Feeding of a high protein, low carbohydrate diet leads to greater postprandial energy expenditure and fasted n6: n3 fatty acid ratio in lean, adult dogs compared to a moderate protein, moderate carbohydrate diet.

High protein, low carbohydrate (HPLC) diets are often sought out by dog owners. They are reported to have beneficial effects on energy expenditure (EE), fat oxidation, and may alter the serum fatty acid profile. However, there is little to no data to support the feeding of HPLC diets to healthy adult dogs. Thus, the objective of the present study was to interrogate the health claims related to the feeding of HPLC diets to healthy adult dogs using a commercially available HPLC diet (48% of metabolizable energy (ME) from protein, 10% of ME from nitrogen-free extract; NFE), a moderate protein, moderate carbohydrate (MPMC) diet (28% of ME from protein, 39% of ME from NFE) formulated with the same ingredients as HPLC, and a commercially available, MPMC, high fiber, "metabolic" (MET) diet (30% of ME from protein, 37% of ME from NFE) as a commercial control. Diets were fed to 9 healthy, large breed dogs for 42 d in a Latin square design. Fasted blood samples were collected on days -2 (baseline), 12, 26 and 40, and indirect calorimetry was performed on 8 dogs on days 20 and 39 to measure respiratory quotient (RQ) and EE. Statistics were performed in SAS Studio (version 9.4). Dogs fed HPLC had a lower RQ at fasted (0.76), 0 to 4 h (0.78) and 5 to 10 h (0.83) post-meal compared to dogs fed MET (0.80, 0.83, 0.90) and MPMC (0.80, 0.84, 0.91; P < 0.05). All dogs had a similar EE at fasted but dogs fed HPLC had a greater postprandial EE at 0 to 4 h (5.36 kcal/kg^0.75) and 5 to 10 h (5.46 kcal/kg^0.75) compared to dogs fed MPMC (4.79 and 4.84 kcal/kg^0.75; P < 0.05). Dogs fed MET (4.98, 4.96 kcal/kg^0.75) were similar to both (P > 0.05). Alpha-linolenic acid (ALA; 18:3n3), docosapentaenoic acid (DPA; 22:5n3) and total n3 were all greater in dogs fed MET at each week (P < 0.05). In contrast, total n6: n3 and arachidonic acid (ARA; 20:4n6): eicosapentaenoic acid (EPA; 20:5n3) were both greater (P < 0.05) in dogs fed HPLC and MPMC compared to dogs fed MET at each week. This study represents the first to assess EE and serum fatty acids in adult large breed dogs consuming a HPLC diet for 6 wk. Consuming a HPLC diet led to potential beneficial effects of increased EE and fat oxidation after a meal, which has the potential to be useful in managing obesity, a common health concern in dogs.