Abstract:
The idea of domesticating bison is a goal for some cattlemen, who believe in
utilizing the hardiness, long life, foraging habits and feed conversion abilities
of the bison in the production of animal protein. It was not until the
population of millions of bison, that once roamed the USA ranges, had been
reduced to only a few hundred head, that anybody seriously took an active
interest in restoring the numbers of these unique animals.
Reproductive studies on the bison have shown that anatomically and
physiologically they are very similar to domestic cattle. One notable
difference is the apparent seasonality (Table 2.1) of the bison. Bison
breeders indicate that bison are seasonally polyestrous, having a cycling
season during the late summer and continuous into late autumn. Other bison
breeders consider the breeding season to be shorter, ranging from summer to
autumn. This observed shorter duration may be partly due to the fact that
increased breeding activity is observed only during the early part of the
season. Cows that do not conceive early in the season, often do not become
pregnant as they are subjected to the stress of winter and the consequent
decrease in the quality and quantity of nutrition. Anatomically, bison have small ovaries and reproductive tracts, which could
be compared to that of first-calf beef heifers. Consequently, follicles and
CL's are smaller and more difficult to identify by rectal palpation.
Problems associated with the use of reproductive techniques, such as
superovulation and embryo transfer in the bison, are not the technologies as
such, but the handling and management of the animals. Most bison are not
amenable to domestication and are managed as wild animals. The bison
therefore responds accordingly and are often dangerous when handled. The
stress encountered during these procedures on the animal is also a factor that
could affect the response of the bison to superstimulation.
A compounding problem with the few animals still left in the early 1900's, hints
that the bison can experience a serious inbreeding problem. This problem
has led to early abortions and birth defects in many cases. A need has
therefore arisen to increase the number of bison in order to create various
bloodlines. One of the more economical and feasible ways to increase the
bison numbers and achieve this goal is by making use of reproductive
technologies such as embryo transfer, in vitro fertilization and artificial
insemination (AI). Embryo transfer has the advantage of accelerating the
rate of genetic progress and increasing the number of offspring produced.
This study thus looks at the possibility of using accelerated breeding
techniques generally implemented in domestic cattle to help increase the
bison numbers and potential meat production.
