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Hereford and Red Angus Heifers Recruited for Genomics Research

The University of Missouri is recruiting 2,500 Hereford heifers and 2,500 Red Angus heifers to participate in a heifer puberty and fertility genomic research project. Heifers should be registered Hereford, registered Red Angus, or commercial Hereford or Red Angus. Hereford x Red Angus crossbred heifers targeted for the Premium Red Baldy Program would also be a good fit for the research project. Producers must be willing to work with a trained veterinarian to collect the following data: ReproductiveTract Scores collected at a pre-breeding exam 30 to 45 days prior to the start of the breeding season. PelvicMeasurements (height and width) collected at the same pre-breeding exam 30 to 45 days prior to the start of the breeding season. Pregnancy Determination Using Ultrasound reporting fetal age in days. Ultrasound will need to occur no later than 90 days after the start of the breeding season. In addition, heifers must have known birth dates and have weights recorded eithe

BIF 2019: Timed AI with Sex-Sorted Semen: Research and Applications in Commercial Beef Herds

Jordan Thomas
University of Missouri
NAAB Symposium

Why do we care about sex sorted semen?
For any on mating, one sex of calf is always more valuable. This is due to genetic potential and your marketing program.

What is the value difference?
What is the true cost of using sex sorted semen?
Does the value difference justify the cost?

In a perfect world, pregnancy rates would be identical between conventional and sex-sorted semen. But, this is not true. Further, the bull you want to use may not have sex-sorted semen available due to sorting or fertility factors. Sex-sorted semen is also very sensitive to the timing of estrus in a timed synchronization program. Lastly, sex-sorted semen is not free! There are direct costs (cost per straw of semen) and indirect cost (lower pregnancy rates, estrus detection, more complicated protocols).

Unlike the dairy industry, we have a fixed breeding season in the beef industry. If a dairy cow is not breed using sex-sorted semen, we just AI her another time.

Can we optimize male fertility based on how we manage cows in a timed AI program? That is the main research question Thomas is working to answer.

What do we do about cows that don't express estrus at the time of fixed time AI? We can do Split-Time AI, in which we breed cows in groups based on when they express estrus. At 66 hours we bred all of the cows that have expressed estrus. For those cows that have not expressed estrus, we wait 24 hours and breed them.

Ninety percent of heifers express heifers in a split-timed AI protocol. With split-timed AI, Thomas' research observed a 60% pregnancy rate in heifers using conventional semen, and a 52% pregnancy rate when using sexed sorted semen. Non-estrous heifers had a 29% pregnancy rate.

In mature cows, split-timed AI protocols have less consistent results.

To learn more about split-timed AI visit https://extension2.missouri.edu/mp739.

Also check out Mizzou Repro on Facebook, YouTube and Instagram.

Sex-sorted semen allows us to develop terminal and maternal lines, in either a crossbreeding or straightbreeding programs.



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