BONE MARROW FAT CONTENT FROM MOOSE IN NORTHEASTERN MINNESOTA, 1972-2000

Abstract

Percent fat in femur bone marrow has been used as an indicator of animal condition at time of death. However, femur bone marrow is not always available for collection. We used linear regression to examine relationships among marrow fat values for long bones (i.e., femur, tibia, mandible, humerus, radius, tarsal and carpal bones) of moose (Alces alces) from northeastern Minnesota during 1972-2000. Linear regressions for bone marrow fat in each set of bones (paired with femur) in calves and adults were significant and highly correlated (r² = 0.83-0.99). Linear regressions for femur bone marrow fat for yearling moose were significant and highly correlated for tibia, humerus and radius bones (r² = 0.86-0.93), and less so for tarsal bones (r² = 0.63). Bone marrow fat deposition appeared first in proximal and distal bones and was mobilized last in distal bones. Calves had higher femur fat in fall and early winter than late winter and spring. Month, season, and year had no significant effect on femur marrow fat percent for yearlings or adults. Percent femur marrow fat was lower in accidentally killed calves than accidentally killed yearlings or adults. Adults killed by disease had lower percent femur fat than those killed by accident or wolves (Canis lupus). Amount of adult male femur fat was loosely correlated to a winter severity index for the previous winter. Our results suggest that fat deposition and mobilization were similar to that found in other studies and that bone marrow fat content may be a good indicator of relative moose health within a population.