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

Abstract

BackgroundTaurine 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.ObjectiveWe 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.MethodsAdult, 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.ResultsWhen 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.ConclusionsBlood 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.

Pit bull–type breeds with dilated cardiomyopathy eating nontraditional diets improve after diet change (2015–2022)

“…The fact that none of the dogs measured had taurine deficiency argues against taurine deficiency playing a primary role in the current episode of diet-associated DCM, but further investigation is needed given the limited percentage of dogs in this study in which taurine was evaluated. In addition, a recent study 22 showed that whole blood taurine concentrations (and, in some dogs, plasma concentrations) may not be a sensitive measure of skeletal muscle depletion, and other measures of taurine status may be needed.…”

“…Most cases (n = 84) were from the US, with 18 states represented; cases were also submitted from Canada (6) and Germany (1). All DCM cases were diagnosed between January 2015 and August 31, 2022, as follows: 2015 (n = 1), 2016 (0), 2017 (2), 2018 (10), 2019 (22), 2020 (20), 2021 (21), and 2022 (through August 31; 15). At the time of DCM diagnosis, 76 dogs were eating commercial diets, 1 dog was eating a homemade diet, and diet was unknown or there was insufficient information available to determine whether the diet was nontraditional or traditional in 14 dogs (Figure 1).…”

Amino acid nutrition and metabolism in domestic cats and dogs

“…Most breeds of dogs can synthesize sufficient taurine when fed a methionine- and cysteine-adequate diet [ 43 ]. However, an inadequate intake of methionine and cysteine in diets [e.g., plant (e.g., peas, lentils, and rice)-based foods with no or insufficient taurine] may contribute to the development of dilated cardiomyopathy characterized by thin heart muscle and enlarged chambers in some breeds of dogs [ 98 , 99 ]. For example, a small proportion (1.3%–2.5%) of Newfoundland dogs fed commercially available diets that were considered to be complete and balanced in nutrition have a deficiency of taurine [ 100 ] due to reduced taurine synthesis possibly as a result of gene mutations [ 101 ].…”

“…Only in the breeds of dogs that possess sufficient enzymes for taurine synthesis can the adequate provision of methionine plus cysteine in their diets prevent metabolic diseases such as dilated cardiomyopathy. Although concentrations of taurine in plasma and skeletal muscle reflect its availability in these animals, those in the whole blood may not be a sensitive indictor of taurine depletion caused by a low intake of bioavailable sulfur AAs in dogs, especially in large dogs [ 99 ].…”

“…Multiple factors should be considered in formulating diets, including endogenous AA synthesis, the digestibility and bioavailability of dietary nutrients, the presence of antinutritive factors in foodstuffs, the fermentability and quantity of dietary fiber, and interactions among food constituents [ 33 , 61 , 133 ]. Furthermore, requirements of cats and dogs for dietary AAs (including sulfur AAs) may critically depend on the catabolism of these nutrients by the intestinal microbiota [ 75 , 99 ].…”