Feeding Behavior of Mice under Different Food Allocation Regimens

Abstract

Social interaction, a basic survival strategy for many animal species, helps maintain a social environment that has limited conflict. Social dominance has a dramatic effect on motivation. Recent evidence suggests that some primate and nonprimate species display aversive behavior toward food allocation regimens that differ from their peers. Thus, we examined the behaviors displayed by mice under different food allocation regimens. We analyzed changes in food intake using several parameters. In the same food condition, the mice received the same food; in the quality different condition, the mice received different foods; in the quantity different condition, one mouse did not receive food; and in the no food condition, none of the mice received food. To test differences based on food quality, one mouse received normal solid food as a less preferred reward, and the other received chocolate chips as a high-level reward. No behavioral change was observed in comparison to the same food condition. To test differences based on food quantity, one mouse received chocolate chips while the other received nothing. Mice who received nothing spent more time on the other side of the reward throughout the experiment. Interestingly, highly rewarded mice required more time to consume the chocolate chips. Thus, under different food allocation regimens, mice changed their behavior by being more hesitant. Moreover, mice alter food intake behavior according to the social environment. The findings help elucidate potential evolutionary aspects that help maintain social cohesion while providing insights into potential mechanisms underlying socially anxious behavior.

Figure 1

Comparison of the latency to begin eating 6 food units. Comparison of the latency to start eating the 6 food units in various conditions of the feeding behavioral test (same food condition, n = 24; quality different condition, n = 12; quantity different condition, n = 16; no food condition, n = 20; asocial condition, n = 20; stuffed cage-mate condition, n = 16). The upper row shows the subject mice ((a)–(d)), and the lower row shows the cage-mate mice ((a′)–(d′)). Data are presented as means ± SEM. Statistical significance is represented by asterisks: ^∗p < 0.05. The p values were calculated using a two-way repeated measures ANOVA.

Figure 2

Comparison of the distance traveled per 1-minute period. Comparison of the distance traveled in each 1-minute period in various conditions of the feeding behavioral test (same food condition, n = 24; quality different condition, n = 12; quantity different condition, n = 16; no food condition, n = 20; asocial condition, n = 20; stuffed cage-mate condition, n = 16). The upper row shows the subject mice ((a)–(e)), and the lower row shows the cage-mate mice ((a′)–(e′)). Data are presented as means ± SEM. Statistical significance is represented by asterisks: ^∗p < 0.05. The p values were calculated by a two-way repeated measures ANOVA.

Figure 3

Comparison of the time spent per 1-minute in the food area. Comparison of the time spent in the food area in each 1-minute period in various conditions of the feeding behavioral test (same food condition, n = 24; quality different condition, n = 12; quantity different condition, n = 16; no food condition, n = 20; asocial condition, n = 20; stuffed cage-mate condition, n = 16). The upper row shows the subject mice ((a)–(e)), and the lower row shows the cage-mate mice ((a′)–(e′)). Data are presented as means ± SEM. Statistical significance is represented by asterisks: ^∗p < 0.05. The p values were calculated by a two-way repeated measures ANOVA.

Figure 4

Feeding behavioral test of chocolate chip beyond the wall condition. Comparison of the distance traveled in each 1-minute period (a) (no food condition, n = 20; beyond the wall condition, n = 12). Comparison of the time spent in the food area in each 1-minute period (b). Data are presented as means ± SEM (a, b). Statistical significance is represented by asterisks: ^∗p < 0.05. The p values were calculated by a two-way repeated measures ANOVA (a, b).

Figure 5

Testing apparatus of the feeding behavioral test. (a) Schematic diagram of the feeding behavioral test. Two mice were placed at the end of the lane simultaneously. The rewards were placed on the opposite side of the lanes. (b) Sample picture during the feeding behavioral test. The test mouse freely moved in the lane. (c) A sample image of the chocolate chips as a high-appeal reward, 0.05 g per unit. (d) A sample image of the ordinary crushed solid food as a low-appeal reward, 0.02 g per unit. (e) A sample picture of the 6 chocolate chips in the testing apparatus. (f) A sample picture of the feeding behavioral test. Subject mice and cage-mate mice were separated by transparent acrylic walls.