Rectovaginal constriction in Jersey cattle: genetics and breed dynamics.

Data from farmer-owned herds and from experimental matings supported monofactorial recessive inheritance of rectovaginal constriction in US Jersey cattle. Kempthorne's population genetics model of a recessive trait involving only male selection was extended to include mutation and converted to selection of females only. Computer analyses with that model estimate slow decline in the frequency of the gene for rectovaginal constriction. Practical dynamics of the disorder in a breed registering 50,000 females and 2,000 males annually are given for current conditions and after 500 generations of selection.