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Bull Fertility Testing/Late Gestation Abortions

March 11, 2015

Bull Fertility TestingBull_Fert

It‘s recommended that breeding bulls undergo a breeding exam/fertility test annually.  Most bull sellers have their
r offerings tested or guarantee they will be satisfactory breeders and pass a test performed latter.  Bulls being sold at less than a year of age and have been developed under a heavy feeding program, may not be quite mature enough or conditioned properly to get a fair test before the selling.  An exam only identifies reproductive soundness on the date of the test.  Since a multitude of things may occur in the interim of a test and when turned out to breeding, a test closer to breeding may be preferred.

North Dakota veterinarians participated in project last spring to summarize incidence and reasons for failure of bulls to pass breeding soundness exams.  Out of almost 6,000 bulls tested 660 failed for an average overall failure rate of 11%.   Within yearling age bulls, the failure rate was 17%, mostly for reasons associated with semen morphology.  Failure rate for rested bulls remained quite high.  DNA testing  of calves from herds running multi sire breeding pastures for sire identification is also interesting in regards to sire fertility and dominance.  We find there are sire(s) often producing no or few progeny within breeding groups.

Late Gestation AbortionsLate_Gestation

It seems most years as calving season approaches we encounter the disappointment of finding  an aborted fetus or a premature stillbirth.   As a biological system we recognize there are likely some early embryos that  didn’t survive and even abortions of fetus that occurred when they were so small they weren’t seen.  A normal number might be about 2% of pregnancies, and any number  greater should causes some concern and diagnostic effort.

Abortions have many causes including genetic defects, hormonal imbalances, metabolic stress, toxicoses, and or infectious disease due to protozoa, bacteria, or virus.  Neosporosis abortions are typically sporadic and believed to be in part spread by carnivorous bird or animals.  Leptospiria bacteria, BVD  and IBR virus can also cause abortion if infections are circulating within the herd.  Cowherd vaccination programs are used with modified live products administered when cows are open, and killed vaccines for safe use on pregnant cows, to maintain immune protection.

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