Objectives The aim of this report is to describe the identification of a novel vitamin D metabolite, a C-3, alpha-epimer of 25-hydroxycholecalciferol (3-epi-25(OH)D), in serum and plasma extracts of cat blood and compare its abundance in cat, dog and rat serum to 25-hydroxycholecalciferol (25(OH)D), a conventional marker of vitamin D status. Methods Serum 25(OH)D and 3-epi-25(OH)D concentrations were measured in healthy cohorts of cats (n = 8), dogs (n = 8) and rats (n = 17) using validated reverse and normal-phase high-performance liquid chromatography methods. The methods were verified using liquid chromatography tandem mass spectrophotometry. Dietary intake and dietary concentrations of vitamin D were also measured for evaluation of species differences and effect of dietary change on vitamin D metabolite concentrations. Differences between cat serum and plasma metabolite concentrations were determined. Results Detectable concentrations of 3-epi-25(OH)D were observed in all cats and rats. No 3-epi-25(OH)D was detected in dogs, where our limit of detection was 5 ng/ml. There were significant differences ( P <0.05) in serum concentrations of 25(OH)D and 3-epi-25(OH)D among species, with cats having the greatest concentrations of both metabolites. Serum and plasma results were not significantly different. A diet change, which resulted in an increase in vitamin D intake among the cats, affected serum concentration with an increase ( P = 0.004) in 3-epi-25(OH)D but no significant change in 25(OH)D. Conclusions and relevance Serum and plasma of cats contain 3-epi-25(OH)D in varied and extraordinary concentrations, much greater than in rats and certainly than that of dogs, a species for which the metabolite was not detected. Importantly, this finding indicates a C-3 epimerization pathway is quantitatively significant for vitamin D metabolism in domestic cats, making 3-epi-25(OH)D assays essential for the evaluation of vitamin D status in cats and positioning the cat as a novel model for study of this pathway.

A 10-year old, castrated male, Bichon Frise with a history of hyperadrenocorticism and intrahepatic portal vein hypoplasia was diagnosed with superficial necrolytic dermatitis (SND). The dog exhibited thick crusts on the chin, muzzle, prepuce, and paws. In addition, the dorsal surfaces of all paws were erythematous while the palmar/plantar surfaces were hyperkeratotic, hardened, and painful. The dog was treated with intravenous amino acid infusions (AAI), raw egg yolks, as well as zinc and omega-3 fatty acid oral supplements. The dog required AAI once every 2-3 weeks because this coincided with recrudescence of painful skin lesions. The dog was subsequently diagnosed with diabetes mellitus. A consult with the Nutrition Service was pursued 220 days after the original SND diagnosis because of concern for feeding raw eggs and for malnutrition since appetite was variable, muscle condition was reduced, and greater than 50% of ingested calories were from foods that were not nutritionally complete. There was also concern regarding the variability of the diet and the impact it would have on the management of diabetes mellitus. The diet was prepared by the dog owner according to a provided recipe and presented twice daily. The diet was rich in high quality protein and fat. All other treatments including medications, supplements, and bathing schedule remained unchanged at the time of diet modification. The dog was subclinical for SND associated clinical signs approximately 3 weeks after the diet modification, which also coincided with the last AAI. The AAI was postponed and was next administered 7 weeks later (i.e., 10 weeks from the previous infusion). The dog remained subclinical for SND related clinical signs and continued to receive AAI once every 10-12 weeks until he was euthanized 718 days later for complications related to severe multi-drug resistant, skin infections. In conclusion, this report highlights a novel role for nutritionally balanced home-made diets designed by a board-certified veterinary nutritionist could substantially increase time interval between AAI and outcome in dogs with SND.

Background Body surface area (BSA) can reflect metabolic rate that might normalize dosing of chemotherapeutics across widely variable weights within a species. The current BSA formula for dogs lacks height, length, and body condition. Hypothesis Computed tomography (CT) imaging will allow inclusion of morphometric variables in allometric modeling of BSA in dogs resulting in an improved formula for BSA estimation. Animals Forty‐eight dogs from 4 institutions with whole‐body CT images. Methods Retrospective and prospective case series. Body surface area was contoured using whole‐body CT scans and radiation therapy planning software. Body length and height were determined from CT images and also in 9 dogs by physical measurement. Nonlinear regression was used to model the BSA data sets using allometric equations. Goodness‐of‐fit criteria included average relative deviation, mean standard error, Akaike information criterion, and r2 (derived from the r‐value generated by regression models). Results Contoured BSA differed from the current formula by −9% to +19%. Nonlinear regression on untransformed data yielded BSA = 0.0134 × body weight [kg]∧0.4746 × length (cm)∧0.6393 as the best‐fit model. Heteroscedasticity (increasing morphometric variability with increasing BSA) was an important finding. Conclusions and Clinical Importance Computed tomography‐derived BSA was used to incorporate body length into a novel BSA formula. This formula can be applied prospectively to determine whether it correlates with adverse events attributed to chemotherapy.