Table 2.

Reproductive parameters of mice according to enrichment condition

Strain	Enrichment	No. of pups born	Pups weaned		Weight (g) of pupsa		Time (d) to 1st litter or interlitter interval
			Total no.	%	Male	Female
BALB/c
Nest (n = 119)b		28.4 ± 1.4	24.8 ± 1.4	87.3	11.0 ± 0.2	11.0 ± 0.2	32.6 ± 1.0c
Nest and shelter (n = 113)		24.3 ± 1.6	22.6 ± 1.6	93.0	11.5 ± 0.1	11.4 ± 0.1	28.0 ± 1.1d
Nest, shelter, and wheel (n = 117)		27.0 ± 1.2	25.3 ± 1.3	93.7	11.6 ± 0.1	11.5 ± 0.1	29.2 ± 0.9d
129/Sv
Nest (n = 113)		21.6 ± 1.4	16.8 ± 1.4e	77.8	12.1 ± 0.2	12.0 ± 0.1	30.0 ± 1.0
Nest and shelter (n = 111)		23.6 ± 1.5	21.1 ± 1.7f	89.4	12.9 ± 0.2	12.5 ± 0.1	30.9 ± 1.2
Nest, shelter, and wheel (n = 115)		23.7 ± 1.5	22.1 ± 1.5f	93.2	12.8 ± 0.2	12.6 ± 0.2	30.1 ± 1.1

Data are shown as mean ± SEM. Within each parameter, values with different letters differ significantly (P < 0.05).

^aAt weaning (day 21).

^bLitter was used as the unit of measurement to compile means and SEM.