PSI-B-41 Late-Breaking: Effect of age, sex, reproductive status, body composition, and environmental temperature on the basal metabolic rate of working Labrador Retrievers

As the pet industry continues to grow, understanding the needs of different demographics of canines is becoming increasingly important to ensure optimal nutrition. Energy requirements have been shown to vary based on individual factors, but few trials using many dogs under the same controls exist. The objective of this study was to investigate the effect of age, sex, reproductive status, body composition, and environmental temperature on the BMR of Labrador Retrievers (Labs). An open-circuit indirect calorimetry machine attached to a chamber was used to determine resting BMR in 96 Labs. Body composition in 33 Labs of varying age was determined using DXA scans to determine effect of lean/fat mass on BMR. Cooling and heating implements were applied to the chamber to determine temperature effect on BMR. Each of the following demographics were compared using a mixed model: male, female, intact, altered, young (6mo-2yo), adult (3-6yo), and senior (7yo+). Mean BMR for all dogs was 130 (27) kcal/kg0.75. Males were significantly higher at 136 (28) kcal/kg0.75 than females at 125 (25) kcal/kg0.75 (P = 0.045). Intact Labs were significantly higher at 121 (3) kcal/kg0.75 compared to altered Labs at 109 (25) kcal/kg0.75 (P < 0.001). Young and adult Labs had BMRs of 136 (19) kcal/kg0.75 and 135 (29) kcal/kg0.75, respectively, which was significantly higher than seniors at 120 (26) kcal/kg0.75. Body composition comparisons showed significant negative linear relationships between BMR and fat mass (P < 0.001) and positive linear relationships between BMR and lean mass (P < 0.001). BMR was found to have a negative linear relationship (R2=0.51) from cool to warm temperatures but was elevated at both cold (< 5°C) and hot (>35°C) temperatures (P < 0.001). The determination of energy requirements found in this study prove useful as the pet industry develops diets specific to the needs of different demographics of canines.