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.

Background Dietary protein and phosphorus (P) restriction is the mainstay for nutritional management of chronic kidney disease (CKD). However, adequate restriction levels for cats with early CKD remain unclear. Objectives To investigate responses in cats with early CKD to varying dietary protein, P, and calcium (Ca) : P ratio. Animals Nineteen research colony cats with International Renal Interest Society stages 1-2 CKD. Methods In an opportunistic longitudinal case study, cats were fed a low protein (59 g/Mcal), low P (0.84 g/Mcal) dry diet (LP-LP; Ca : P = 1.9) for 18 months and later transitioned onto a moderate protein (76-98 g/Mcal), moderate P (1.4-1.6 g/Mcal) dry-wet diet regimen (MP-MP; Ca : P = 1.4-1.6) for 22 months. Fold-changes in serum creatinine, total Ca (tCa) and P (primary outcomes) and fibroblast growth factor 23 (FGF23) were assessed by linear-mixed models. Results While feeding LP-LP, mean serum creatinine decreased (0.87-fold, 95% confidence interval [CI] 0.81, 0.93, P < .001) to within reference range after 6 months, while increases in total Ca (tCa; 1.16-fold, 95% CI 1.11, 1.22, P < .001) and FGF23 (2.72-fold, 95% CI 1.72, 4.31, P < .001), but not in P (1.03-fold, 95% CI 0.945, 1.124, P = .94), were observed after 17 months. On MP-MP, mean creatinine, tCa and P remained within reference ranges and did not significantly change (P = .11, P = .98, and P = 1, respectively), while FGF23 significantly decreased (0.58-fold, 95% CI 0.36, 0.95, P = .02) after 22 months. Conclusions and Clinical Importance Cats with early CKD developed hypercalcemia after long-term feeding of a highly P-restricted diet. Increasing dietary P and reducing Ca : P ratio maintained renal markers, while improving Ca-P balance. Cats with early CKD could benefit from moderately protein- and P-restricted diets.

Age-related changes in gastrointestinal function have been reported in companion animals, but the impact on digestive efficiency remains uncertain. Healthy dogs (n = 37; 2.6–14.2 years) received four diets varying in total dietary fibre (TDF; 6–29%, as fed). Healthy cats (n = 28; 1–13 years) received four diets with two fat (10–12%; 17–18%) and TDF (9 and 12%) levels. In a crossover design, diets were provided over four consecutive 10-day cycles, including a 4-day faecal collection. Apparent crude protein (CP), ether extract (EE), TDF, calcium (Ca), and phosphorus (P) digestibilities were determined. The effect of age was analysed as a continuous variable in dogs and as differences between adult (1–5 years) and senior (7–13 years) cats. In dogs, EE digestibility was unaffected by age (p > 0.10). Dogs of 6–12 years had higher digestibility of CP (p = 0.032), TDF (p = 0.019), Ca (p = 0.019), and P (p = 0.024) when fed the 6% TDF diet. Senior cats had greater digestibility of TDF (p < 0.01) and Ca (p = 0.024) but had lower EE and CP digestibility with one diet (17% fat; 9%TDF) (age, p > 0.10; diet × age, p < 0.001). Healthy ageing was associated with preserved nutrient digestibility in dogs and cats within the age ranges studied. The effect of ingredient sources in senior cats warrants further investigation.

Phosphorus (P) is an essential nutrient; however, potential health impacts of high dietary levels of added soluble, highly bioavailable P salts especially are a concern. P sources with lower bioavailability are considered safer. Yet, speciation of different P sources to assess diets’ risk to health is challenging. This investigation tested the value of in vitro water extraction and digestion assays to predict in vivo P apparent bioavailability/digestibility in feline diets. Thirty wet (n = 18) and dry (n = 12) format experimental and commercial cat foods were analyzed for nutrient content. Triplicate samples were subjected to in vitro water extraction, single-phase acidic (gastric; G) digestion, and dual-phase gastric and small intestinal (G-SI) digestion assays. Soluble and insoluble P were determined in the supernatant and pellet, respectively. A subset of the diets (seven wet, nine dry diets) was fed to healthy, adult cats (n = 7–24) to determine in vivo apparent P digestibility. Information on the soluble P salt sources and their contribution to total dietary P was available for some diets. Associations between data from the different in vitro assays and in vivo digestibility trials and the influence of different diet parameters were obtained using Pearson correlation and linear regression modeling. The % soluble P obtained from G-SI digestion assay correlated well with in vivo apparent P digestibility for wet (Pearson coefficient 0.926, p = 0.003), but not for dry diets (Pearson coefficient −0.074, p = 0.849). In contrast, the % soluble P determined by water extraction correlated well with the % soluble P salt contribution to total P for dry (Pearson coefficient 0.901, p < 0.001), but not for wet diets (Pearson coefficient −0.407, p = 0.365). Thus, 20 min water extraction can be used to predict soluble P salt content in dry diets; however, differing Ca:P ratios and water solubility of the P sources may affect the outcome and false-positive results can occur. The G-SI digestion assay employed can also be used to predict in vivo P digestibility. However, again, diet format, Ca:P ratios in diets, and possibly other factors can impact the results. Thus, data from in vitro assays to assess P sources and bioavailability need to be interpreted with care.

The implications of long-term high calcium (Ca) intake are well documented in growing dogs and in adult dogs of large breed size, however, the consequences on other breeds and breed sizes are yet to be determined. Eighteen neutered adult beagles, nine males and nine females aged 1.4–4.4 years, were randomized to control or test diets providing in g∙4184 kJ⁻¹ (1000 kcal⁻¹): 1.44 and 7.19 total Ca balanced with 1.05 and 4.25 total phosphorus, respectively, for 40 weeks. Health parameters, ultrasound scans, radiographs, glomerular filtration rate, and mineral balance were measured at eight-week intervals. All dogs remained healthy with no measured evidence of orthopedic, urinary, or renal disease. The test diet resulted in a 5.2 fold increase in fecal Ca excretion. Apparent Ca digestibility (%) and Ca balance (g/d) did not significantly (p > 0.05) change from baseline in the test diet group, although dogs displayed a positive Ca balance (maximum at week 8, 1.11 g/d with 95% CI (0.41, 1.80)) before a neutral Ca balance was restored at week 32. Despite an initial positive Ca balance, we can conclude that no measurable adverse health effects were observed as a result of the test diet fed in this study in beagles over a period of 40 weeks.