Systematic crossfostering within control lines.
D000818:Animals; D000831:Animals, Newborn; D001835:Body Weight; D003433:Crosses, Genetic; D005260:Female; D014644:Genetic Variation; D008297:Male; D008425:Maternal Behavior; D011247:Pregnancy; D051381:Rats; D012641:Selection, Genetic; D013223:Statistics as Topic; D014886:Weaning