Eisen E J, Durrant B S
J Anim Sci. 1980 Mar;50(3):428-41. doi: 10.2527/jas1980.503428x.
Lines of mice which have been genetically differentiated in litter size at birth and 6-week body weight by single-trait or index selection were randomly assigned to be reared in postnatal litter sizes (PLS) of N8, N12 or N16. The lines were selected as follows: large litter size (L+), large 6-week body weight (W+), selection index to decrease litter size and increase 6-week body weight (L-W+), selection index to increase litter size and decrease 6-week weight (L+W-) and random selection (K). Line and PLS differences in female body weight at weaning and 6 weeks were significant (P less than .05), with W+ greater than L+ greater than L-W+ greater than K greater than L+W- and N8 greater than N12 greaater than N16. Although there was a significant interaction between line and PLS, ranking of the lines was the same at each PLS. Females of each line by PLS group were exposed to males of the same group. Line and PLS differences (P less than .05) in female body weight at copulatory plug, adjusted for age, exhibited the same rankings as the earlier weights. Litter size at birth (dead plus alive), number born alive and number born alive per female exposed each revealed similar differences (P less than .05) in the ranking of lines and PLS. No significant interactions were found. Means for litter size were as follows for each line: L+ (17.4) greater than [W+ (14.1), L+W- (14.3)] greater than K (12.0) greater than L-W+ (10.8), and for each PLS: [N8 (14.0), N12 (13.9)] greater than N16 (13.2). The decline in litter size as PLS increased did not differ significantly from linearity. Adjusting litter size for body weight at copulatory plug eliminated the significant effect of PLS [N8 (13.9), N12 (13.7), N16 (13.4)]. The established genetic differences in litter size among lines due to selection were considerably larger than the maternal environmental effect due to postnatal litter size. Because of the negligible interaction between line and PLS, valid inferences concerning genetic differences among lines in litter size may be made at any postnatal litter size between eight and 16.
通过单性状或指数选择在出生时的窝仔数和6周龄体重方面具有遗传差异的品系小鼠，被随机分配到出生后窝仔数（PLS）为8只、12只或16只的环境中饲养。这些品系的选择如下：大窝仔数（L+）、6周龄时体重较大（W+）、降低窝仔数并增加6周龄体重的选择指数（L-W+）、增加窝仔数并降低6周龄体重的选择指数（L+W-）以及随机选择（K）。断奶时和6周龄时雌性体重的品系和PLS差异显著（P小于0.05），W+＞L+＞L-W+＞K＞L+W-且N8＞N12＞N16。尽管品系和PLS之间存在显著的交互作用，但在每个PLS下各品系的排名相同。每个品系按PLS分组的雌性与同组雄性交配。交配栓时经年龄校正的雌性体重的品系和PLS差异（P小于0.05）呈现出与早期体重相同的排名。出生时的窝仔数（死胎加活胎）、活产仔数以及每只受配雌性的活产仔数在品系和PLS的排名上均显示出类似的差异（P小于0.05）。未发现显著的交互作用。各品系的窝仔数均值如下：L+（17.4）＞[W+（14.1），L+W-（14.3）]＞K（12.0）＞L-W+（10.8），各PLS的窝仔数均值如下：[N8（14.0），N12（13.9）]＞N16（13.2）。窝仔数随PLS增加而下降，与线性关系无显著差异。以交配栓时的体重校正窝仔数后，PLS的显著效应消失[N8（13.9），N12（13.7），N16（13.4）]。由于选择导致的品系间窝仔数的既定遗传差异远大于出生后窝仔数造成的母体环境效应。由于品系和PLS之间的交互作用可忽略不计，因此在8至16只之间的任何出生后窝仔数下，都可以对品系间窝仔数的遗传差异做出有效的推断。
