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Here we go again-another rambling on BVD.
Article upon article state that animals persistently infected (PI) with bovine viral diarrhea virus (BVDV) are considered to be the most effective transmitters of the disease. The main route of transmission is by direct contact between PI’s and susceptible animals. Primary BVDV-infected cattle are also potential virus transmitters; however, the virusemia infection period is short and transient. Even though they do shed BVDV in most secretions during the course of infection it is substantially lower from the PI cattle.
This is the basis of my rambling.
In a previous article, I stated in feedlot cattle, some studies are showing an increase of respiratory (BRDC) morbidity, mortality and increased medication cost with reduced performance. The more I evaluate this infection at my research facility, the more I question these previous studies.
Data on 640 head of medium risk-put together cattle done here at my research facility.
The PI-BVD calves were identified using the IHC (immunhistochemistry) ear notch test. The animals were then left in their home pens so their pen mates and also the adjacent pens could be exposed.
ADG COG F/E
All pens
except PI-BVD pens 3.96 $0.3975 5.50
PI-BVD Pens 4.02 $0.3814 5.25
PI-BVD Pens plus Adjacent Pens 4.20 $0.3756 5.14
All cattle except PI-BVD
& Adjacent 3.92 $0.4016 5.57
We have also finished working on another study involving 160 head of previously vaccinated backgrounded cattle in our individual consumption comparison GrowSafe, Inc pens. Two PI-BVD heifers were co-mingled with each pen of 40 head of steers thus 8 PI-BVD calves were exposing 160 animals throughout the entire feeding period. The four pens are also adjacent to each other. The PI-BVD calves (one with mucosal disease was euthanized at the end of the study) did not cause any increased morbidity or decreased performance. The remaining 7 head went to slaughter as scheduled with the 160 steers. The entire 160 head individual data is being evaluated now.
With this info you can see with properly designed comparison studies I don’t think the PI-BVD theory is totally correct.
I’m still convinced testing at the feed yard level is not necessary. We are an alarmist industry.
I am still concerned about the PI-BVD animal in the cowherd. As previously written, the control of BVDV associated diseases in cattle ultimately depends on the identification and removal of the PI animal (cow or calf) in the cowherd prior to the breeding season. This would prevent the PI-BVD calf from exposing the susceptible cow during the 45-70 gestation period and also prevent the PI-BVD calf ever arriving at the feed yard.
However, I am not convinced humanely sacrificing the PI-BVD calf identified at the ranch is the way to go either.
At the time of this writing, we are feeding out 12 animals that were previously tested positive for PI-BVD at the cowherd level. The animals will be here approximately for 200 to 225 days. The results will be included in a later newsletter.
We have mentioned in a previous newsletter about the various methods that have been developed to identify the PI-BVD animal; however, there are only two tests that are routinely used. These are antigen captive (AC) ELISA and immunohistochemistry (IHC). Fresh ear notches are required for the AC ELISA test and fixed ear notches in formalin for the IHC testing.
Controlling BVDV depends upon identifying and removing the PI animal, designing a program to handle the positive animal (possibility finding a facility similar to mine and feed them to slaughter weight), implementing a biosecurity program to prevent re-introduction of BVDV into the cow herd, and implementing a vaccination program to increase immunity against BVDV and other viral agents that make the susceptible animal development of PI calves.
Please call or email if you have any questions.
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