Some of the risks include (taken from http://www.flightpathfarms.com/beefalo-library/utilizing-high-percentage-bison-hybrids-in-your-breeding-program/ , by Paul Butler)
- "Lower conception rates
- Higher levels of early embryonic loss. This is characterized by cows that conceive, miss one to four heat cycles, then show heat again. Higher levels of later-term abortions (often seen around the 5 th or 6 th month of pregnancy).
- Possible development of polyhydrominos condition. Commonly called “hydrops”, this is basically a partial rejection of the fetus by the mother, resulting in excess buildup of amniotic fluid in the uterus. This condition can range from mild to severe. In severe cases, the result can be the loss of both the fetus and the cow.
- Possible development of a type of protein poisoning. Here again, this is the result of a genetic disparity between the fetus and its mother. This condition usually results in one of three scenarios: 1. The cow aborts the fetus. 2. The cow aborts the fetus and subsequently dies (usually a few days after the abortion). 3. The cow dies.
- Possible severe calving problems. Sometimes a mating results in extreme levels of hybrid vigor in the unborn calf. The calf can become very large before the cow is signaled to give birth. This can happen even with normal gestation lengths.
- Possible non-viable calves. These are calves which are stillborn or which seem very weak when they are born. These very weak calves almost never survive.
- Problems with the cows rebreeding after delivering a calf from this type of mating.
- Problems with male fertility in the offspring of a high-percentage bison hybrid mating. Many times, the bull calves that do result from breeding a 75% bison bull to domestic cows never develop fertility."
In spite of these many risks, we decided we'd go ahead and try it! so far we have 3 calves from Magnum Gold on the ground! All three are heifers and are beautiful. We may have had a few that had embryonic loss. but all in all, we have had good success thus far with breeding to a high percentage Bison bull!