Fatty acid composition of black bear (Ursus americanus) milk during and after the period of winter dormancy.

Black bears give birth and lactate during the 2-3-mon fast of winter dormancy. Thereafter the female emerges from the den with her cubs and begins to feed. We investigated fatty acid patterns of milk from native Pennsylvania black bears during the period of winter dormancy, as well as after den emergence. Throughout winter dormancy, milk fatty acid composition remained relatively constant. The principal fatty acids at all times were 14:0, 16:0, 16:1, 18:0, 18:1, 18:2n-6, 18:3n-3 and 20:4n-6. After den emergence, large changes occurred in almost all the fatty acids, particularly in 18:2n-6 and 18:3n-3. Large variability among the active free-ranging animals likely reflected differences in diet. In a carnivore, with apparently limited de novo synthesis of fatty acids, milk fatty acid composition may be affected by factors such as transition from reliance on stored lipids to feeding, and by temporal changes in dietary intake.