Hamsters, like guinea pigs and gerbils, eat regularly, at 2-hour intervals throughout the day (Anderson and Shettleworth, 1977; Borer et al., 1979). Wild hamsters gather and store grains and other food in underground burrows to ensure a constant source of food (Borer et al., 1979; Micheli and Malsbury, 1982; Carleton and Musser, 1984). Hamsters are adapted to running and digging and are active primarily during twilight and during the night.
The golden hamster has a gestation period of 15 to 18 days. Members of the Mesocricetus species are solitary animals that live in separate burrows with one or two chambers and entrances and exits; males and females meet only for breeding (Murphy, 1985).
REPRODUCTION AND DEVELOPMENT
Developmental and reproductive indices for three species are given in Tables 5-2 and 5-3, respectively. Young hamsters weigh 2 to 4 g at birth (see Table 5-4; Poiley, 1972). Average litter size is 11 (Slater, 1972), ranging from 2 to 16 (Anderson and Shina, 1972). Newborn hamsters are fetal in appearance—hairless, eyes and ears closed, and legs underdeveloped (Balk and Slater, 1987). Incisors are erupted at birth and young animals begin to eat solid food within 7 to 10 days (Balk and Slater, 1987). Hamsters weigh 40 g when weaned at 21 days (Poiley, 1972). Male hamsters are sexually mature at 42 days old, but females can breed as early as 28 to 30 days old (Selle, 1945; Balk and Slater, 1987). Litters with the greatest average number of pups are obtained from females 8 to 10 weeks old and males 10 to 12 weeks old (Robens, 1968; Balk and Slater, 1987).
EXAMPLES OF PURIFIED AND NATURAL-INGREDIENT DIETS
Two examples of purified diets and one of a natural-ingredient diet are presented in Tables 5-5 A-C, 5-6 A-C, and 5-7 A-C. These diets supported growth that was equivalent to the highest rates reported in our review of the literature. The two purified diets supported growth rates of 1.6 to 2.0 g/day. The natural-ingredient diet was selected from three that supported a growth rate of 1.9 g/day; of the three, it was intermediate in complexity.
WATER AND ENERGY
Male and female golden hamsters consume, on average, 8.5 mL water/100 g BW/day; males consumed 5 mL water/100 g BW/day, while females consumed 14 mL water/100 g BW/day (Fitts and St. Dennis, 1981). Thompson (1971) recorded Chinese hamsters intake of water to be 11.4 mL/100 g BW/day for males and 12.9 mL/100 g BW/day for females. Water intake for golden hamsters was found to be 4.5 mL/100 g BW/day in males and 13.6 mL/100 g BW/day for females.
Little definitive work has been done on the energy requirement of the hamster, and few research studies include data on energy utilization. When fed a cereal-based diet containing 14.95 percent neutral detergent fiber (NDF) and 5.6 kcal gross energy (GE)/g diet (23.4 kJ/g diet), hamsters digested 45.2 percent of NDF and 81.5 percent of GE. Hamsters fed a 75 percent alfalfa meal diet that contained 40.6 percent NDF and 4.05 kcal GE/g diet (16.9 kJ/