The aim of the study was to evaluate the changes in serum biochemistry values in Croatian Mountain Rescue Service dogs included in two different feeding regimes during stimulated fieldwork. There were 12 healthy dogs (age 3.57±1.81) included in the study, divided into two groups: pressed dog food (PRESS group) and raw meat-based diet (BARF group). The diets differed in macronutrients level: on a dry matter basis BARF diet consisted of protein, fat, and carbohydrate in the following proportions: 45.2:32.2:5.5 and kibble diet 27.5:18.7:42.8. During the period of 4 months, blood samples were obtained two times per month: baseline sample in the morning before feeding and the second one immediately after the fieldwork. Results were compared between and within the two groups had shown that pre and post-exercise glucose level was not affected by the type of diet and remained within the reference range. Post-exercise serum levels of lactate within the groups did not differ significantly. Nevertheless, the basal level of lactate was significantly lower in BARF versus PRESS group. The transitory rise in urea and creatinine levels post exercise as well as lower level of inorganic phosphorus was noted in the BARF group, whereas higher basal levels of creatinine and higher post workout levels of inorganic phosphorus were measured in PRESS group. Results within both groups showed higher activity of CK, LDH and AST in both grups post-exercise, as well as lower levels of total cholesterol and Mg. Post-exercise level of TAG was higher in BARF group in comparison to PRESS group. Conducted research reflects different metabolic response to feeding regimes with different macronutrient composition, as well as differences in biochemical parameters as response to processing procedure, especially visible through inorganic phosphate and creatinine level. Stabile glucose level after strenuous fieldwork would indicate excessive metabolic adaptations to the main source of energy provided through observed feeding regimes. An increased ability to utilize fat should be considered an advantage in a dog subjected to prolonged fieldwork in which fatty acid oxidation is used as main energy source. Muscle damage indicators suggest that long period of different intensity level workload in search and rescue dogs result in various physiological processes as well as overall increased muscle activity demands.