Dietary protein source (soybean vs. casein) and taurine status affect kinetics of the enterohepatic circulation of taurocholic acid in cats

Plasma and Whole Blood Taurine Concentrations in Dogs May Not Be Sensitive Indicators of Taurine Deficiency When Dietary Sulfur Amino Acid Content Is Reduced

Background

Taurine status is impacted by dietary supply of methionine and cysteine (SAA) and possibly intestinal microbial activity, where plasma and whole blood taurine concentrations are currently used to evaluate taurine status.

Objective

We determined effects of dietary SAA restriction on rate and extent of taurine depletion of blood and skeletal muscle in dogs of two body sizes, and whether oral antibiotic administration affected the taurine depletion and fecal bile acid excretion of the dogs.

Methods

Adult, male, Beagles (n = 6; 10.1–13.1 kg) and larger mixed-breed dogs (n = 6; 28.5–41.1 kg) were given four dry-expanded diets, whereby each successive diet contained lower protein and/or SAA concentration. After receiving the final diet for 44 weeks, all dogs were orally administered a mixture of ampicillin, neomycin sulfate, and metronidazole for 12 weeks. Taurine concentrations were determined every 2–4 weeks in venous blood and voided urine and every 4 to 16 weeks in biopsied semimembranosus muscle. Fecal bile acid excretion before and after antibiotics administration were quantified.

Results

When given for 36 weeks the lowest SAA diet, 3.4% methionine and 2.9% cystine, taurine concentrations in whole blood were not different between groups, while taurine in plasma declined (P < 0.05) in large but not in small dogs, and taurine in biopsied muscle decreased (P < 0.05) by 50% in large and by 37% in small dogs. Concentrations of taurine in muscle were lower (P < 0.01) and fecal bile acids greater (P = 0.001) in large than small dogs. Antibiotic administration restored plasma and muscle taurine to initial concentrations and halved fecal bile acid excretion by dogs of both groups.

Conclusions

Blood taurine concentration may not be a sensitive indictor of taurine depletion caused by low intake of bioavailable SAA in dogs, especially in large dogs. Taurine status and dietary SAA requirements of dogs may substantively depend on taurine loss mediated by intestinal microbiota.

Examining the Effects of Diet Composition, Soluble Fiber, and Species on Total Fecal Excretion of Bile Acids: A Meta-Analysis

Bile acids (BA) are produced in the liver and conjugated with glycine or taurine before being released into the small intestine to aid with lipid digestion. However, excessive BA losses through feces can occur due to several dietary factors that in turn require greater production of BA by the liver due to a reduction in BA recycling. Consequently, net utilization of taurine and/or glycine is increased. To quantify this impact, we conducted a meta-analysis to investigate the effect of soluble fiber, diet composition, and species on fecal excretion of BA. After a systematic review of the literature, twelve studies met all inclusion criteria. Dietary carbohydrate, protein, fat, cellulose, cholesterol, soluble fiber and animal species were tested as independent variables. Mixed models were developed treating study as a random effect, and fixed effect variables were retained at P < 0.05 significance and where collinearity was absent between multiple X variables. A total of ten studies comprised of four species [(rat = 5), hamster (n = 1), guinea pig (n = 3) and dog (n = 1)], and 30 observations were evaluated in the final models after outlier removal. Model evaluation was based on the corrected Akaike Information Criteria, the concordance correlation coefficient and the root mean square prediction error. Three base models were developed, examining carbohydrate, protein and fat impacts separately. The best fitting models included the fixed effect of species and the interaction between soluble fiber (yes/no) and dietary carbohydrate, protein or fat (%, as-fed). Increased concentrations of dietary protein and fat resulted in greater fecal excretion of BA (P < 0.05). Conversely, increasing levels of dietary carbohydrate led to lower excretions of BA (P < 0.05). Increased dietary soluble fiber containing ingredients resulted in greater excretion of BA in all models (P < 0.05). Rats had greater excretion of BA compared to hamsters and guinea pigs (P < 0.05) in all models, and also compared to dogs (P < 0.05) in the carbohydrate model. The findings from this meta-analysis indicate that not only soluble fiber, but also increasing levels of dietary fat and protein may result in greater fecal excretion of BA, potentially altering taurine and/or glycine metabolism and affecting the need for diet delivery of these AA.

Low plasma taurine levels in English cocker spaniels diagnosed with dilated cardiomyopathy

OBJECTIVES

The aims of this study were to evaluate taurine levels in English cocker spaniels with dilated cardiomyopathy and assess their survival time and natural progression of their disease.

MATERIALS AND METHODS

Retrospective comparison of English cocker spaniels with dilated cardiomyopathy phenotype with and without taurine deficiency at the cardiology department of a UK academic referral centre between 2008 and 2018.

RESULTS

Taurine plasma concentration was available in 16 English cocker spaniels with dilated cardiomyopathy phenotype; 13 of 16 had congestive heart failure and three of 16 did not. Taurine concentration was low (<50 μmol/L) in 13 of 16 and normal in three of 16. Deficient dogs received taurine supplementation in addition to conventional cardiac medications. Eight dogs were still alive at the end of this study and eight were dead. MST for all dogs included in the study was 2800 days. Left ventricular systolic function improved and left ventricular dimensions reduced in English cocker spaniels with taurine deficiency following taurine supplementation and conventional cardiac therapy, although similar results were observed in English cocker spaniels with normal taurine concentration on cardiac therapy alone.

CLINICAL SIGNIFICANCE

Based on laboratory reference intervals, low taurine concentrations were common in English cocker spaniels with dilated cardiomyopathy, showing a possible association between dilated cardiomyopathy in English cocker spaniels and taurine deficiency; supplementation with taurine was not curative.

Provision of High Meat Content Food and Object Play Reduce Predation of Wild Animals by Domestic Cats Felis catus

Predation by domestic cats Felis catus can be a threat to biodiversity conservation,^1-3 but its mitigation is controversial.⁴ Confinement and collar-mounted devices can impede cat hunting success and reduce numbers of animals killed,⁵ but some owners do not wish to inhibit what they see as natural behavior, perceive safety risks associated with collars, or are concerned about device loss and ineffectiveness.^6,7 In a controlled and replicated trial, we tested novel, non-invasive interventions that aim to make positive contributions to cat husbandry, alongside existing devices that impede hunting. Households where a high meat protein, grain-free food was provided, and households where 5-10 min of daily object play was introduced, recorded decreases of 36% and 25%, respectively, in numbers of animals captured and brought home by cats, relative to controls and the pre-treatment period. Introduction of puzzle feeders increased numbers by 33%. Fitting Birdsbesafe collar covers reduced the numbers of birds captured and brought home by 42% but had no discernible effect on mammals. Cat bells had no discernible effect. Reductions in predation can be made by non-invasive, positive contributions to cat nutrition and behavior that reduce their tendency to hunt, rather than impede their hunting. These measures are likely to find support among cat owners who are concerned about the welfare implications of other interventions.

A commercial grain-free diet does not decrease plasma amino acids and taurine status but increases bile acid excretion when fed to Labrador Retrievers

Grain-free diets tend to have greater inclusions of pulses in contrast to grain-based diets. In 2018, the Food and Drug Administration (FDA) released a statement that grain-free diets may be related to the development of canine dilated cardiomyopathy (DCM). However, all dog foods met regulatory minimums for nutrient inclusion recommended by the Association of American Feed Controls Official. In some FDA case reports, but not all, dogs diagnosed with DCM also had low concentrations of plasma or whole blood taurine; thus, we hypothesized that feeding these diets will result in reduced taurine status from baseline measures. The objective of this study was to determine the effects of feeding a grain-free diet to large-breed dogs on taurine status and overall health. Eight Labrador Retrievers (four males and four females; Four Rivers Kennel, MO) were individually housed and fed a commercial complete and balanced grain-free diet (Acana Pork and Squash formula; APS) for 26 wk. Fasted blood samples were collected prior to the start of the trial (baseline; week 0) and at weeks 13 and 26 for analyses of blood chemistry, hematology, plasma amino acids, and whole blood taurine. Urine was collected by free catch at weeks 0 and 26 for taurine and creatinine analyses. Fresh fecal samples were collected at weeks 0 and 26 for bile acid analyses. Data were analyzed using the GLIMMIX procedure with repeated measures in SAS (v. 9.4). Plasma His, Met, Trp, and taurine and whole blood taurine concentrations increased over the course of the study (P < 0.05). Urinary taurine to creatinine ratio was not affected by diet (P > 0.05). Fecal bile acid excretion increased after 26 wk of feeding APS to dogs. Despite the higher fecal excretion of bile acids, plasma and whole blood taurine increased over the 26-wk feeding study. These data suggest that feeding APS, a grain-free diet, over a 26-wk period improved taurine status in Labrador Retrievers and is not the basis for the incidence of DCM for dogs fed APS. Other factors that may contribute to the etiology of DCM should be explored.

Effects of different carbohydrate sources on taurine status in healthy Beagle dogs

This study evaluated the effects of a grain-based (GB) and grain-free (GF) diet on protein utilization and taurine status in healthy Beagle dogs. Two practical dog diets sufficient in crude protein, sulfur amino acids, and taurine content were formulated with the same ingredients with exception of the carbohydrate sources. The GB contained sorghum, millet, and spelt while potatoes, peas, and tapioca starch were used in the GF. A total of 12 Beagle dogs were used in a completely randomized design with six replicates per treatment. The study consisted of an adaptation period of 2 wk followed by an experimental period of 28 d in which GB and GF were fed to the dogs. At the end of the adaptation period and every 2 wk after it (day 0, day 14, day 28), markers of taurine metabolism were analyzed in whole blood (taurine), plasma (taurine, methionine, and cystine), urine (taurine:creatinine), and fresh fecal samples (primary and secondary bile acids). Fecal samples were collected during the last 6 d of experimental period for digestibly assessment using titanium dioxide as an external marker. Taurine markers and digestibility data were analyzed in a repeated measures model and one-way ANOVA, respectively, using PROC GLIMMIX in SAS (version 9.4). Apparent crude protein digestibility was not affected by treatment, but dogs fed GF diet had lower apparent organic matter digestibility compared with those fed GB (P < 0.05). Greater plasma taurine concentrations were observed at days 14 and 28 compared with day 0; wherein dogs fed GF exhibited greater increase compared to those fed GB (P < 0.05). Whole blood taurine concentrations, plasma methionine concentrations, and urinary taurine:creatinine were also greater at days 14 and 28 compared with day 0 (P < 0.05), but no effect of diet was observed. Total bile acid excretion was similar between GF and GB groups, but dogs fed GF excreted a higher proportion of primary bile acids compared with those fed GB (25.49% vs. 12.09% at day 28, respectively). In summary, overall taurine status was not affected by dietary treatments, however, our results suggest that the higher content of oligosaccharides and soluble fibers in the GF diet may alter the composition of the fecal bile acid pool.

Nutritional inadequacies in commercial vegan foods for dogs and cats

The objective of this study was to evaluate the macronutrients composition, fatty acid and amino acid profiles, and essential minerals content of all vegan foods for dogs and cats available in the Brazilian market, and to compare results with FEDIAF (2019) and AAFCO (2019) recommendations. Four vegan pet foods were assessed (three for dogs and one for cats). The comparisons were made in a descriptive manner. All foods met the minimum recommendations for macronutrients. Arachidonic acid was not reported in any food label. Regarding the FEDIAF recommendations, one food for dogs had low calcium, another had low potassium and a third had low sodium. The cat food presented potassium content lower than recommended. The Ca:P ratio did not meet the minimum recommendation of FEDIAF (2019) and AAFCO (2019) in any of the dog’s foods analyzed, and the cat food also did not present the minimum recommendation based on FEDIAF (2019). Copper concentrations exceeded the legal limit in all foods. Zinc concentrations exceeded this limit in two foods (one for dogs and one for cats) and iron levels exceeded the legal limit in one dog food. One of the dog foods did not meet the minimum recommendation for methionine and the cat food did not meet the minimum recommendation for arginine. In addition, when the amount of nutrients consumed by animals with low energy requirements was simulated, in addition to the same non-conformities described above, it was observed that the cat food does not meet the minimum recommended of protein and taurine in unit/Kg^0.67. It was concluded that all foods analyzed had one or more nutrients below the recommended levels and some presented zinc and copper excess, therefore, these foods should not be recommended for dogs and cats, because dietary deficiencies found may lead to health risks for dogs and cats. Furthermore, manufacturers should review their formulations to ensure the nutritional adequacy of these foods.

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.

Cloning, tissue and ontogenetic expression of the taurine transporter in the flatfish Senegalese sole (Solea senegalensis)

Flatfish species seem to require dietary taurine for normal growth and development. Although dietary taurine supplementation has been recommended for flatfish, little is known about the mechanisms of taurine absorption in the digestive tract of flatfish throughout ontogeny. This study described the cloning and ontogenetic expression of the taurine transporter (TauT) in the flatfish Senegalese sole (Solea senegalensis). Results showed a high similarity between TauT in Senegalese sole and other vertebrates, but a change in TauT amino acid sequences indicates that taurine transport may differ between mammals and fish, reptiles or birds. Moreover, results showed that Senegalese sole metamorphosis is an important developmental trigger to promote taurine transport in larvae, especially in muscle tissues, which may be important for larval growth. Results also indicated that the capacity to uptake dietary taurine in the digestive tract is already established in larvae at the onset of metamorphosis. In Senegalese sole juveniles, TauT expression was highest in brain, heart and eye. These are organs where taurine is usually found in high concentrations and is believed to play important biological roles. In the digestive tract of juveniles, TauT was more expressed in stomach and hindgut, indicating that dietary taurine is quickly absorbed when digestion begins and taurine endogenously used for bile salt conjugation may be recycled at the posterior end of the digestive tract. Therefore, these results suggest an enterohepatic recycling pathway for taurine in Senegalese sole, a process that may be important for maintenance of the taurine body levels in flatfish species.

Idiosyncratic nutrient requirements of cats appear to be diet-induced evolutionary adaptations

Cats have obligatory requirements for dietary nutrients that are not essential for other mammals. The present review relates these idiosyncratic nutritional requirements to activities of enzymes involved in the metabolic pathways of these nutrients. The high protein requirement of cats is a consequence of the lack of regulation of the aminotransferases of dispensable N metabolism and of the urea cycle enzymes. The dietary requirements for taurine and arginine are consequences of low activities of two enzymes in the pathways of synthesis that have a negative multiplicative effect on the rate of synthesis. Cats have obligatory dietary requirements for vitamin D and niacin which are the result of high activities of enzymes that catabolise precursors of these vitamins to other compounds. The dietary requirement for pre-formed vitamin A appears to result from deletion of enzymes required for cleavage and oxidation of carotenoids. The n-3 polyunsaturated fatty acids (PUFA) requirements have not been defined but low activities of desaturase enzymes indicate that cats may have a dietary need for pre-formed PUFA in addition to those needed by other animals to maintain normal plasma concentrations. The nutrient requirements of domestic cats support the thesis that their idiosyncratic requirements arose from evolutionary pressures arising from a rigorous diet of animal tissue. These pressures may have favoured energy conservation through deletion of redundant enzymes and modification of enzyme activities to result in metabolites more suited to the cat's metabolism. However, this retrospective viewpoint allows only recognition of association rather than cause and effect.

Low plasma taurine concentration in Newfoundland dogs is associated with low plasma methionine and cyst(e)ine concentrations and low taurine synthesis

Although taurine is not dietarily essential for dogs, taurine deficiency and dilated cardiomyopathy (DCM) are sporadically reported in large-breed dogs. Taurine status and husbandry were examined in 216 privately owned Newfoundlands, a giant dog breed with high incidence of idiopathic DCM (1.3-2.5%). Plasma taurine concentration was positively correlated (P < 0.01) with plasma cyst(e)ine (r = 0.37) and methionine (r = 0.35) concentrations and was similar across age, sex, neutering status, body weight, and body-condition scores. Plasma taurine concentration was low (< or =40 micromol/L) in 8% of dogs. Dogs with low plasma taurine were older, less active, had more medical problems and treatments, and had lower plasma albumin, cyst(e)ine, tryptophan, and alpha-amino-n-butyric acid concentrations than the other dogs (P < 0.05). Of 9 taurine-deficient, clinically evaluated dogs, 3 had DCM that was reversed by taurine supplementation and 1 had retinal degeneration. When given a diet apparently adequate in sulfur amino acids (5.4 g/kg) for 3 wk, 6 Newfoundlands (52.5 +/- 2.3 kg, 3.5-7 y), compared with 6 Beagles (13.2 +/- 2.3 kg, 5.5 y), had lower (P < 0.01) concentrations of plasma taurine (49 +/- 16 vs. 97 +/- 25 micromol/L) and cyst(e)ine and blood glutathione, lower (P < 0.01) de novo taurine synthesis (59 +/- 15 vs. 124 +/- 27 mg x kg(-0.75) x d(-1)), and greater (P < 0.05) fecal bile acid excretion (1.7 +/- 0.2 vs. 1.4 +/- 0.2 micromol/g). Newfoundlands would appear to have a higher dietary sulfur amino acid requirement than Beagles, a model breed used in nutrient requirement determinations.

Traditional and nontraditional effective and noneffective therapies for cardiac disease in dogs and cats

In this article, I presented my (admittedly biased) perspective of the current state of knowledge addressing the role of traditional and non-traditional therapeutics. The focus has been on the nontraditional therapeutics. Among these, the only ones I currently consider to have any documented value are taurine and, less commonly, L-carnitine. The role of taurine (and likely carnitine) remains limited to cases of documented deficiency. In the case of cats with taurine deficiency-induced myocardial failure, it is now clear that most cases are the result of formulation errors by owners and manufacturers. In dogs, it is less clear if the causes of taurine deficiencies represent manifestations of pathologic conditions or dietary formulations errors. Increasingly, it seems the latter may prove to be the case in most, if not all, circumstances. Finally, I would like to reiterate the conclusions of the last time I addressed this topic (with coauthors Kittleson and Sanderson) in this publication. Remember that there is limited evidence to support the therapeutic recommendations you read or hear in most circumstances. The urge to do "something" for patients can be overwhelmingly attractive. Nevertheless, whether it is administration of drugs or prescribing nutraceuticals or prescription diets, strongly consider the source of the information urging you to prescribe, the strength of the evidence presented, the financial costs to the owner, and the potential risks and benefits to the patient.

Taurine deficiency in Newfoundlands fed commercially available complete and balanced diets

OBJECTIVE

To determine taurine status in a large group of Newfoundlands related by environment, diet, or breeding to a dog with dilated cardiomyopathy and taurine deficiency.

DESIGN

Prospective study.

ANIMALS

19 privately owned Newfoundlands between 5 months and 11.5 years old that had been fed commercial dry diets meeting established nutrient recommendations.

PROCEDURE

Diet histories were obtained, and blood, plasma, and urine taurine concentrations and plasma methionine and cysteine concentrations were measured. In 8 dogs, taurine concentrations were measured before and after supplementation with methionine for 30 days. Ophthalmic examinations were performed in 16 dogs; echocardiography was performed in 6 dogs that were taurine deficient.

RESULTS

Plasma taurine concentrations ranged from 3 to 228 nmol/mL. Twelve dogs had concentrations < 40 nmol/mL and were considered taurine deficient. For dogs with plasma concentrations < 40 nmol/mL, there was a significant linear correlation between plasma and blood taurine concentrations. For dogs with plasma concentrations > 40 nmol/mL, blood taurine concentrations did not vary substantially. Taurine-deficient dogs had been fed lamb meal and rice diets. Retinal degeneration, dilated cardiomyopathy, and cystinuria were not found in any dog examined for these conditions. The taurine deficiency was reversed by a change in diet or methionine supplementation.

CONCLUSIONS AND CLINICAL RELEVANCE

Results indicate a high prevalence of taurine deficiency among an environmentally and genetically related cohort of Newfoundlands fed apparently complete and balanced diets. Blood taurine concentrations indicative of taurine deficiency in Newfoundlands may be substantially less than concentrations indicative of a deficiency in cats.

Effects of dietary fat and L-carnitine on plasma and whole blood taurine concentrations and cardiac function in healthy dogs fed protein-restricted diets

OBJECTIVE

To evaluate plasma taurine concentrations (PTC), whole blood taurine concentrations (WBTC), and echocardiographic findings in dogs fed 1 of 3 protein-restricted diets that varied in fat and L-carnitine content.

ANIMALS

17 healthy Beagles.

DESIGN

Baseline PTC and WBTC were determined, and echocardiography was performed in all dogs consuming a maintenance diet. Dogs were then fed 1 of 3 protein-restricted diets for 48 months: a low-fat (LF) diet, a high-fat and L-carnitine supplemented (HF + C) diet, or a high-fat (HF) diet. All diets contained methionine and cystine concentrations at or above recommended Association of American Feed Control Officials (AAFCO) minimum requirements. Echocardiographic findings, PTC, and WBTC were evaluated every 6 months.

RESULTS

The PTC and WBTC were not significantly different among the 3 groups after 12 months. All groups had significant decreases in WBTC from baseline concentrations, and the HF group also had a significant decrease in PTC. One dog with PT and WBT deficiency developed dilated cardiomyopathy (DCM). Taurine supplementation resulted in significant improvement in cardiac function. Another dog with decreased WBTC developed changes compatible with early DCM.

CONCLUSIONS AND CLINICAL RELEVANCE

Results revealed that dogs fed protein-restricted diets can develop decreased taurine concentrations; therefore, protein-restricted diets should be supplemented with taurine. Dietary methionine and cystine concentrations at or above AAFCO recommended minimum requirements did not prevent decreased taurine concentrations. The possibility exists that AAFCO recommended minimum requirements are not adequate for dogs consuming protein-restricted diets. Our results also revealed that, similar to cats, dogs can develop DCM secondary to taurine deficiency, and taurine supplementation can result in substantial improvement in cardiac function.

High dietary protein and taurine increase cysteine desulfhydration in kittens

The objective of this study was to determine the effect of dietary protein and taurine on cysteine desulfhydration in various kitten tissues. Cysteine desulfhydration was assessed in liver, kidney, skeletal muscle, heart, spleen, brain and jejunum of kittens fed one of the following diets for 5 wk: 20% protein, 0% taurine diet (LP0T); 20% protein, 0.15% taurine diet (LPNT); 60% protein, 0% taurine diet (HP0T); and 60% protein, 0.15% taurine diet (HPNT). Cats fed LP0T and HP0T had been fed a taurine-free diet for 10 wk before the 5-wk experiment. The activity of cysteine desulfhydration was determined by measuring the production of H(2)(35)S from (35)S-cysteine in the presence and absence of alpha-ketoglutarate (alphaKG) in the incubation medium. Liver and kidney had the highest total activities among the tissues tested (P < 0.01). Total hepatic desulfhydration activities [micromol H(2)S/(min. kg body wt)] in cats fed LP0T, LPNT, HP0T and HPNT were (mean +/- SEM) 117 +/- 6, 135 +/- 10, 137 +/- 10 and 190 +/- 9, respectively. Dietary taurine had a significant effect on activity when expressed per gram liver (P < 0.01), per gram protein (P < 0.05) and per kilogram body weight (P < 0.001). Dietary protein had a significant effect (P < 0.001) only when activity was expressed relative to body weight because of the significant effect of protein on relative liver weight. The direct pathway via cysteine desulfhydrase appears to be the major route of cysteine desulfhydration in kitten liver because the values obtained in the absence of alphaKG were 81-88% of those obtained in the presence of alphaKG.

Nutritional support for dogs and cats with hepatobiliary disease

Nutritional intake in the patient with hepatobiliary disease provides the cornerstone of balanced medical care. Optimal recommendations require consideration of general nutritional principles, special species requirements and contemporary needs uniquely related to the patient's medical problem. Although general recommendations follow well-established guidelines developed to meet metabolic requirements for normal health, there is little information regarding altered requirements in animals that are ill. Consequently, recommendations for animals have been derived empirically from studies completed in humans, most work having been done in patients with end stage cirrhosis or liver failure complicated by hepatic encephalopathy. This is problematic because most veterinary patients with liver disease are not in hepatic failure and do not suffer from hepatic encephalopathy. Iatrogenic malnutrition can develop in patients when protein-restricted diets are inappropriately recommended. Insufficient energy intake and negative nitrogen balance can complicate a patient's condition, impairing tissue regeneration and recovery from disease. This paper reviews strategies that can be used to individualize nutritional management in small companion animals with hepatobiliary disease. Consideration is given to both the known and controversial issues regarding energy requirements, dietary energy distribution, vitamin and micronutrient supplementation, the special requirements of the cat with hepatic lipidosis, as well as strategies effective for palliation of hepatic encephalopathy.

Microbial degradation of taurine in fecal cultures from cats given commercial and purified diets

Freshly passed feces were collected from cats (n = 5-7) given cooked and uncooked commercial canned-type diets, casein and soy protein containing purified diets and a commercial extruded diet. The feces were anaerobically cultured in medium containing either taurine, taurocholic acid or [2-3H]taurine for 24 h at 37 degrees C. Taurine degradation in cultures was greatest for cultures from cats receiving diets reputed to cause taurine depletion. Diaminopimelic acid in feces indicated that differences in taurine degradation rate among groups was associated with differences in bacterial numbers in feces. After 6 h of incubation, < 10% of taurocholate and > 60% of taurine remained. Nearly all the tritium on the labeled taurine was recovered as water. These results indicate that deconjugation and deamination are the initial steps in microbial catabolism of taurocholic acid and that enteric microbial growth may be a major determinant of dietary taurine requirement of cats.