation of the modern cat due to more advanced, regulated husbandry practices, including improvements in nutrition, resulting in diets formulated to meet feline requirements for every life stage.

Impact of blood tube additives and timing of sampling on blood taurine concentrations in clinically healthy dogs

INTRODUCTION

Dilated cardiomyopathy can be associated with taurine deficiency in dogs. Blood taurine concentrations can be analyzed in whole blood (WB) and plasma. The study objectives were to investigate agreement between taurine concentrations measured in WB, heparin plasma, and EDTA plasma, determine intraindividual variation in healthy dogs, and evaluate if time from feeding to sampling impacts concentrations.

ANIMALS

Ten English Cocker spaniels and 10 dogs of various breeds.

MATERIALS AND METHODS

Dogs were fasted 12 h prior to initial blood sampling, and the blood was collected at five occasions over eight h. Food was offered immediately after first and one h after fourth sampling time point.

RESULTS

Agreement between taurine concentrations in EDTA plasma and heparinized plasma was good (mean difference 4.5 nmol/mL, 95% confidence interval (CI) 36.8-45.8 nmol/mL). Whole blood concentrations were systematically higher than EDTA and heparin plasma concentrations (mean difference 132.7 nmol/mL, 95% CI 23.6-241.8 nmol/mL, and 127.6 nmol/mL, 95% CI 28.6-226.6 nmol/mL, respectively, all P < 0.001). Intraindividual daily variations in taurine concentration were seen in all additives, with largest variations in plasma (P < 0.001). Taurine concentration in heparinized plasma was higher at first and fifth sampling time points compared to the fourth (P = 0.014).

DISCUSSION

Agreement was found between taurine concentrations measured in different additives, with expected higher concentration in WB than plasma. Taurine concentrations measured in heparinized plasma varied with sampling time point. Intraindividual daily variations were observed in all additives, but mainly in plasma samples.

CONCLUSION

Taurine concentrations in dogs with suspected deficiency should be interpreted with caution.

Determination of Mammalian Deoxyribonucleic Acid in Commercial Canine Treats and Supplements

Feeding an elimination diet exclusively is currently the only accurate diagnostic test for an adverse food reaction in dogs and cats. However, owner compliance has been identified as a challenge, and the inability to limit exposure to other items (including treats and supplements) is a remarkable reason for failure. The objective of the current study was to evaluate the presence of declared and undeclared mammalian deoxyribonucleic acid (DNA) in commercially available canine treats and supplements using polymerase chain reaction methodology. Eight treat products and 20 supplement products were analyzed for the DNA of 10 mammalian species (bison, cat, cow, dog, goat, horse, mouse, rat, pig, and sheep). The results showed that 88% (7/8) of treats and 40% (8/20) of supplements were found to contain at least one source of undeclared mammalian DNA. Undeclared pig and cow DNA were the most frequently identified, and there were only two instances of negative results for declared species. Because of the frequent finding of undeclared mammalian DNA in the assessed products, avoiding using treats and supplements during elimination trials is recommended.

Prevalence, risk factors, and disease associations of overweight and obesity in cats that visited the Veterinary Medical Teaching Hospital at the University of California, Davis from January 2006 to December 2015

Overweight and obesity are commonly diagnosed in domestic cats, and undermine cats' quality of life directly or indirectly via various disease processes known to be associated with overweight and obesity. Epidemiological studies have reported varied overall prevalence among different feline populations, and commonly identified risk factors such as neutering. However, disease associations were not consistently reported. The status of feline overweight and obesity in a referral veterinary teaching hospital in the United States remains undefined as well. The present study used descriptive statistics and logistic regression models to analyze feline medical records obtained at the Veterinary Medical Teaching Hospital at the University of California, Davis from January 2006 to December 2015 and to characterize the prevalence of overweight and obesity, risk factors, and disease associations. In 9,062 feline records analyzed, the overall prevalence of overweight (17.2%; n = 1,560) and obesity (23.8%; n = 2,160) was 41.0%. Neutered, male, and crossbred cats that were in age groups between 3.0 and 14.9 years old and presented with disease processes in orthopedic, dentistry, and urinary categories were positively associated with overweight and obesity. Overweight and obesity are prevalent problems, which can benefit from continual veterinary education emphasizing its importance. Structured disease surveillance plans monitoring these associated factors also help guide further research and ideally can contribute to development of better prevention strategies for overweight and obesity.

A Comparison of Key Essential Nutrients in Commercial Plant-Based Pet Foods Sold in Canada to American and European Canine and Feline Dietary Recommendations

Simple Summary

Plant-based pet foods appear to be growing in popularity, but it is unclear how suitable these products are for dogs and cats, considering both species naturally consume diets rich in, or exclusively comprised of, animal tissues. Laboratory analyses of essential nutrients were performed on 26 plant-based diets available in Ontario, Canada in 2018, including 18 canine products (13 products labelled for adult maintenance, four for all life stages, one for puppy growth), 5 feline products (two for adult maintenance and three for all life stages), and 3 products labelled for both dogs and cats (one for adult maintenance and two for all life stages). The nutrient measurements were compared to industry standard nutrient profiles. Four products met the recommendations of the Association of American Feed Control Officials and one product the nutrient recommendations of the European Pet Food Industry Federation for adult dogs. No diets met recommended nutrient content for adult cats or growing puppies or kittens. Nutrients most commonly found to be insufficient were: sulfur amino acids, taurine, arachidonic acid, EPA and DHA, calcium phosphorus and vitamin D. These nutrients are all typically found in animal tissues, though non-animal sources are available, and require careful formulation or supplementation in products made without animal-derived ingredients. Compliance with Canadian labelling regulation and guidelines was poor. These problems do not appear to be exclusive to plant-based foods and have been demonstrated previously in commercially available animal-based products as well. This study demonstrates areas where manufacturers of plant-based pet foods must improve formulation and/or manufacturing practices to produce products appropriate for feeding cats and dogs.

Abstract

Plant-based foods intended for feeding dogs and cats are available in Canada, though few studies have examined the suitability of plant-based foods for dogs and cats. All commercial plant-based extruded and wet pet food products available in Ontario, Canada, in 2018 (n = 26) were acquired and analysed for energy, crude protein, crude fat, crude fibre, ash, amino acids, fatty acids, minerals and vitamins A, B₁₂, D₂ and D₃. Results were compared with recommendations of the Association of American Feed Control Officials (AAFCO) and the European Pet Food Industry Federation (FEDIAF). Thirteen products were labelled for adult canine maintenance, four for canine all life stages, one for puppy growth, two for adult feline maintenance, three for feline all life stages, one for adult maintenance of dogs and cats and two for all life stages of dogs and cats. Four products met AAFCO and one product met FEDIAF nutrient recommendations for canine maintenance. No diets met AAFCO or FEDIAF recommendations for feline maintenance or growth for either species. Nutrients most commonly found insufficient were: sulfur amino acids, taurine, arachidonic acid, EPA and DHA, calcium phosphorus and vitamin D. There were no nutrients unable to be provided from non-animal sources. Compliance with labelling guidelines was also poor, similar to other findings with commercial animal-based pet products. The results from this study indicate areas where producers of plant-based pet foods must improve to meet the industry recommended nutrient profiles and labelling requirements.

Impact of storage temperature, storage duration, and deproteinization on plasma amino acid concentrations in dogs

Reliability of canine plasma amino acid analysis depends on sample stability which can be influenced by pre-analytical handling techniques, storage temperature, storage time, and deproteinization status. Extrapolating data to dogs from research in other species is limited given discordant methodology and interspecies differences. The present study investigated the effects of deproteinization status (non-deproteinized or deproteinized) and storage temperature (at -20 °C or - 80 °C) on the concentration of 22 canine plasma amino acids during a 300-day storage period. Storage time had a significant effect (p < 0.05) of overall declining concentration of most amino acids. Compared to non-deproteinized samples, deproteinization contributed to overall higher concentrations of cyst(e)ine and glutamic acid, and consistently modified the effect of storage time and temperature on cyst(e)ine, glutamic acid, and glutamine. Compared to -20 °C, storage at -80 °C contributed to a higher concentration of cyst(e)ine and glutamic acid, and modified the effect of storage time on arginine, glutamic acid, glutamine, and tryptophan. Storage time had a consistent, significant effect on amino acid concentrations in canine plasma samples. Although sample deproteinization and low storage temperature modified the effect of storage time, these interactions were variable among analyzed amino acids. Therefore, timely sample analysis is recommended. If delayed sample analysis is inevitable, deproteinization should be performed prior to sample banking to preserve amino acid stability.

Rabbit Carcasses for Use in Feline Diets: Amino Acid Concentrations in Fresh and Frozen Carcasses With and Without Gastrointestinal Tracts

Whole-prey diets for exotic feline species are common, and this practice has also increased in popularity for domestic cats. However, prior analyses of prey indicate possible essential amino acid inadequacy, and dilated cardiomyopathy from taurine deficiency was reported in cats fed whole ground rabbit. Crude protein, body water, and amino acid concentrations were evaluated in fresh and frozen ground rabbits with (n=10) or without (n = 10) gastrointestinal tracts. Amino acids were greater in fresh samples without gastrointestinal tracts (p < 0.05) except taurine, glycine, and cysteine. When normalized for protein content, only glutamate, alanine, methionine, isoleucine, tyrosine, lysine, histidine, and arginine were greater in fresh rabbits without gastrointestinal tracts (g/16 g N basis; p < 0.05). Freezing at -18°C for 30 days had no effect on crude protein or body water content. After freezing, only methionine was lower and only proline was higher when gastrointestinal tracts were omitted (g/16 g N basis; p < 0.05). Regardless, all essential amino acids except taurine exceeded Association of American Feed Control Officials and National Research Council nutrient recommendations for all feline life stages. In contrast, there was minimal impact of treatment on taurine concentrations. However, although feline taurine requirements for prey and other raw or fresh food diets remain undefined, none of the rabbit samples met any recommendation for taurine concentrations for commercial canned or dry extruded diets, ranging from 20 to 90% of the minimum values. Taurine supplementation is recommended when feeding rabbit to cats. Determination of taurine requirements of cats fed whole-prey diets is warranted.

Rabbit Carcasses for Use in Feline Diets: Amino Acid Concentrations in Fresh and Frozen Carcasses With and Without Gastrointestinal Tracts

Whole-prey diets for exotic feline species are common, and this practice has also increased in popularity for domestic cats. However, prior analyses of prey indicate possible essential amino acid inadequacy, and dilated cardiomyopathy from taurine deficiency was reported in cats fed whole ground rabbit. Crude protein, body water, and amino acid concentrations were evaluated in fresh and frozen ground rabbits with (n=10) or without (n = 10) gastrointestinal tracts. Amino acids were greater in fresh samples without gastrointestinal tracts (p < 0.05) except taurine, glycine, and cysteine. When normalized for protein content, only glutamate, alanine, methionine, isoleucine, tyrosine, lysine, histidine, and arginine were greater in fresh rabbits without gastrointestinal tracts (g/16 g N basis; p < 0.05). Freezing at −18°C for 30 days had no effect on crude protein or body water content. After freezing, only methionine was lower and only proline was higher when gastrointestinal tracts were omitted (g/16 g N basis; p < 0.05). Regardless, all essential amino acids except taurine exceeded Association of American Feed Control Officials and National Research Council nutrient recommendations for all feline life stages. In contrast, there was minimal impact of treatment on taurine concentrations. However, although feline taurine requirements for prey and other raw or fresh food diets remain undefined, none of the rabbit samples met any recommendation for taurine concentrations for commercial canned or dry extruded diets, ranging from 20 to 90% of the minimum values. Taurine supplementation is recommended when feeding rabbit to cats. Determination of taurine requirements of cats fed whole-prey diets is warranted.

Diet composition analysis provides new management insights for a highly specialized endangered small mammal

The critically endangered Amargosa vole (Microtus californicus scirpensis) is found only in rare marsh habitat near Tecopa, California in a plant community dominated by three-square bulrush (Schoenoplectus americanus). Since the earliest research on the Amargosa vole, the existing paradigm has been that these voles are obligatorily dependent on bulrush as their only food source and for the three-dimensional canopy and litter structure it provides for predator avoidance. However, no prior research has confirmed the diet of the Amargosa vole. In this study we characterized the Amargosa vole' nutritional needs, analyzed the quality of bulrush by forage analysis, and performed microhistological and metabarcoding analyses of vole feces to determine what foods were consumed in the wild. All bulrush plant tissues analyzed were low in fat (from 0.9% of dry matter in roots to 3.6% in seeds), high in neutral detergent fiber (from 5.9% in rhizomes to 33.6% in seeds), and low in protein (7.3-8.4%). These findings support the conclusion that bulrush alone is unlikely to support vole survival and reproduction. Fecal microhistology and DNA metabarcoding revealed relatively diverse diets including plants in 14 families, with rushes (Juncaceae), bulrushes (Cyperaceae), and grasses (Poaceae) being the most common diet items. On microhistology, all analyzed samples contained bulrush, sedges (Carex sp.), rushes (Juncus sp.), and beaked spikerush (Eleocharis rostrellata) even from marshes where non-bulrush plants were uncommon. There was evidence of insects at <1% in two marshes but none in the remaining marshes. Metabarcoding detected ten genera of plants. When considering non-Schoenoplectus targets, for which metabarcoding had poor sensitivity, saltgrass (Distichlis spicata) was the most commonly detected species, with prominent contributions from seaside arrowgrass (Triglochin concinna) and yerba mansa (Anemopsis californica) as well. Diversity of vole diets generally increased with increasing site plant diversity, but differences were not statistically significant. Confirming details about dietary behaviors is critical for informing appropriate conservation planning including habitat management and reintroduction of voles into new sites.

Development of plasma and whole blood taurine reference ranges and identification of dietary features associated with taurine deficiency and dilated cardiomyopathy in golden retrievers: A prospective, observational study

INTRODUCTION

A surge in Food and Drug Administration (FDA) consumer complaints identified concerns that legume-rich, grain-free diets were associated with nutritionally-mediated dilated cardiomyopathy (DCM). Golden retrievers represent the most reported breed affected by this condition and previous studies documented the disease is responsive to dietary change and taurine supplementation. Although dietary findings across cases are compelling, prospective studies with control groups are lacking. The role of diet in developing taurine deficiency and echocardiographic changes consistent with DCM in healthy dogs is unknown.

OBJECTIVES

We hypothesized that golden retrievers eating non-traditional diets are at a higher risk of having taurine deficiency and nutritionally-mediated DCM compared with those eating traditional commercial diets. We aimed to compare taurine concentrations and echocardiographic indices of systolic function between golden retrievers in each diet group and elucidate associations between diet and these variables. Additionally, we aimed to generate breed-specific reference intervals for whole blood and plasma taurine concentrations.

ANIMALS

86 golden retrievers.

METHODS

Golden retrievers eating traditional or non-traditional diets were evaluated and diet history, taurine concentrations and echocardiographic data were collected. Dietary features, taurine concentrations and echocardiographic findings were compared between diet groups. Relative risks were calculated for the likelihood of echocardiographic abnormalities and taurine deficiency in each diet group. Breed-specific reference intervals were constructed for taurine concentrations in dogs from the traditional diet group.

RESULTS

Golden retrievers eating non-traditional diets had significantly lower taurine concentrations and more frequent systolic dysfunction. Breed specific reference intervals are higher than previously reported across breeds.

CONCLUSIONS

Non-traditional diets, which were typically grain-free and contained legumes in this study, were significantly associated with and have increased relative risk for the identification of taurine deficiency and echocardiographic abnormalities consistent with nutritionally-mediated DCM. These findings were identifiable in the absence of clinical signs and support the findings of multiple previous studies and the ongoing FDA investigation.

Circulating nutrient concentrations in free-ranging Humboldt penguins (Spheniscus humboldti) in Punta San Juan, Peru

Free-ranging Humboldt penguin (HP, Spheniscus humboldti) populations are under pressure from resource competition with industrial fisheries, habitat loss, and El Niño Southern Oscillation events. Foraging patterns for this top marine predator change during periods of aberrant oceanographic conditions and scarce fish stock numbers. These radical dietary fluctuations can lead to poor fertility, early embryonic death, poor hatchability, suppressed immune function, high chick mortality, and illness. To understand the variability of nutrient status in reproductive seasons, we measured select circulating nutrient concentrations (fat-soluble vitamins A, D, E, and carotenoids, fatty acids, amino acids, minerals, and electrolytes) of 105 HP at Punta San Juan, Peru during the first reproductive seasons of 2007 and 2008. We determined significant differences in nutrient status between sexes, years of sampling, and reproductive stages. Males (4.5 ± 0.38 kg) weighed more than females (4.0 ± 0.29 kg) and exhibited higher concentrations of vitamin A (0.71 ± 0.11 vs. 0.61 ± 0.12 µg/ml) and docosahexaenoic acid (6.70 ± 1.61 vs. 5.65 ± 1.59%). Males also displayed lower concentrations of β-carotene (0.01 ± 0.01 vs. 0.012 ± 0.001 µg/ml) and phosphorus (3.43 ± 0.83 vs. 4.40 ± 1.66 mg/dl). Comparison between the 2 years showed most circulating amino acid concentrations were higher in 2007. Significant differences in circulating amino acids and vitamins were also noted between different reproductive stages. These results demonstrate concentrations of nutrients can vary due to the physiological state of the animal, as well as the overall dynamics of their marine ecosystem habitat.

Determination of Total Mercury and Methylmercury Concentrations in Commercial Canine Diets

Methylmercury is an organic form of mercury that is well recognized for its bioaccumulation in aquatic species. Consumption of fish contaminated with methylmercury poses a toxicological health risk to both humans and animals. Salmon is an increasingly common ingredient in commercial pet foods because of manufacturers' interest in unconventional protein sources and inclusion of omega-3 polyunsaturated fatty acids. Previous studies have measured total mercury, but not methylmercury, in commercial pet foods. The purpose of this study was to evaluate total mercury and methylmercury concentrations in commercially available salmon-containing and nonsalmon-containing canine diets and to estimate risk of chronic exposure in dogs fed these diets long term. Total mercury was detected in 3 of 24 diets evaluated (12.5%), 2 of which did not contain any ingredients from fish. The single salmon-containing diet that contained total mercury was the lowest of the 3 but was also the only sample positive for methylmercury. None of the 3 mercury-containing diets contained fish oil. Concentrations of total mercury were similar to most data previously reported for pet foods. Using expected calorie intake for dogs of 2 body weights, the mercury concentrations determined in this study were applied to theoretical chronic exposure calculations to assess risk of toxicosis to dogs. Total mercury and methylmercury were uncommonly identified in the commercially available canine diets sampled in this study and were found in concentrations unlikely to pose risk to healthy adult dogs. Common sources of mercury in pet foods remain unknown and are not reliably of seafood origin.

Amino acid status in dogs with protein-losing nephropathy

Background

Proteinuria in dogs with kidney disease can contribute to protein‐energy wasting and malnutrition. Little is known about amino acid (AA) status in dogs with protein‐losing nephropathy (PLN).

Objectives

The purpose of our study was to further elucidate AA status in PLN dogs, with the hypothesis that PLN dogs would have altered AA status as compared to healthy dogs.

Animals

Thirty client‐owned PLN dogs were compared to 10 healthy control dogs.

Methods

Prospective observational study. Dogs with PLN that were presented to the teaching hospital were enrolled. Plasma AA profiles were measured using an automated high‐performance liquid chromatography AA analyzer.

Results

Compared to control dogs, PLN dogs had significantly lower concentrations of leucine, threonine, histidine, glycine, proline, asparagine, tyrosine, o‐hydroxyproline, and serine, as well as sums of both essential and nonessential AA (P < .05). Dogs with PLN had significantly lower ratios of tyrosine‐to‐phenylalanine and glycine‐to‐serine (P < .05), and a significantly greater ratio of valine‐to‐glycine (P < .05).

Conclusions and Clinical Importance

Dogs with PLN have altered AA status compared to healthy dogs. These findings could have therapeutic implications in determining optimal management of PLN dogs, such as providing AA supplementation along with other standard treatment.

Correction: Taurine deficiency and dilated cardiomyopathy in golden retrievers fed commercial diets

[This corrects the article DOI: 10.1371/journal.pone.0209112.].

Taurine deficiency and dilated cardiomyopathy in golden retrievers fed commercial diets

INTRODUCTION

Golden retrievers are over-represented in cases of taurine-deficient dilated cardiomyopathy and recently a surge in cases has prompted further investigation.

OBJECTIVE

To describe the clinical, dietary, and echocardiographic features in golden retrievers diagnosed with taurine deficiency and dilated cardiomyopathy, and to determine specific dietary associations. A second aim was to determine the whole blood taurine concentrations in a representative sample of healthy golden retrievers.

ANIMALS

Twenty-four client-owned golden retrievers with documented taurine deficiency and dilated cardiomyopathy and 52 healthy client-owned golden retrievers.

METHODS

In this multicenter prospective observational study, baseline and follow-up echocardiographic data, complete diet and medical histories, and whole blood, plasma, or serum taurine concentrations were obtained. Baseline and follow-up echocardiographic data were compared. Associations were evaluated between specific diets and taurine deficiency or congestive heart failure. The prevalence of low whole blood taurine concentrations in the healthy golden retrievers was calculated.

RESULTS

Twenty-three of 24 dogs diagnosed with taurine deficiency and dilated cardiomyopathy were fed diets that were either grain-free, legume-rich, or a combination of these factors. None of these diets were feeding trial tested using Association of American Feed Control Officials (AAFCO) procedures. Twenty-three of 24 dogs had significant improvement in their echocardiographic parameters and normalization of taurine concentrations following diet change and taurine supplementation. Nine of 11 dogs diagnosed with congestive heart failure (CHF) had resolution of their congestion at follow-up with five no longer requiring diuretic therapy and four tolerating diuretic dose reduction by >50%.

CONCLUSIONS

Certain diets and diet characteristics were associated with the development of taurine deficiency. Taurine deficiency and dilated cardiomyopathy in golden retrievers is likely multifactorial, including a combination of dietary, metabolic, and genetic factors.

Determination of mammalian DNA in commercial canine diets with uncommon and limited ingredients

Over‐the‐counter (OTC) limited ingredient canine diets could be reliable alternatives to veterinary therapeutic formulations for the diagnosis and management of adverse food reaction (AFR). However, the possibility of undeclared ingredients jeopardizes the efficacious use of OTC options for medical purposes. The objective was to determine the presence of undeclared ingredients in OTC canine dry diets marketed as limited or single protein source diets. Twenty‐one OTC adult canine diets marketed as limited or single protein source diets were purchased. Multiplex PCR was used to screen for DNA of 10 mammalian species with species‐specific primers that anneal to regions of the mitochondrial cytochrome b gene. The presence of DNA from one or more species not declared on the label was identified in all 21 diets: cow (Bos taurus), pig (Sus scrofa), sheep (Ovis sp.), goat (Capra hircus) and bison (Bison bison). Twenty diets were positive for the declared protein source and one diet was negative for the declared species. Cat (Felis catus), dog (Canis sp.), horse (Equus sp.), mouse (Mus musculus) and rat (Rattus norvegicus) DNA was not identified in any samples. The presence of undeclared mammal species in OTC canine dry diets marketed as having limited or single protein source ingredients may complicate AFR diagnosis and treatment. However, PCR can detect a miniscule amount of DNA which might not be clinically significant, because the amount needed to elicit a response is unknown. Quantification of the contamination was not determined in this study, precluding discrimination of intentional adulteration from unavoidable cross‐contamination.

Longitudinal changes in blood metabolites, amino acid profile, and oxidative stress markers in American Foxhounds fed a nutrient-fortified diet

The objective of the present study was to evaluate the changes in blood metabolites, AA profile, and oxidative stress markers in American Foxhound dogs fed a nutrient-fortified endurance diet while undergoing unstructured endurance exercise over several months. Thirty-six adult American Foxhound dogs (mean age: 4.5, range 2 to 10 yr and mean BW: 34.7, range: 23.1 to 46.9 kg) were selected to participate in the study. Prior to the study, all dogs consumed a commercial diet for 16 wk. After collecting baseline blood samples, dogs were assigned to a standard commercial performance diet (control) or a nutrient-fortified dog food (test). Dogs were balanced by gender, age, body weight, and athletic performance between diets. During the study, dogs underwent 78 bouts of exercise, with approximately 22 km/bout. Blood samples were collected after 40, 75, 138, and 201 d on study (October 2012 to March 2013). All blood metabolites were similar at baseline and serum chemistry profile remained within normal ranges throughout the study. Over time, plasma taurine and vitamin E concentrations decreased (P < 0.05) in dogs fed the control diet but were maintained or increased (P < 0.05) in dogs fed the treatment diet. Also, plasma creatinine and triglycerides were lower (P < 0.05) and blood phosphorus and alkaline phosphatase were higher (P < 0.05) in dogs fed the treatment diet. Vitamin E and taurine status of dogs appear to be affected by extended endurance exercise. These data suggest dogs undergoing endurance exercise may benefit from supplementation of vitamin E and taurine to minimize oxidation and maintain taurine status.

Alterations in serum amino acid concentrations in dogs with protein-losing enteropathy

BACKGROUND

Certain amino acids are decreased in humans with inflammatory bowel disease (IBD) and supplementation with the same amino acids has shown beneficial effects in animal models of IBD. Currently, the amino acid status of dogs with protein-losing enteropathy (PLE) is unknown.

HYPOTHESIS/OBJECTIVE

To determine if serum amino acid concentrations are abnormal in dogs with PLE and correlated with clinical and laboratory variables and outcome.

ANIMALS

Thirty client-owned dogs diagnosed with PLE and 12 apparently healthy dogs seen at Bristol Veterinary School.

METHODS

Retrospective study using stored residual serum from fasted dogs with PLE, collected at the time of diagnostic investigation and from apparently healthy dogs. Serum was analyzed for 30 amino acids using an automated high-performance liquid chromatography amino acid analyzer.

RESULTS

Serum tryptophan concentrations were significantly decreased in dogs with PLE (median, 22 nmol/mL; range, 1-80 nmol/mL) compared with apparently healthy control dogs (median, 77.5 nmol/mL; range, 42-135 nmol/mL, P < .001). There were no significant differences in the remaining 29 serum amino acids between dogs with PLE and apparently healthy. Serum tryptophan concentrations were also significantly correlated with serum albumin concentrations in dogs with PLE (P = .001, R² = 0.506).

CONCLUSIONS AND CLINICAL IMPORTANCE

Decreased serum tryptophan concentration might play a role in the pathogenesis of canine PLE or be a consequence of the disease.

A descriptive pilot study of cytokine production following stimulation of ex-vivo whole blood with commercial therapeutic feline hydrolyzed diets in individual healthy immunotolerant cats

Background

Hydrolyzed diets are used in companion animals for the diagnosis and treatment of adverse food reaction. Similarly, hydrolyzed formulas are used in human infants with severe inflammatory bowel disease or milk allergy, and these must meet the standard of hypoallergenicity through rigorous testing. Unfortunately, no standards are currently applied to hydrolyzed veterinary therapeutic diets, and data for the immunogenicity of feline diets is also not available. Therefore, the main aim of this pilot study was to determine if ex-vivo whole blood stimulation assays could be used to characterize the cytokine response to hydrolyzed commercial diets in a small number of individual healthy immunotolerant cats. This approach has also been used to investigate cytokine production in response to cow milk protein in humans and currently similar studies do not exist in companion animals. Nine healthy cats previously eating the same basal diet were divided into groups and fed one of three hydrolyzed diets exclusively for 6 weeks. Heparinized whole blood was collected from each cat before and after the feeding trial. Ex-vivo whole blood stimulation assays were performed using crude extracts of the basal diet as a positive control, as this diet contained the same proteins present in the hydrolyzed diet but were intact, saline as a negative control, and each cat’s respective hydrolyzed diet. Supernatants were collected and analyzed for tumor necrosis factor-alpha, interleukin-10 (IL-10), and interleukin-4 using enzyme-linked immunosorbant assay.

Results

Seven cats produced detectable amounts of the anti-inflammatory cytokine IL-10 upon stimulation with the basal diet. Two cats produced detectable amounts of IL-10 upon stimulation with a hydrolyzed soy-based diet and one cat produced a detectable amount of IL-10 upon stimulation with a hydrolyzed chicken-based diet (>125 pg/mL).

Conclusions

Results from this pilot study suggest that in some healthy immunotolerant cats, some hydrolyzed diets may elicit a similar cytokine response compared to their basal diet, which contained the same proteins intact. Therefore, animals may be able to recognize and react to some hydrolyzed forms of tolerated proteins, and may also suggest IL-10 as a target for investigation as a potential marker for dietary tolerance in cats, however further studies would be necessary to corroborate this. Further studies are also needed to determine if this would also be the same in immunologically naïve, sensitized and clinically hypersensitized cats.

Whole-Blood Taurine Concentrations in Cats With Intestinal Disease

Background

Increased delivery of taurine‐conjugated bile acids to the distal bowel can lead to dysbiosis resulting in colitis in mouse models of inflammatory bowel disease. A similar situation also could occur in cats with intestinal disease and might therefore result in decreased whole‐body taurine concentration.

Hypothesis/Objectives

To determine whether whole‐blood taurine concentrations are decreased at the time of diagnosis in cats with intestinal disease and to correlate concentrations with clinical and laboratory variables.

Animals

Twenty‐one cats with chronic inflammatory enteropathy and 7 cats with intestinal neoplasia from the University of Bristol.

Methods

Cats that had undergone a thorough investigation consisting of a CBC, serum biochemistry, serum cobalamin and folate concentrations, transabdominal ultrasound examination and histopathology of intestinal biopsy specimens, as well as additional testing if indicated, were included. Whole‐blood from these cats collected at the time of histologic diagnosis and stored in ethylenediaminetetraacetic acid was retrospectively analyzed for taurine with an automated high‐performance liquid chromatography amino acid analyzer.

Results

Although whole‐blood taurine concentrations remained within the reference range, those cats with predominantly large intestinal clinical signs had significantly lower concentrations than did cats with small intestinal and mixed bowel clinical signs (P = 0.033) and this difference also was significant when assessed only in cats with chronic inflammatory enteropathy (P = 0.019).

Conclusions and Clinical Importance

Additional studies are needed to determine whether large intestinal signs in cats with chronic inflammatory enteropathy are caused by alterations in the microbiota arising as a consequence of increased delivery of taurine‐conjugated bile acids.

Impact of hyperlipidaemia on intermediary metabolism, faecal microbial metabolites and urinary characteristics of lipoprotein lipase deficient vs. normal cats

Findings in humans and rats indicate that hyperlipidaemia may be associated with enhanced endogenous oxalate (Ox) synthesis, which may be relevant for calcium oxalate (CaOx) urolith formation. Moreover, changes in lipid metabolism are proposed to negatively affect gut microbiota. This study aimed to investigate those potential interactions in hyperlipidaemic cats. Therefore, 10 normal control cats and seven lipoprotein lipase (LPL)-deficient cats were fed a low-fat diet for seven weeks. During the last week of the study, cats were housed in metabolic cages to collect urine and faeces. Blood was taken on the last day of the study. The LPL-deficient cats had significantly higher serum triglyceride concentrations than normal cats, while lactate dehydrogenase (LDH) activity was not different. Urinary relative supersaturation with CaOx, urinary Ox, calcium, and citrate excretions, and urine pH did not differ between groups. Lower faecal acetic, propionic and total short-chain fatty acid concentrations were observed in the LPL-deficient cats. In conclusion, hyperlipidaemia does not appear to be a specific risk factor for CaOx urolith formation in cats. In contrast to results in rats, hyperlipidaemia was not accompanied by elevated serum LDH activity. As LDH can synthesise Ox from glycolate or other precursors, this might be one possible explanation for the similar urinary parameters in the LPL-deficient and normal cats. Non-diet-induced hyperlipidaemia was not associated with marked changes in faecal microbial metabolites, suggesting no differences in the composition of the intestinal microbiota.

Evaluation of dogs with genetic hyperuricosuria and urate urolithiasis consuming a purine restricted diet: a pilot study

Background

Urate urolithiasis is a common problem in breed homozygous for the mutation that results in hyperuricosuria. Low purine diets have been recommended to reduce purine intake in these dogs.

Methods

A higher protein, purine restricted diet with water added was evaluated in dogs with genetic hyperuricosuria and a history of clinical urate urolithiasis over a one year time period. Dogs were evaluated at baseline and 2, 6, and 12 months after initiating the test diet. Bloodwork, urinalysis, abdominal ultrasound, body composition, and 24-h urinary purine metabolite analyses were performed.

Results

Transient, mild, self-limited lower urinary tract signs were noted in only one dog on a single day, despite variable but usually mild and occasionally moderate amounts of echogenic bladder stones (<2-3 mm in size) in almost every dog at each visit. No significant differences were noted in urine specific gravity, urine pH, lean body condition score or body composition. Urinary uric acid concentration was lower on the test diet (p = 0.008), but 24-h uric acid excretions were similar (p = 0.220) compared to baseline. Significant differences between least squares mean plasma amino acid concentrations measured at the 0 and 12-month visits were found only for valine (p = 0.0119) and leucine (p = 0.0017).

Conclusion

This study suggests the use of a low purine, higher protein diet with added water may be beneficial as part of the management of dogs with genetic hyperuricosuria and history of clinical urate urolithiasis.

Electronic supplementary material

The online version of this article (doi:10.1186/s12917-017-0958-y) contains supplementary material, which is available to authorized users.

Effects of dietary lysine supplementation in cats with enzootic upper respiratory disease

To determine the effectiveness of dietary lysine supplementation in cats with enzootic upper respiratory disease (URD), 50 cats were fed a ration containing 11 or 51 g lysine/kg diet for 52 days. Food intake, body weight, clinical signs, plasma amino acid concentrations and presence of Chlamydophila felis or feline herpesvirus (FHV)-1 DNA within the conjunctival fornix were assessed. Food and lysine intake of both dietary groups decreased between days 17 and 22, coinciding with peak disease and viral presence. Mean disease score for cats fed the supplemented ration (0.94) was higher than for those fed the basal diet (0.21); however, this could be attributed to a small subset of male cats which demonstrated fighting behavior that may have contributed to stress within that cage. FHV-1 DNA was detected on 12 occasions in six cats receiving the supplemented diet and on one occasion in one cat fed the basal diet. C felis DNA was never detected. Mean plasma arginine concentration was lower and plasma lysine concentration was higher in supplemented cats. Mean plasma arginine concentration declined throughout the study in both dietary groups. Data from the present study raise important questions but do not permit a definitive conclusion regarding the efficacy of dietary lysine supplementation in cats with enzootic URD.

Meeting the Vitamin A Requirement: The Efficacy and Importance of β-Carotene in Animal Species

Vitamin A is essential for life in all vertebrate animals. Vitamin A requirement can be met from dietary preformed vitamin A or provitamin A carotenoids, the most important of which is β-carotene. The metabolism of β-carotene, including its intestinal absorption, accumulation in tissues, and conversion to vitamin A, varies widely across animal species and determines the role that β-carotene plays in meeting vitamin A requirement. This review begins with a brief discussion of vitamin A, with an emphasis on species differences in metabolism. A more detailed discussion of β-carotene follows, with a focus on factors impacting bioavailability and its conversion to vitamin A. Finally, the literature on how animals utilize β-carotene is reviewed individually for several species and classes of animals. We conclude that β-carotene conversion to vitamin A is variable and dependent on a number of factors, which are important to consider in the formulation and assessment of diets. Omnivores and herbivores are more efficient at converting β-carotene to vitamin A than carnivores. Absorption and accumulation of β-carotene in tissues vary with species and are poorly understood. More comparative and mechanistic studies are required in this area to improve the understanding of β-carotene metabolism.

Dietary beet pulp decreases taurine status in dogs fed low protein diet

Background

It is known that large dogs who are fed lamb and rice diets are at increased risk to develop taurine-deficiency-induced dilated cardiomyopathy. Since dogs obligatorily conjugate bile acids (BA) with taurine, we determined whether rice bran (RB) or other fibers (cellulose; CL, beet pulp; BP) would affect BA excretion and/or the taurine status of dogs.

Results

Eighteen medium/large mixed-breed dogs were given purified diets containing CL, BP, or RB for 12 weeks. Taurine concentrations in plasma and whole blood were significantly decreased at week 12. The BP group, compared to the CL or RB groups, showed significantly lower taurine concentrations in plasma (6.5 ± 0.5 vs 20.4 ± 3.9 and 13.1 ± 2.0 μmol/L, respectively, P < 0.01, mean ± SEM) and in whole blood (79 ± 10 vs 143 ± 14 and 127 ± 14 μmol/L, respectively, P < 0.01), lower apparent protein digestibility (81.9 ± 0.6 vs 88.8 ± 0.6 and 88.1 ± 1.2 %, respectively, P < 0.01), and higher BA excretions (5.6 ± 0.1 vs 3.4 ± 0.5 and 3.4 ± 0.4 μmol/g feces, respectively, P < 0.05) at week 12.

Conclusions

These results do not support the hypothesis that RB is likely to be a primary cause of lamb meal and rice diets, increasing the risk of taurine deficiency in large dogs. However these indicate that BP may contribute to a decrease taurine status in dogs by increasing excretion of fecal BA and decreasing protein digestibility, thus decreasing the bioavailability of sulfur amino acids, the precursors of taurine.

Assessment of protein and amino acid concentrations and labeling adequacy of commercial vegetarian diets formulated for dogs and cats

OBJECTIVE

To determine measured crude protein (CP) and amino acid (AA) concentrations and assess labeling adequacy of vegetarian diets formulated for dogs and cats.

DESIGN

Cross-sectional study.

SAMPLE

13 dry and 11 canned vegetarian diets for dogs and cats.

PROCEDURES

Concentrations of CP and AAs were determined for each diet. Values were compared with the Association of American Feed Control Officials (AAFCO) Dog and Cat Food Nutrient Profiles. Product labels were assessed for compliance with AAFCO regulations.

RESULTS

CP concentration (dry-matter basis) ranged from 19.2% to 40.3% (median, 29.8%). Minimum CP concentrations for the specified species and life stage were met by 23 diets; the remaining diet passed appropriate AAFCO feeding trials. Six diets did not meet all AA minimums, compared with the AAFCO nutrient profiles. Of these 6 diets, 1 was below AAFCO minimum requirements in 4 AAs (leucine, methionine, methionine-cystine, and taurine), 2 were below in 3 AAs (methionine, methionine-cystine, and taurine), 2 were below in 2 AAs (lysine and tryptophan), and 1 was below in 1 AA (tryptophan). Only 3 and 8 diets (with and without a statement of calorie content as a requirement, respectively) were compliant with all pet food label regulations established by the AAFCO.

CONCLUSION AND CLINICAL RELEVANCE

Most diets assessed in this study were not compliant with AAFCO labeling regulations, and there were concerns regarding adequacy of AA content. Manufacturers should ensure regulatory compliance and nutritional adequacy of all diets, and pets fed commercially available vegetarian diets should be monitored and assessed routinely.

Effect of short-term probiotic Enterococcus faecium SF68 dietary supplementation in overweight and obese cats without comorbidities

Obesity in cats is associated with metabolic abnormalities and increased susceptibility to diseases such as diabetes mellitus. Studies in mouse models and human beings have shown that probiotics can reduce food intake, promote weight loss and improve metabolic profile. Studies assessing the effects of probiotics on these same parameters are absent in cats. Therefore, the aim of this study was to determine if probiotic Enterococcus faecium strain SF68 dietary supplementation reduces food intake, promotes weight loss and improves metabolic profile in overweight and obese cats without comorbidities. Twenty overweight and obese specific pathogen-free cats without comorbidities were acclimatised to a dry diet for four weeks. After exclusion of four cats for unrelated reasons, eight cats received a daily oral probiotic for eight weeks and eight control cats received no probiotic. All cats were fed ad libitum with food intake measured daily and bodyweight weekly. Blood was collected at three time points: after four weeks of acclimatisation to the diet, after eight weeks of intervention and after six weeks of washout for measurement of glucose, triglyceride, cholesterol, fructosamine, insulin, leptin, total adiponectin and deuterium oxide for body composition. There were no differences in food intake, metabolic parameters and body composition between the probiotic and control groups after eight weeks of intervention and six weeks of washout (P≥0.050). Short-term use of E faecium SF68 dietary supplementation had no significant effect on food intake, bodyweight, body composition or metabolic parameters in overweight and obese specific pathogen-free cats without comorbidities.

Determination of mammalian deoxyribonucleic acid (DNA) in commercial vegetarian and vegan diets for dogs and cats

The determination of undeclared ingredients in pet food using different analytical methods has been reported in recent years, raising concerns regarding adequate quality control, dietary efficacy and the potential for purposeful adulteration. The objective of this study was to determine the presence or absence of mammalian DNA using multiplex polymerase chain reaction (PCR) on diets marketed as vegetarian or vegan for dogs and cats. The diets were tested in duplicate; two samples were purchased approximately 3 to 4 months apart with different lot numbers. Multiplex PCR-targeted mitochondrial DNA with two species-specific primers was used to amplify and sequence two sections of the cytochrome b gene for each of the 11 mammalian species. Half of the diets assessed (7/14) were positive for one or more undeclared mammalian DNA source (bovine, porcine, or ovine), and the result was repeatable for one or more species in six diets. While most of the detected DNA was found at both time points, in some cases, the result was positive only at one time point, suggesting the presence may have been due to unintentional cross-contact with animal-sourced ingredients. DNA from feline, cervine, canine, caprine, equine, murine (mouse and rat) and leporine was not identified in any samples. However, evidence of mammalian DNA does not confirm adulteration by the manufacturer nor elucidate its clinical significance when consumed by animals that may benefit from a vegetarian or vegan diet.

Evaluation of total dietary fiber concentration and composition of commercial diets used for management of diabetes mellitus, obesity, and dietary fat-responsive disease in dogs

OBJECTIVE

To determine total dietary fiber (TDF) concentration and composition of commercial diets used for management of obesity, diabetes mellitus, and dietary fat-responsive disease in dogs.

DESIGN

Cross-sectional study.

SAMPLE

Dry (n = 11) and canned (8) canine therapeutic diets.

PROCEDURES

Insoluble and soluble dietary fiber (IDF and SDF), high-molecular-weight SDF (HMWSDF), and low-molecular-weight SDF (LMWSDF) concentrations were determined. Variables were compared among diets categorized by product guide indication, formulation (dry vs canned), and regulatory criteria for light and low-fat diets.

RESULTS

SDF (HMWSDF and LMWSDF) comprised a median of 30.4% (range, 9.4% to 53.7%) of TDF; LMWSDF contributed a median of 11.5% (range, 2.7% to 33.8%) of TDF. Diets for diabetes management had higher concentrations of IDF and TDF with lower proportions of SDF and LMWSDF contributing to TDF, compared with diets for treatment of fat-responsive disease. Fiber concentrations varied within diet categories and between canned and dry versions of the same diet (same name and manufacturer) for all pairs evaluated. Diets classified as light contained higher TDF and IDF concentrations than did non-light diets. All canned diets were classified as low fat, despite providing up to 38% of calories as fat.

CONCLUSIONS AND CLINICAL RELEVANCE

Diets provided a range of TDF concentrations and compositions; veterinarians should request TDF data from manufacturers, if not otherwise available. Consistent responses to dry and canned versions of the same diet cannot necessarily be expected, and diets with the same indications may not perform similarly. Many diets may not provide adequate fat restriction for treatment of dietary fat-responsive disease.

The effect of 48-hour fasting on taurine status in healthy adult dogs

Low circulating taurine concentrations may be a risk factor for dilated cardiomyopathy (DCM) in dogs. Circulating taurine is typically measured in the clinic 4-5 h after feeding, largely because the impact of later sampling is not known. The objective of this study was to measure taurine in the blood during a 48-h fast in 12 healthy adult Labrador Retrievers to refine sampling methodology for determination of taurine status. Plasma and whole blood (WB) taurine concentrations did not fall to levels indicative of clinical deficiency throughout fasting; WB was the more reliable indicator of taurine status. This study shows that blood samples can be taken for assessment of taurine status any time up to 48 h after ingestion of a meal in healthy adult dogs.

Total dietary fiber composition of diets used for management of obesity and diabetes mellitus in cats

OBJECTIVE

To determine total dietary fiber (TDF) composition of feline diets used for management of obesity and diabetes mellitus.

DESIGN

Cross-sectional survey.

SAMPLE

Dry veterinary (n = 10), canned veterinary (12), and canned over-the-counter (3) feline diets.

PROCEDURES

Percentage of TDF as insoluble dietary fiber (IDF), high-molecular-weight soluble dietary fiber (HMWSDF), and low-molecular-weight soluble dietary fiber (LMWSDF) was determined.

RESULTS

Median measured TDF concentration was greater than reported maximum crude fiber content in dry and canned diets. Median TDF (dry-matter) concentration in dry and canned diets was 12.2% (range, 8.11% to 27.16%) and 13.8% (range, 4.7% to 27.9%), respectively. Dry and canned diets, and diets with and without a source of oligosaccharides in the ingredient list, were not different in energy density or concentrations of TDF, IDF, HMWSDF, or LMWSDF. Similarly, loaf-type (n = 11) and gravy-type (4) canned diets differed only in LMWSDF concentration. Disparities in TDF concentrations among products existed despite a lack of differences among groups. Limited differences in TDF concentration and dietary fiber composition were detected when diets were compared on the basis of carbohydrate concentration. Diets labeled for management of obesity were higher in TDF concentration and lower in energy density than diets for management of diabetes mellitus.

CONCLUSIONS AND CLINICAL RELEVANCE

Diets provided a range of TDF concentrations with variable concentrations of IDF, HMWSDF, and LMWSDF. Crude fiber concentration was not a reliable indicator of TDF concentration or dietary fiber composition. Because carbohydrate content is calculated as a difference, results suggested that use of crude fiber content would cause overestimation of both carbohydrate and energy content of diets.

Comparison of the nutrient composition of commercial dog milk replacers with that of dog milk

OBJECTIVE

To compare the nutrient composition of commercially available dog milk replacers with that of dog milk.

DESIGN

Prospective, cross-sectional study.

SAMPLE

5 dog milk samples and 15 samples of commercial dog milk replacers.

PROCEDURES

Dog milk and milk replacers were analyzed for concentrations of total protein, essential amino acids, sugars, total fat, essential fatty acids, calcium, and phosphorus. Energy density was calculated. Results from milk replacers were compared with the range of the concentration of each nutrient in milk samples from mature dogs as well as the National Research Council (NRC) recommendations for puppy growth.

RESULTS

Milk replacers varied widely in caloric density and concentration of nutrients such as calcium, protein, and fat. Calcium concentration was lower in 14 of 15 milk replacers than in the dog milk samples. Docosahexaenoic acid was undetectable in 12 of 15 milk replacers but present in all dog milk samples. All milk replacers had numerous essential nutrients outside of the range of the dog milk samples, and many had concentrations of amino acids, essential fatty acids, calcium, and phosphorus less than the NRC minimal requirement or recommended allowance. Compared with NRC recommendations, some dog milk samples had concentrations of total protein, linoleic acid, calcium, or phosphorus less than the recommended allowance.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggested that there was substantial variation in nutrient composition of 15 dog milk replacers and that some products were closer approximations of dog milk than others. Nearly all products would benefit from more appropriate calcium, amino acids, and essential fatty acids concentrations and better feeding directions.

Macronutrients in feline health

Dietary macronutrients include protein, fat, and carbohydrates. Current nutritional recommendations establish minimums but not maximums for protein and fat but not for carbohydrates; thus, commercial feline maintenance diets have a wide range of macronutrient distribution depending on manufacturer, ingredients, and processing. There is growing interest and discussion, however, in defining the ideal macronutrient composition of feline diets to maximize longevity and health. Current recommendations should be tailored to each patient based on age, body condition, presence of muscle mass atrophy, and the presence of disease.

Influence of dietary protein level on body composition and energy expenditure in calorically restricted overweight cats

High-protein (HP) diets help prevent loss of lean mass in calorie-restricted (CR) cats. However, it is not entirely known whether these diets also induce changes of energy expenditure during periods of CR. To investigate this issue, sixteen overweight cats were fed either a high-protein [(HP), 54.2% of metabolizable energy (ME)] or a moderate-protein [(MP), 31.5% of ME] diet at 70% of their maintenance energy intakes for 8 weeks, and energy expenditure, energy intake, body weight and composition, and serum metabolites and hormones were measured. While both groups of cats lost weight at a similar rate, only cats eating the HP diet maintained lean mass during weight loss. Indirect respiration calorimetry measurements revealed that both total and resting energy expenditure (kcal/d) significantly decreased during weight loss for both treatment groups. However, only cats eating the MP diet exhibited significant decreases of total and resting energy expenditures after energy expenditure was normalized for body weight or lean mass. Results from this study suggest that in addition to sparing the loss of lean mass, feeding HP diets to overweight cats in restricted amounts may be beneficial for preventing or minimizing decreases of mass-adjusted energy expenditure during weight loss.

Early effects of neutering on energy expenditure in adult male cats

The initial cause of post-neutering weight gain in male cats is not entirely known. There is evidence that energy intake (EI) increases rapidly post-neutering, but it is not clear if neutering also decreases energy expenditure (EE) prior to weight gain. Thus, the purpose of this study was to determine if a decrease in EE contributes to the initial shift toward positive energy balance in neutered male cats. To determine the influence of neutering on EE independent of changes in EI and body weight (BW), male cats were fed at their pre-neutering maintenance EI and EE was measured at 4 days pre-neutering, 3–4 days post-neutering, and 9 days post- neutering. Ad libitum food access was then provided for 6 months. Body composition was measured and blood samples collected for serum chemistry at pre-neutering and 7 days, 13 days and 6 months post-neutering. Total energy expenditure (TEE) adjusted for lean body mass (LBM) did not change in cats from pre-neutering to 9 days post-neutering. However, TEE adjusted for BW and resting energy expenditure adjusted for either LBM or BW showed a small, but significant (P<0.05) increase from pre-neutering to 9 days post-neutering. When allowed free choice food access, cats showed significant increases of food intake (FI) and BW. Circulating concentrations of ghrelin increased, while adiponectin levels decreased following neutering. The results of this study indicate that initial post-neutering weight gain in male cats results from increased FI and not decreased EE. Long-term control of FI should be initiated after neutering to prevent hyperphagia and weight gain in male cats.

Evaluation of fiber concentration in dry and canned commercial diets formulated for adult maintenance or all life stages of dogs by use of crude fiber and total dietary fiber methods

OBJECTIVE

To assess differences among reported maximum crude fiber (CF), measured CF, and measured total dietary fiber (TDF) concentrations, and determine fiber composition in dry and canned nontherapeutic diets formulated for adult maintenance or all life stages of dogs.

DESIGN

Prospective cross-sectional study.

SAMPLE

Dry (n = 20) and canned (20) nontherapeutic canine diets.

PROCEDURES

Reported maximum CF concentrations were obtained from product labels. Concentrations of CF and TDF were measured in samples of the diets for comparison. For each diet, percentages of TDF represented by insoluble dietary fiber (IDF) and soluble dietary fiber (SDF) were determined.

RESULTS

For dry or canned diets, the median reported maximum CF concentration was significantly greater than the median measured value. Measured CF concentration was significantly lower than measured TDF concentration for all diets. Median percentage of TDF (dry-matter basis) in dry and canned diets was 10.3% and 6.5%, respectively (overall range, 3.9% to 25.8%). Fiber composition in dry and canned diets differed; median percentage of TDF provided by IDF (dry-matter basis) was 83.4% in dry diets and 63.6% in canned diets.

CONCLUSIONS AND CLINICAL RELEVANCE

Among the evaluated diets, measured CF concentration underrepresented measured TDF concentration. Diets provided a wide range of TDF concentration, and proportions of IDF and SDF were variable. In the absence of information regarding TDF concentration, neither reported maximum nor measured CF concentration appears to be a particularly reliable indicator of fiber concentration and composition of a given canine diet.

Body composition and amino acid concentrations of select birds and mammals consumed by cats in northern and central California

The diet of the feral domestic cat consists of primarily birds and small mammals, but the nutritional composition is relatively unknown. Because of the increasing popularity of natural diets for cats and other wild captive carnivores, the purpose of this study was to describe the body composition and AA concentrations of select birds and small mammals in northern and central California: wild-caught mice (n = 7), Norway rats (n = 2), roof rats (n = 2), voles (n = 4), moles (n = 2), gophers (n = 3), and birds (n = 4). Body water, crude fat (CFa), CP, ash, and AA composition for each specimen were determined. Results are reported as mean ± SD. All results are reported on a DM basis except body water (as-is basis) and AA (g/16 g N). Combined, carcasses had this mean composition: 67.35 ± 3.19% water, 11.72 ± 6.17% CFa, 62.19 ± 7.28% CP, and 14.83 ± 2.66% ash. Concentrations of Arg, Tau, Cys, and Met were 5.63 ± 0.46, 0.92 ± 0.33, 1.91 ± 0.89, and 1.82 ± 0.19 g/16 g N, respectively. Using NRC physiologic fuel values for CP, CFa, and carbohydrate by difference, the combined average energy content of the carcasses was 3,929 kcal/kg DM, but the fiber content was not determined. With the exception of mice and rats, little historical data exist regarding the body and AA composition of many of the species analyzed in this study. Wild-caught mice and rats were composed of less fat but more ash compared with previously reported data in their purpose-bred counterparts. The CP content of mice in this study was similar to previous reports in purpose-bred mice. The CP content of rats was similar or slightly greater compared with historical findings in purpose-bred rats. The N content of rats and AA concentrations on a per-N basis for both rats and mice were similar to previously published data on purpose-bred rodents. The discrepancies in nutrient composition, especially fat concentration, indicate that using purpose-bred animals to represent the diet of the feral domestic cat may not be valid in many instances. When consumed to meet energy needs, the nutrient content of the species reported in the present study exceed the NRC (2006) recommended allowances (RA) for total fat, CP, and essential AA for felines at all life stages.

Evaluation of recipes for home-prepared diets for dogs and cats with chronic kidney disease

OBJECTIVE

To evaluate recipes of diets recommended for animals with chronic kidney disease (CKD), compare nutritional profiles for those recipes to requirements for adult dogs and cats, and assess their appropriateness for the management of CKD.

DESIGN

Evaluation study.

SAMPLE

Recipes of 67 home-prepared diets promoted for use in dogs (n = 39 recipes) and cats (28) with CKD.

PROCEDURES

Recipes were analyzed with computer software to determine calories, macronutrient calorie distribution, and micronutrient concentrations and were assessed for appropriateness for the management of CKD.

RESULTS

Assumptions were required for the analysis of every recipe, and no recipe met all National Research Council nutrient recommended allowances (RA) for adult animals. Compared with RAs, concentrations of crude protein or at least 1 amino acid were low in 30 of 39 (76.9%) canine recipes and 12 of 28 (42.9%) feline recipes. Choline was most commonly below the RA in both canine (37/39 [94.9%]) and feline (23/28 [82.1%]) recipes; selenium (34/39 [87.2%] canine and 9/28 [32.1 %] feline recipes), zinc (24/39 [61.5%] canine and 19/28 [67.9%] feline recipes), and calcium (22/39 [56.4%] canine and 7/28 [25.0%] feline recipes) concentrations were also frequently below recommendations. The median phosphorus concentration in canine and feline recipes was 0.58 and 0.69 g/1,000 kcal, respectively.

CONCLUSIONS AND CLINICAL RELEVANCE

Many problems with nutritional adequacy were detected, and use of the recipes could result in highly variable and often inappropriate diets. Many recipes would not meet nutritional and clinical needs of individual patients and should be used cautiously for long-term feeding.

Domestic cats convert [2H8]-β-carotene to [2H4]-retinol following a single oral dose

Many animals convert β-carotene to retinol to meet their vitamin A (VA) requirement. However, this pathway is inefficient in many carnivores. This study quantified the plasma response to a single oral dose of [(2) H(8)]-β-carotene in adult domestic cats, including measurement of [(2) H(4)]-retinol derived from the dose. Cats were fed with either a control diet containing adequate VA (n = 5) or a VA-devoid diet (n = 5) for 28 days. An oral dose of either 5 mg/kg body weight (BW) (n = 4) or 10 mg/kg BW (n = 6) of [(2) H(8) ]-β-carotene was administered on day 28. Plasma samples were collected prior to dosing and at 6, 12, 24, 32, 48, 72, 120, 168 and 216 h post-dose. Plasma retinoids and β-carotene were measured using HPLC and [(2) H(4)]-retinol by GC-ECNCI-MS (gas chromatography/electron capture negative chemical ionization/mass spectrometry). β-carotene was undetectable in plasma prior to dosing. Post-dose, mean peak plasma β-carotene was 0.37 ± 0.06 nmol/ml at 9.0 ± 1.8 h following the dose, while [(2) H(4) ]-retinol peaked at 3.71 ± 0.69 pmol/ml at 55.2 ± 16.3 h. The ratio per cent of total area under the curve for [(2) H(4)]-retinol compared with the β-carotene response was 4.6 ± 2.6%. There was little effect of diet or dose on the β-carotene or [(2) H(4)]-retinol responses. The appearance of [(2) H(4)]-retinol in plasma indicates that cats are capable of converting β-carotene to active VA. Conversion efficiency was not calculated in this study, but it is likely inadequate to meet cats' VA requirement without the inclusion of preformed VA in the diet.

Abstract 4848: Pegylated arginine deiminase induces autophagy in canine melanoma and canine osteosarcoma

Arginine is a nonessential amino acid in adult mice, men and dogs, which undergoes both synthesis and degradation in complex series of compartmentalized steps at the cellular and systemic level. The urea cycle enzymes are responsible for this axis and is dependent on the levels of are argininosuccinate synthetase (ASS1) and argininosuccinate lyase (ASL). It has been shown that many human tumor types are auxotrophic for L-arginine typically due to very low or no specific activities of ASS1 and/or ASL and are thus sensitive to induction of cell death as a result of the depravation of this single nutrient. Pegylated arginine-deiminase (PEGADI) is a molecule with this mechanism of action and has entered phase I and II clinical trials in humans where it has proven its clinical utility in the treatment of hepatocellular carcinoma and melanoma.

The cancer-bearing dog serves an excellent spontaneous out-bred immune competent large animal model for numerous homologous neoplastic diseases in humans. The purpose of this study is to determine the status of arginine-synthetic enzymes and then evaluate the action of PEGADI in cultured canine cancer melanoma (12, 23, 36) and osteosarcoma (D17, 48-4, 29) cell lines. Using western blot analysis we found that each of these six canine cell lines expressed ASS1 and ASL. PEGADI depleted arginine in a time- and concentration-dependent manner in the cultured canine melanoma and osteosarcoma as measured by HPLC. Furthermore, the canine melanoma and osteosarcoma cells were very sensitive to this depletion. In particular, there was a dramatic loss of clonogenic survival in these cells treated with PEGADI (IC50 range: 0.03 uM at 96 h to 0.3 at 24 h). This sensitivity was apparently due to caspase independent cell killing as caspase 3, 8, or 9 were not activated. Changes in cell cycle distribution were quantitated with flow cytometry. Despite the lack of caspase activation, there was an increase in the number of cells in the Sub G1 population. To determine if PEGADI induced autophagy in these cells the conversion of microtubule-associated protein 1 light chain 3B (LC3B)-I to its lipidated form LC3B-II was assessed and showed there was a dose dependent induction of LC3B-II. Consistent with the induction of autophagy, results demonstrate an induction in the formation autophagolysosomes as determined by flow cytometery analysis of acridine orange staining of acidic vesicles, as well as fluorescent microscopy of treated cells stained with monodansylcadaverine. Our results support the notion that PEGADI may have clinical utility in the management of canine neoplasia. A clinical trial for this species is planned.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4848.

Plasma amino acid and whole blood taurine concentrations in cats eating commercially prepared diets

OBJECTIVE

To establish comprehensive reference ranges for plasma amino acid and whole blood taurine concentrations in healthy adult cats eating commercial diets and to evaluate the relationships of age, sex, body weight, body condition score (BCS), dietary protein concentration, and dietary ingredients with plasma amino acid and whole blood taurine concentrations.

ANIMALS

120 healthy adult cats.

PROCEDURES

Blood samples and a complete health and diet history were obtained for each cat, and reference intervals for plasma amino acid and whole blood taurine concentrations were determined. Results were analyzed for associations of age, breed, sex, body weight, BCS, use of heparin, sample hemolysis and lipemia, dietary protein concentrations, and dietary ingredients with amino acid concentrations.

RESULTS

95% reference intervals were determined for plasma amino acid and whole blood taurine concentrations. A significant difference in amino acid concentrations on the basis of sex was apparent for multiple amino acids. There was no clear relationship between age, BCS, body weight, and dietary protein concentration and amino acid concentrations. Differences in amino acid concentrations were detected for various dietary ingredients, but the relationships were difficult to interpret.

CONCLUSIONS AND CLINICAL RELEVANCE

This study provided data on plasma amino acid and whole blood taurine concentrations for a large population of adult cats eating commercial diets. Plasma amino acid and whole blood taurine concentrations were not affected by age, BCS, or body weight but were affected by sex and neuter status. Dietary protein concentration and dietary ingredients were not directly associated with plasma amino acid or whole blood taurine concentrations.

Effects of dietary lysine supplementation on upper respiratory and ocular disease and detection of infectious organisms in cats within an animal shelter

OBJECTIVE

To determine within a cat shelter effects of dietary lysine supplementation on nasal and ocular disease and detection of nucleic acids of Chlamydophila felis, feline calicivirus (FCV), and feline herpesvirus (FHV-1).

ANIMALS

261 adult cats.

PROCEDURES

Cats were fed a diet containing 1.7% (basal diet; control cats) or 5.7% (supplemented diet; treated cats) lysine for 4 weeks. Plasma concentrations of lysine and arginine were assessed at the beginning (baseline) and end of the study. Three times a week, cats were assigned a clinical score based on evidence of nasal and ocular disease. Conjunctival and oropharyngeal swab specimens were tested for FHV-1, FCV, and C felis nucleic acids once a week.

RESULTS

Data were collected from 123, 74, 59, and 47 cats during study weeks 1, 2, 3, and 4, respectively. By study end, plasma lysine concentration in treated cats was greater than that in control cats and had increased from baseline. There was no difference between dietary groups in the proportion of cats developing mild disease. However, more treated cats than control cats developed moderate to severe disease during week 4. During week 2, FHV-1 DNA was detected more commonly in swab specimens from treated versus control cats.

CONCLUSIONS AND CLINICAL RELEVANCE

Dietary lysine supplementation in the amount used in our study was not a successful means of controlling infectious upper respiratory disease within a cat shelter. Rather, it led to increases in disease severity and the incidence of detection of FHV-1 DNA in oropharyngeal or conjunctival mucosal swab specimens at certain time points.