multiple trait growth QTL 2 Mtgq2 Bwnd4wk2|Bwnd6wk2|Bwnd2wk1|Bwnd5wk2 Bwnd4wk2 http://identifiers.org/mgd/MGI:3723094 MGI:3723094 QTL syntenic QTL O Bwnd6wk2 Bwnd5wk2 Bwnd2wk1