Long-term biological variability and the generation of a new reference interval for plasma N-terminal pro-B-type natriuretic peptide in Labrador retrievers

Effects of a 28-day feeding trial of grain-containing versus pulse-based diets on cardiac function, taurine levels and digestibility in domestic dogs

In 2018, the US Food and Drug Administration reported a link between canine dilated cardiomyopathy (DCM) and grain-free diets. Evidence to support a link has emerged, but the specific ingredients responsible and the role of taurine or other causative factors remain unclear. We hypothesized dogs fed pulse-based, grain-free diets for 28 days will show decreased macronutrient digestibility, increased fecal bile acid excretion, and reduced plasma cystine, cysteine, methionine and taurine, causing sub-clinical cardiac or blood changes indicative of early DCM. Three diets were formulated using white rice flour (grain), whole lentil (grain-free), or wrinkled pea (grain-free) and compared to the pre-trial phase on a commercial grain-based diet. After 28 days of feeding each diet, the wrinkled pea diet impaired stroke volume and cardiac output, increased end-systolic ventricular diameter and increased plasma N-Terminal Pro-B-type Natriuretic Peptide (NT-ProBNP), albeit in a sub-clinical manner. Digestibility of some macronutrients and sulphur-containing amino acids, excluding taurine, also decreased with pulse-based compared to grain-based diets, likely due to higher fiber levels. Plasma taurine levels were unchanged; however, plasma methionine was significantly lower after feeding all test diets compared to the commercial diet. Overall, DCM-like changes observed with the wrinkled pea diet, but not lentil diet, after only 4 weeks in a breed not known to be susceptible support a link between pea-based diets and canine nutritionally-mediated DCM.

The Pulse of It: Dietary Inclusion of Up to 45% Whole Pulse Ingredients with Chicken Meal and Pea Starch in a Complete and Balanced Diet Does Not Affect Cardiac Function, Fasted Sulfur Amino Acid Status, or Other Gross Measures of Health in Adult Dogs

BACKGROUND

Pulses are an attractive alternative protein source for all mammals; however, recent reports suggest that these ingredients may be related to developing dilated cardiomyopathy in dogs.

OBJECTIVES

The primary objective of this study was to quantify the effects of dietary pulse intake by adult dogs on cardiac function using echocardiographic measurements and cardiac biomarkers N-terminal pro-B-type natriuretic peptide and cardiac troponin I (cTnI). Second, to investigate the effects of pulse consumption on plasma sulfur amino acid (SAA) concentrations as pulses are generally low in SAA and may limit taurine synthesis. Last, to assess the general safety and efficacy of feeding pulse-containing diets on canine body composition and hematological and biochemical indices.

METHODS

Twenty-eight privately-owned domestic Siberian Huskies (13 females; 4 intact, and 15 males; 6 intact) with a mean age of 5.3 ± 2.8 y (± SD) were randomly assigned to 1 of 4 dietary treatments (n = 7/treatment), with equal micronutrient supplementation and increasing whole pulse ingredient inclusion (0%, 15%, 30%, and 45%) with pea starch used to balance protein and energy.

RESULTS

After 20 wks of feeding, there were no differences (P > 0.05) in echocardiographic parameters, N-terminal pro-B-type natriuretic peptide, and cTnI concentrations among treatments or across time within treatment (P > 0.05), indicating no differences in cardiac function among treatments. Concentrations of cTnI remained below the safe upper limit of 0.2 ng/mL for all dogs. Plasma SAA status, body composition, and hematological and biochemical indices were similar among treatments and over time (P > 0.05).

CONCLUSIONS

The results from this study suggest that increasing the inclusion of pulses up to 45% with the removal of grains and equal micronutrient supplementation does not impact cardiac function concurrent with dilated cardiomyopathy, body composition, or SAA status and is safe for healthy adult dogs to consume when fed for 20 wks.

Responses in randomised groups of healthy, adult Labrador retrievers fed grain-free diets with high legume inclusion for 30 days display commonalities with dogs with suspected dilated cardiomyopathy

Early responses in healthy adult dogs fed grain-free diets with high inclusion of split peas (20%) and lentils (40%) that may lead to canine diet-induced dilated cardiomyopathy (DCM) were investigated. To help understand the clinical relevance of the findings, a survey of electronic health records (EHR) was conducted of dogs with and without suspected DCM for comparison. Control and Test diets were fed to Labrador retriever dogs for 30 days (n = 5 and 6, respectively). Blood and urine samples collected at baseline and days 3, 14 and 28/30 were analyzed for hematology, clinical biochemistry and taurine concentrations. The EHRs of dogs at Banfield® Pet Hospitals in the 2-year period 2018-2019 were surveyed, revealing 420 dogs diagnosed with DCM, which were compared with 420 breed, gender and age-matched healthy control dogs. Compared to baseline values, feeding the Test diet for 28 days caused progressive, significant (p < 0.001) decreases in red blood cell counts (RBC), hematocrit and total hemoglobin by 7.7, 8.3 and 6.3%, respectively, and a 41.8% increase in plasma inorganic phosphate. Commonalities in these parameters were observed in clinical DCM cases. Regarding taurine status, Test dogs transiently increased whole-blood (23.4%) and plasma (47.7%) concentrations on day 14, while taurine:creatinine ratio in fresh urine and taurine in pooled urine were reduced by 77 and 78%, respectively, on day 28/30. Thus grain-free, legume-rich Test diets caused reduced RBC and hyperphosphatemia, findings also indicated in dogs with suspected DCM. Changes in taurine metabolism were indicated. The data will aid in generating hypotheses for future studies.