Analyses for the Presence of a Major Gene Affecting Uterine Capacity in Unilaterally Ovariectomized Rabbits

The presence of a major gene for uterine capacity (UC), ovulation rate (OR), number of implanted embryos (IE), embryo survival (ES), fetal survival (FS), and prenatal survival (PS) was investigated in a population of rabbits divergently selected for UC for 10 generations. Selection was performed on estimated breeding values for UC up to four parities. UC was estimated as litter size in the remaining overcrowded horn of unilaterally ovariectomized does. OR and IE were counted by means of laparoscopy. Bartlett’s test, Fain’s test, and a complex segregation analysis using Bayesian methods were used to test for the presence of a major gene. All three tests showed that the data appeared consistent with the presence of a major gene affecting UC and IE. The results of the complex segregation analysis suggested the presence of a major gene with large effect on IE and ES (a > 1σp), at high frequency (p = 0.70 and 0.68, respectively), and with a large contribution to the total variance (Rg = 0.39 and 0.47, respectively); and the presence of a major gene with moderate effect on each of OR, FS, PS, and UC. The results suggest that the studied reproductive traits are determined genetically by at least one gene of large effect.