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I vaccinated my cows with a MLV (modified live virus) for IBR/BVD. The cows that were pregnant aborted. Why?

Last Updated: October 27, 2008

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Cattle that are pregnant and vaccinated with a MLV may on a rare occasion abort their fetuses due to infection with the vaccination virus. IBR/BVD are two viruses that can result in early embryonic deaths, stillbirths and weak calves. This will cause a reduction in calf crops due to decreased pregnancy rates, abortions and greater calf mortality. In order to ensure that this does not occur, you should have all herd additions tested for PI (persistently infected) status for BVD virus prior to purchase. Have your veterinarian do a skin biopsy from the ear and send off for immunochemistry skin test. When vaccinating, the most effective for of treatment if a MLV to treat for both BVD and IBR. To administer vaccination, treat replacement heifers at weaning, then give MLV booster one month prior to onset of breeding. Non-pregnant adults should receive MLV vaccine three to four weeks prior to breeding.

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