Asymmetries, heterosis, and phenotypic profiles of red junglefowl, White Plymouth Rocks, and F1 and F2 reciprocal crosses.

During the domestication of farm animals, humans have manipulated genetic variation for growth and reproduction through artificial selection. Here, data are presented for growth, reproductive, and behavior traits for the red junglefowl, a line of White Plymouth Rock chickens, and their F1 and F2 reciprocal crosses. Intra- and intergenerational comparisons for growth related traits reflected considerable additive genetic variation. In contrast, those traits associated with reproduction exhibited heterosis. The role of sexual selection was seen in the evolution of prominent secondary sexual ornaments that lend to female choice and male-male competition. The large differences between parental lines in fearfulness to humans were only mitigated slightly in the intercross generations. Whereas, overall F1 generation heterosis was not transferred to the F2, there was developmental stability in the F2, as measured by relative asymmetry of bilateral traits. Through multigenerational analyses between the red junglefowl and the domestic White Plymouth Rocks, we observed plasticity and considerable residual genetic variation. These factors likely facilitated the adaptability of the chicken to a broad range of husbandry practices throughout the world.

Dual functioning ovaries and atresia in chickens. Is it a coincidence?

During the course of a QTL study involving an intercross between White Plymouth Rock chickens and Red Jungle Fowl, certain reproductive anomalies such as atresia and double ovary-oviduct became evident. Observed in reciprocal pedigreed F1 crosses were 2 full-sib pullets with dual functioning ovaries. One also had complete functioning left and right oviducts. The other had asymmetrical reproductive tracts with a typical left oviduct and a rudimentary right oviduct. In addition, there were 3 females with atresia. Although they had different sires and dams, their grandparents were related, and all 5 traced to a common ancestor. Pedigrees, photos, and biological aspects of these conditions are presented and discussed.