Mice were weighed every 2 days from birth up to weaning and every 5 days thereafter as an index of growth. Mice of both Igf2-KO lines had significantly lower birth weights than their WT littermate controls (a, GENOTYPE, F2,135=147.76, P<0.001). Igf2-total KO mice (N=20) exhibited a ~55% reduction in birth weight relative to WT controls (N=39) (post-hoc: F1,96=265.40, P<0.001); Igf2-P0 KO mice (N=40) exhibited a ~25% reduction in birth weight relative to WT controls (N=39) (post-hoc: F1,116=91.78, P<0.001); the comparison between Igf2-KO P0 and Igf2-total KO was also significant (post-hoc: F1,58=65.72, P<0.001). Growth curves during the first 100 days of postnatal life are shown in b. (c) Dividing the first 100 days of growth into four equal phases for more detailed analysis of growth rates, the Igf2-total KO mice displayed a significant growth spurt during the first 25 days of postnatal life (GENOTYPE, F2,135=6.65, P<0.001; post-hoc, F1,96=13.19, P<0.001), following which growth rate was not different; however, these mice remained ~38% below WT weight at 100 days old (GENOTYPE, F2,135=182.63, P<0.001; post-hoc, F1,96=365.07, P<0.001) (d). Igf2-P0 KO mice underwent a slightly later main period of accelerated weight gain relative to WT controls (c), between postnatal days 25 and 50 (GENOTYPE, F2,135=10.07, P<0.001; post-hoc, F1,116=19.74, P<0.001). At 100 days old (d), the body weight of Igf2-P0 KO mice was still significantly reduced in comparison with WT controls (post-hoc, F1,116=21.08, P<0.001); however, this difference reflected only a ~7% reduction compared with the ~25% difference at birth, suggesting a significant period of accelerated compensatory growth. The differences in body weights were maintained throughout the lifespan, as data from older mice (~400 days old) showed a similar pattern (data not shown). Data are for male mice generated from 19 Igf2-P0 KO and 18 Igf2-total KO litters; ANCOVA was used to analyses all data, co-varying for variance due to the different WT litter-mate control groups. Data are mean+s.e.m., *significant difference from control (α<0.05).