Responses of registered Jersey cows to various levels
of inbreeding were examined with pedigree data supplied
by the American Jersey Cattle Association and
test-day production data from 1970 through 1998 obtained
from the Animal Breeding Center at Cornell University.
Rate of increase in level of inbreeding is
accelerating with time, making it more difficult for producers
to make matings that avoid the potentially deleterious
effects of inbreeding.
Production losses caused by inbreeding were significant and curvilinear for all
traits studied except somatic cell linear score, with the
greatest losses at higher levels of inbreeding. Inbreeding
was found to have the greatest effect on production
at early ages and early in lactation.
Early onset of the deleterious effects of inbreeding resulted in larger net
present value losses than if effects of inbreeding occurred
later in the life of an animal.
Losses were probably enhanced because of the need to freshen animals as
early as possible to maximize net present value returns.
Survival decreased as level of inbreeding increased and
was likely to have a greater negative impact on the
financial health of the dairy enterprise than production losses.