Optimization of Cage-Changing Intervals and Wood Shavings Usage for Mice During the Growth Phase in Breeding Systems

doi:10.12300/j.issn.1674-5817.2025.095

Abstract

Abstract:

Objective To determine the optimal bedding depth of wood shavings and cage-changing interval for post-weaning (21-day-old) SPF C57BL/6J mice housed in open cages within a barrier environment. Methods Three bedding groups with average depths of 3 cm, 4 cm, and 5 cm were established, forming six experimental groups (three groups each for female and male mice, with 60 mice per group and 20 mice per cage, totaling 18 cages). The mice were housed in accordance with the maximum housing density requirements specified in GB 14925—2023 Laboratory Animal—Environment and Housing Facilities. Indicators, including body weight, food intake, waste load, and bedding cleanliness, were continuously monitored in mice aged 21-54 days. Results At the age of 21-54 days, the body weight of male mice in the 4 cm bedding group at 42 days was significantly higher than that in the 3 cm and 5 cm groups (P<0.01); at the age of 45-54 days, the waste load of male mice in the 4 cm group was significantly higher than that in the 3 cm group (P<0.05). There were no statistically significant differences in body weight, feed intake and waste load of female mice among each bedding height group (P>0.05). Gender comparison showed that the body weight, feed intake and waste load of male mice were significantly higher than those of female mice at multiple age groups (P<0.05). However, there was no statistically significant difference in cleanliness scores between female and male mice (P>0.05). The scores of mice in the 3 cm and 4 cm groups were close to 3 points from day 6 to day 12, and the scores of mice in the 5 cm group were close to 3 points on day 12. After 42 days of age, the cleanliness scores of each group increased rapidly, and the cage change cycle needed to be shortened to 4 days. Comprehensive recommendation: the cage change cycle for 3 cm and 4 cm bedding heights is 6 days, and it can be extended to 12 days at a height of 5 cm bedding, and shortened to 4 days after 42 days of age. Conclusion Under the open-cage housing mode, a bedding depth of 4 cm combined with a 6-day cage-changing interval during the growth phase can maintain cage cleanliness through bedding adsorption while optimizing the use of bedding resources. This protocol successfully balances animal welfare assurance with facility operational efficiency and is suitable for the large-scale management of C57BL/6J mice and inbred strains with similar genetic backgrounds.

Key words: Wood shavings bedding, Open cages, Bedding depth, Cage-changing interval, C57BL/6J mice

CLC Number:

Q95-33

WU Xianwen,LIU Lili,CHEN Ye,et al. Optimization of Cage-Changing Intervals and Wood Shavings Usage for Mice During the Growth Phase in Breeding Systems[J]. Laboratory Animal and Comparative Medicine, 2026, 46(2): 251-260. DOI: 10.12300/j.issn.1674-5817.2025.095.

Figures/Tables 6

References 21

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评分/分 Score/point	垫料状态 Bedding condition	粪便堆积情况 Fecal accumulation
0	干净、干燥、松散	无可见粪便
1	颜色轻微加深	少量（约占垫料总体积的2%）
2	颜色加深至黄褐色	在一角有明显堆积
3	明显变色，黄褐色加深	堆积量约占笼盒底面积的1/3，可见黑色粪粒堆积
4	深褐色	集中堆积于一侧，约占笼盒面积的1/2
5	严重污染	分布于笼盒两角及中间区域，约占笼盒面积的2/3

评分/分 Score/point	垫料状态 Bedding condition	粪便堆积情况 Fecal accumulation
0	干净、干燥、松散	无可见粪便
1	颜色轻微加深	少量（约占垫料总体积的2%）
2	颜色加深至黄褐色	在一角有明显堆积
3	明显变色，黄褐色加深	堆积量约占笼盒底面积的1/3，可见黑色粪粒堆积
4	深褐色	集中堆积于一侧，约占笼盒面积的1/2
5	严重污染	分布于笼盒两角及中间区域，约占笼盒面积的2/3

日龄/d Age in days/d	3 cm组体重/g Body weight in the 3 cm group/g		4 cm组体重/g Body weight in the 4 cm group/g		5 cm组体重/g Body weight in the 5 cm group/g
日龄/d Age in days/d	雄性小鼠 Male mice	雌性小鼠 Female mice	雄性小鼠 Male mice	雌性小鼠 Female mice	雄性小鼠 Male mice	雌性小鼠 Female mice
21	8.12±0.23	8.89±0.28	8.35±0.29	8.37±0.34	6.59±0.34	8.38±0.50
24	9.31±0.33	10.01±0.56	9.34±0.25	9.81±0.41	8.12±0.58	9.38±0.47
27	11.59±0.32	12.79±0.30	11.80±0.38	11.48±0.33	11.93±0.70	12.07±0.49
30	14.54±0.33	13.86±0.52	14.80±0.49	14.31±0.41	13.85±0.73	14.41±0.43
33	16.55±0.44	15.76±0.41	17.25±0.69^*	15.06±0.39	16.08±0.49	15.68±0.23
36	18.41±0.28^*	15.98±0.42	18.47±0.62^**	16.18±0.42	17.38±0.32^*	16.22±0.33
39	19.75±0.28^*	17.15±0.41	19.97±0.42	17.13±0.39	18.12±0.29^**	17.03±0.23
42	20.06±0.28^*	17.39±0.23	20.75±0.41^a**	17.87±0.20	19.58±0.26^**	17.60±0.23
45	20.51±0.39^**	16.39±0.33	20.29±0.30^**	16.87±0.14	20.65±0.77^**	16.60±0.09
48	21.04±0.34^**	16.53±0.32	21.75±0.35^**	16.91±0.13	20.97±0.65^**	16.50±0.22
51	22.01±0.36^**	16.95±0.23	21.97±0.28^**	17.34±0.08	21.68±0.53^**	17.05±0.03
54	22.58±0.16^**	17.38±0.29	22.35±0.16^**	17.64±0.05	22.15±0.35^**	17.25±0.10

日龄/d Age in days/d	3 cm组体重/g Body weight in the 3 cm group/g		4 cm组体重/g Body weight in the 4 cm group/g		5 cm组体重/g Body weight in the 5 cm group/g
日龄/d Age in days/d	雄性小鼠 Male mice	雌性小鼠 Female mice	雄性小鼠 Male mice	雌性小鼠 Female mice	雄性小鼠 Male mice	雌性小鼠 Female mice
21	8.12±0.23	8.89±0.28	8.35±0.29	8.37±0.34	6.59±0.34	8.38±0.50
24	9.31±0.33	10.01±0.56	9.34±0.25	9.81±0.41	8.12±0.58	9.38±0.47
27	11.59±0.32	12.79±0.30	11.80±0.38	11.48±0.33	11.93±0.70	12.07±0.49
30	14.54±0.33	13.86±0.52	14.80±0.49	14.31±0.41	13.85±0.73	14.41±0.43
33	16.55±0.44	15.76±0.41	17.25±0.69^*	15.06±0.39	16.08±0.49	15.68±0.23
36	18.41±0.28^*	15.98±0.42	18.47±0.62^**	16.18±0.42	17.38±0.32^*	16.22±0.33
39	19.75±0.28^*	17.15±0.41	19.97±0.42	17.13±0.39	18.12±0.29^**	17.03±0.23
42	20.06±0.28^*	17.39±0.23	20.75±0.41^a**	17.87±0.20	19.58±0.26^**	17.60±0.23
45	20.51±0.39^**	16.39±0.33	20.29±0.30^**	16.87±0.14	20.65±0.77^**	16.60±0.09
48	21.04±0.34^**	16.53±0.32	21.75±0.35^**	16.91±0.13	20.97±0.65^**	16.50±0.22
51	22.01±0.36^**	16.95±0.23	21.97±0.28^**	17.34±0.08	21.68±0.53^**	17.05±0.03
54	22.58±0.16^**	17.38±0.29	22.35±0.16^**	17.64±0.05	22.15±0.35^**	17.25±0.10

日龄/d Age in days/d	3 cm组采食量/g Food intake in the 3 cm group/g		4 cm组采食量/g Food intake in the 4 cm group/g		5 cm组采食量/g Food intake in the 5 cm group/g
日龄/d Age in days/d	雄性小鼠 Male mice	雌性小鼠 Female mice	雄性小鼠 Male mice	雌性小鼠 Female mice	雄性小鼠 Male mice	雌性小鼠 Female mice
24	50.67±1.33	65.26±1.73	75.13±1.73	75.72±1.33	61.32±1.22	74.76±1.22
27	101.26±1.45	112.33±1.22	120.27±1.22	120.34±1.45	100.23±2.98	110.54±2.98
30	119.33±2.98	132.16±2.11	132.78±2.11	138.14±2.98	132.66±2.88	132.32±2.88
33	141.55±2.22^*	136.25±3.98	149.62±3.98	141.27±2.22	143.38±2.23	142.36±2.23
36	149.23±3.88^**	137.43±3.55	164.37±3.55	141.96±3.88	159.47±3.96^*	151.28±3.96
39	161.47±2.23^*	138.45±2.66	168.39±2.66	150.22±2.23	170.25±3.74^**	155.33±3.74
42	157.36±4.65^**	140.71±4.74	164.96±4.74^**	145.63±4.65	173.74±4.11^**	150.46±4.11
45	145.33±6.18	141.33±4.67	143.00±5.57	108.33±3.51	151.00±4.73^**	113.00±3.90
48	162.67±4.26^**	135.67±2.60	168.00±3.51^*	134.33±14.67	161.33±5.70	140.33±3.18
51	159.00±2.08	130.33±1.45	165.33±1.45^**	127.33±11.20	159.33±6.36^*	139.00±0.58
54	169.33±4.81	140.67±3.84	155.67±18.48^*	147.00±3.79	165.33±6.12	148.33±1.45