ENERGY ACQUISITION AND ALLOCATION IN MALE COLLARED LEMMINGS (DICROSTONYX-GROENLANDICUS) - EFFECTS OF PHOTOPERIOD, TEMPERATURE, AND DIET QUALITY

This study examined the effects of photoperiod (long photoperiod [LD, 20L:4D] and short photoperiod [SD, 8L:16D]), temperature (cold [C, 5-d egrees-C] and warm [W, 18-degrees-C]), and diet quality (high-quality diet [HQ, 18% fiber] and low-quality diet [LQ, 49% fiber]) on growth, energy allocation, food intake, digestive efficiency, and gut size in male collared lemmings (Dicrostonyx groenlandicus). Lemmings exposed t o SD at weaning showed an increase in adult body mass relative to anim als from the LD regimens and allocated twofold more energy to growth. Exposure to C increased adult body mass under LD but not SD. Adult bod y mass was reduced in lemmings fed the LQ diet relative to lemmings co nsuming the HQ diet. Lemmings exposed to SD tended to consume less foo d and showed a reduction in digestive efficiency relative to lemmings exposed to LD even though gut size was relatively and absolutely large r under SD conditions. Lemmings acclimated to 5-degrees-C showed an in crease in food intake and digestive efficiency relative to lemmings ac climated to 18-degrees-C The ability to increase digestive efficiency while increasing food intake at 5-degrees-C may have been due to the o bserved increases in the size of the small intestine, cecum, and large intestine. Similarly, the size of the gastrointestinal tract was larg er in lemmings fed the LQ diet than in lemmings consuming the HQ diet. Use of fiber accounted for 32% of metabolizable energy (ME) in animal s fed the LQ, but only 4% of the ME in those fed the HQ.