Dynamics of Food Passing through the Digestive Tract in the Nocturnal Rodent Meriones crassus as a Response to the Rhythm of Feeding Activity

The dependence of the food passing through the digestive tract (DT) on feeding activity in the nocturnal rodent Meriones crassus was studied. Two groups of gerbils were housed in the laboratory under artificial lighting at a photoperiod of 12 : 12 L : D for 36 h. The groups were named “day” (L : D = 20 : 16) and “night” (L : D = 12 : 24) according to the predominance light or dark time during the experiment. The mean retention time of markers in the stomach in these groups was 20 and 30 h, respectively. The kinetics of the contents changed depending on the specific time of consumption of the markers and the saturation level of the rodents with food. During the daylight hours, sequential evacuation of markers entering the DT begins from the stomach after two hours, and at night, during a period of higher feeding activity, part of the food located in the fornix of the stomach and in the cecum stays here for a longer time. In the “day” group, by the end of the experiment, 84% of the markers were removed from the DT, and in the “night” group, about 55%.