Effects of Different Pellet Feed Hardness on Growth and Reproduction, Feed Utilization Rate, and Environmental Dust in Laboratory Mice / 实验动物与比较医学

ABSTRACT

Objective To study the effects of different pellet feed hardness on the growth and reproduction, feed utilization rate, and environmental dust in laboratory mice.Methods One hundred of fifty 50 3-week-old SPF-grade C57BL/6JGpt and 150 ICR laboratory mice were randomly divided into three groups, with an equal number of males and females. They were fed diets with different hardness of 18.62 kg, 23.15 kg, and 27.89 kg. Body weight, feed utilization rate, and dust levels in cages were recorded and calculated for mice aged 3-10 weeks. Forty-five 6-week-old male mice and ninety 4-week-old female mice from each strain were randomly divided into three groups and fed pellet feeds with three different hardness levels. After 2 weeks of adaptation to the same hardness feed, the mice were paired at a 1∶2 male-to-female ratio and monitored for reproductive data for 3 months.Results At the age of 4 weeks, the body weight of male C57BL/6JGpt mice in 23.15 kg group was significantly higher than that in the 18.62 kg and 27.89 kg groups (P<0.01), and the body weight of females in the 18.62 kg group was significantly higher than that in the 27.89 kg group (P<0.05). There was no significant difference in body weight among ICR mice aged 3-10 weeks across different feed hardness groups (P>0.05). For both strains, feed utilization rate for males was higher than that for females across different feed hardness groups at all weeks of age (P<0.01). Compared to the 27.89 kg group, both the 18.62 kg and 23.15 kg groups showed a significant increase in the 50-mesh dust levels in cages for both strains aged 4-8 weeks (except for 7-week-old C57BL/6JGpt mice) (P<0.05). For both C57BL/6JGpt and ICR mice, there was no significant difference in basic reproductive performance such as interval between the first litter and the monthly production index among the three feed hardness groups during the experimental period (P>0.05). However, the monthly production index of C57BL/6JGpt mice first increased and then decreased with the increase of feed hardness, while that of ICR mice increased with increasing feed hardness, though these differences were not statistically significant (P>0.05).Conclusion Different strains and genders had different tolerance to feed hardness. C57BL/6JGpt mice are more adapted to lower hardness feeds, while ICR mice are better suited to slightly higher hardness feeds.