Sled dogs are known to develop numerous serum biochemical changes due to endurance exercise. Previous studies have suggested that mild hyponatraemia and hypokalaemia can develop during endurance racing. The aim of the present study was to determine if serum biochemical alterations are similar to previous reports, and if electrolyte alterations are still present with present feeding practices utilised by mushers. Serum chemistries were obtained from 26 Alaskan Huskies belonging to 3 different teams, before and after a 1600 km race. Meals and snacks were analysed via calculation to determine daily macronutrient and electrolyte intake. Numerous biochemical alterations were observed including significant differences in serum total protein, albumin, globulin, aspartate aminotransferase, creatine kinase, TAG, NEFA and urea nitrogen (P < 0·05). Serum electrolyte status revealed a mild, yet significant decrease in serum sodium (P = 0·002); and serum potassium was not significantly different (P = 0·566). Further examination of the sodium intake across the three teams revealed two teams with an average daily intake of approximately 8·5 g/dog/d (700 mg/4184 kJ) and the other team consuming 11·1 g/dog/d (1200 mg/4184 kJ). Regression analysis shows a significant modest positive correlation between serum sodium decrease and sodium intake per metabolic body weight of the dogs, as well as a modest positive correlation between sodium intake and serum potassium implicating the renin–angiotensin aldosterone system as a major factor involved in sodium and potassium homoeostasis. These findings suggest that consumption of approximately 0·9 g/kg0·75 (1·2 g/4184 kJ) of sodium per d may prevent exercise-induced decreases in sodium and potassium.

A dog's nutrient requirements can theoretically be met from a properly balanced meat-free diet; however, proof for this is lacking. Exercise places additional demands on the body, and dogs fed a meat-free diet may be at increased risk of developing sports anaemia. We hypothesised that exercising dogs would remain in good health and not develop anaemia when fed a nutritionally balanced meat-free diet. To this end, twelve sprint-racing Siberian huskies were fed either a commercial diet recommended for active dogs (n 6), or a meat-free diet formulated to the same nutrient specifications (n 6). The commercial diet contained 43 % poultry meal, whereas soyabean meal and maize gluten made up 43 % of the meat-free diet, as the main protein ingredients. Dogs were fed these diets as their sole nutrient intake for 16 weeks, including 10 weeks of competitive racing. Blood samples were collected at weeks 0, 3, 8 and 16, and veterinary health checks were conducted at weeks 0, 8 and 16. Haematology results for all dogs, irrespective of diet, were within normal range throughout the study and the consulting veterinarian assessed all dogs to be in excellent physical condition. No dogs in the present study developed anaemia. On the contrary, erythrocyte counts and Hb values increased significantly over time (P < 0·01) in both groups of dogs. The present study is the first to demonstrate that a carefully balanced meat-free diet can maintain normal haematological values in exercising dogs.

Five previously untrained yearling sled dogs were evaluated for endurance training-induced changes in maximum oxygen consumption (VO2max) and submaximal blood lactate concentrations. Following 3 weeks of light training followed by 4 weeks of moderate training, VO2max increased by 10%, from 180.2 ± 9.9 to 198.7 ± 19.2 ml kg min− 1 (P = 0.046). Light training was not associated with any increase in VO2max. Blood lactate concentrations at the same absolute intensity decreased by 215%, from 9.2 ± 4.7 to 4.3 ± 2.4 mmol l− 1 (P = 0.022). Speeds associated with oxygen consumptions of 70% VO2max increased by 12%, from 4.8 ± 0.4 to 5.4 ± 0.5 m s− 1 (P = 0.008) and speeds associated with VO2max increased by 21%, from 6.7 ± 0.3 to 8.2 ± 0.7 m s− 1 (P = 0.012).

Humans undergoing intense exercise exhibit transient microalbuminuria. Previous studies have shown that swimming, but not running, induces microalbuminuria in dogs. In this study, urine samples were collected from nineteen well-conditioned Alaskan sled dogs and analysed by the Heska ERD-Screen Test for microalbuminuria. None of the dogs has microalbuminuria, indicated that well-trained dogs do not develop microalbuminuria after running. Further studies are needed to determine if these dogs do develop microalbuminuria after competition or longer-distane runs.