Evaluation of mouse lines for maternal performance and growth of offspring.

Crossfostering sets of mice each containing four dams representative of three selected lines (M, W, and B) and one control (C) were prepared in each of two populations (P and Q) to compare nursing ability of the mother and the intrinsic growth potential of the offspring among lines within populations. The descending order of line performance for the nursing ability, as measured by mean 12-day weight of eight offspring within a nursed litter, was M (8.48 g),W (8,47 g), B (7.88 g) and C (7.22 g) in population P; and W (10.16 g), M(9.83 g), B (9.56 g), and C (9.01 g) in population Q. Dams from line W had the heaviest body weight after parturition and consumed 176.7 g of feed in population P and 191.7 g in population Q during 12 days of lactation. The order of lines for growth potential measured by 42-day weight was W (30.83 g), B (24.60 g), M (24.36 g), and C (22.61 g) in population P; and W (40.19 g), B (31.35 g), M (29.98 g), and C (27.81 g) in population Q. These results were compared with those from a conventional line comparison where mothers reared their own offspring. Between the two comparisons, line order differed for nursing ability in population P but not in population Q, and did not differ for 42-day weight.