Crossing selected lines vs. selecting from a cross in mice

Area of Science:

• Animal breeding and genetics
• Quantitative genetics
• Livestock improvement

Background:

• Selective breeding is a cornerstone of animal improvement, aiming to enhance desirable traits.
• Understanding the genetic architecture of traits (e.g., additive vs. non-additive gene action) is crucial for optimizing selection strategies.
• Crossbreeding can potentially increase genetic variation and performance, but its effectiveness varies by trait.

Purpose of the Study:

• To compare the effectiveness of different selection strategies in mice.
• To investigate the impact of crossbreeding prior to selection versus crossing selected lines.
• To determine the influence of genetic inheritance patterns (additive, dominance, epistasis) on trait response to selection.

Main Methods:

• Eight generations of selection for post-weaning body weight gain and litter size at birth.
• Utilized two outbred mouse stocks and a third stock derived from crossing these.
• Compared selection response between crossing selected outbred stocks and selection within a crossbred stock.

Main Results:

• Selection from the crossbred stock yielded greater improvement in post-weaning body weight gain compared to crossing selected outbred stocks.
• This advantage for body weight gain suggests primarily additive gene action, which benefits from increased genetic variation in crossbreds.
• For litter size, a trait influenced by dominance and epistasis, crossing prior to selection showed no clear advantage over other methods.

Conclusions:

• The optimal breeding strategy depends on the underlying genetic basis of the trait.
• Crossbreeding prior to selection is beneficial for traits with predominantly additive genetic effects, like body weight gain.
• For traits with significant non-additive genetic effects, such as litter size, this strategy offers no clear advantage.