Developing and evaluating a method for multi-ovulation and embryo transfer (MOET) in the bison (bison bison)

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.