McDonald J M, Nielsen M K
Department of Animal Science, University of Nebraska, Lincoln, NE 68583-0908, USA.
J Anim Sci. 2007 Mar;85(3):658-66. doi: 10.2527/jas.2006-465. Epub 2006 Oct 23.
Divergent selection in mice was renewed in 3 independent replicates for high (MH) and low (ML) heat loss. An unselected control (MC) was maintained in all replicates. Heat loss was measured for individual male mice for 15 h, overnight in direct calorimeters. After 16 initial generations of selection followed by 26 generations of relaxed selection, divergent selection resumed for 9 generations. The realized selection applied was very close to the maximum possible selection according to the criteria and protocol. Selection differentials were greater for high than for low selection due to greater variation in the MH line. When corrected for SD, standardized selection differentials were similar for MH and ML selection. Unintended selection in MC was negligible. Realized heritability for divergence was 0.14 +/- 0.01, which was considerably less than that realized during the initial generations of selection (0.28 +/- 0.03). Realized heritabilities for MH selection (0.16 +/- 0.05) and for ML selection (0.07 +/- 0.06) were less, especially for ML selection, than were observed in the earlier generations. The difference in heat loss between MH and ML males was 55.7% of the MC mean at generation 51, compared with a difference of 53.6% in generation 15; this difference had decreased to 34.4% at the end of the relaxed selection (generation 42). For feed intake between 8 and 11 wk, MH and ML males differed by 34.0% of the MC mean by the end of the selection process. Body weight at 12 wk for MH and ML males was less than for MC males. Litter size response was positively related to the heat loss response. Conception rate was poorer in MH matings than in MC and ML matings.
在3个独立的重复实验中，对小鼠进行了高（MH）和低（ML）热损失的分化选择。在所有重复实验中都维持了一个未选择的对照组（MC）。在直接热量计中，对单个雄性小鼠进行15小时的热损失测量，测量时间为过夜。经过16代初始选择，随后进行26代的放松选择，然后又进行了9代的分化选择。根据标准和方案，实际应用的选择非常接近最大可能选择。由于MH品系的变异较大，高选择的选择差大于低选择。校正标准差后，MH和ML选择的标准化选择差相似。MC中的非预期选择可以忽略不计。分化的实际遗传力为0.14±0.01，远低于初始选择代（0.28±0.03）的遗传力。MH选择（0.16±0.05）和ML选择（0.07±0.06）的实际遗传力较低，尤其是ML选择，低于早期代次的观察值。在第51代时，MH和ML雄性小鼠之间的热损失差异为MC平均值的55.7%，而在第15代时为53.6%；在放松选择结束时（第42代），这一差异降至34.4%。在选择过程结束时，8至11周龄的MH和ML雄性小鼠的采食量差异为MC平均值的34.0%。MH和ML雄性小鼠12周龄时的体重低于MC雄性小鼠。窝产仔数反应与热损失反应呈正相关。MH交配的受孕率低于MC和ML交配。
