Three years ago, the very well managed University commercial cow herd at Cal-State, Fresno started to have a high mortality rate (over 10%) of pre-weaned calves. Cattle raised in the herd had been vaccinated twice at weaning time and given an annual booster for the respiratory diseases such as BVD and IBR. Upon diagnostic testing, a high incidence of “persistently infected” (PI) BVD cattle were found.
Persistently Infected calves can develop in the uterus of their mother, if the cow is exposed to the virus during the first part of gestation, about 40 to 125
days pregnant. Persistently Infected (PI) cattle are often healthy-appearing carriers for BVD virus and are shedding the virus to young, unprotected calves. To get BVD out of the Fresno herds, all animals in both the commercial and purebred herds had a skin notch tested for the virus. The PI carriers were identified and culled from the commercial herd. The purebred herd had no PI carriers. They found that “keeping any PI animals has the risk of re-infecting the whole herd with BVD virus on a daily basis”.
Now the Cal-State, Fresno purebred herd enjoys a marketing advantage of the seedstock cattle they offer for sale. They are one of the first herds in California to have a designation of being free of BVD persistent infection. They are now able to offer cattle that are guaranteed to be persistent infection free. Look for more herds to follow their lead. In fact, Dr. John Maas, California State Extension Veterinarian expects that within a year, many California purebred herds will be tested and offering “PI-BVD-free” bulls and females.
Source: Dr. Randy Perry, Professor Cal-State, Fresno Animal Science Department and Dr. John Maas, State Extension Veterinarian, Univ. Californina-Davis; personal communication.