Submitted to: American Journal of Veterinary Research
Publication Type: Peer reviewed journal
Publication Acceptance Date: 5/8/2008
Publication Date: 1/1/2009
Citation: Hessman, B.E., Fulton, R.W., Sjeklocha, D.B., Murphy, T.A., Ridpath, J.F., Payton, M.E. 2009. Evaluation of Economic Effects and the Health and Performance of the General Cattle Population after Exposure to Cattle Persistently Infected with Bovine Viral Diarrhea Virus in a Starter Feedlot. American Journal of Veterinary Research. 70(1):73-85. Interpretive Summary: Bovine viral diarrhea virus (BVDV) infects cattle worldwide resulting in disease in both dairy and beef production units. Frequently BVDV is introduced into a production unit by the entry of an animal persistently infected (PI) with BVDV. PI animals are the result of the infection of a fetus before the maturation of the immune system. This infection results in an animal that produces virus and sheds it to its pen mates throughout its lifetime. It is estimated that between 1 and 4 animals out of every 1000 animals entering feedlots are PI. While this number may not sound high, this rate of PI means that in the average feedlot about 50% of the pens will either have a PI animal in it or be next to a pen with a PI animal in it. This study looked at health and growth records for animals housed in a pen or next to a pen with a PI animal compared to animals that were housed with no contact with a PI animal. It was found that contact with a PI animal, whether contact was the consequence of housing in the same pen or of housing in adjacent pens, resulted in significant economic loss. These losses could be attributed to increased death loss (average cost of $5.26 per head) and decreased growth (average cost of $88.26 per head). Previous studies in feedlots were based on fewer animals and only looked at death loss or costs of treatment of sick animals. This is the first large scale study, done under typical production settings, to examine the impact of BVDV exposure on growth rate. Economic data such as this is important to determining the need and potential benefits of programs designed to limit BVDV infections in the U.S.
Technical Abstract: The objective of this research was to evaluate the effects on health and performance in beef cattle resulting from exposure to bovine viral diarrhea virus (BVDV) persistently infected (PI) animals in a commercial feedlot. The study focused on economic effects associated with PI exposure during the starter phase in the feedlot based on evaluation of mobidity, mortality and rate of gain of 15,348 head enrolled in the study. Animals were auction derived calves from Southeast US origin with an average weight of 233 kg (513 lbs) upon entry into the feedlot. PI status was determined by arrival antigen capture ELISA (ACE) test and confirmed with a second ACE test, reverse transcriptase PCR (RT-PCR) testing on serum, immunohistochemistry (IHC), and virus isolation on serum. The rate of PI animals detection was 0.4%. Five treatment groups of varying levels of BVDV PI exposure were utilized (PI in pen for length of study, PI in pen but removed after 72 hr, no PI in pen but housed next to a pen with a PI in it for length of study, no PI in pen but housed next to a pen with a PI in it for first 72 hrs of study, no PI in pen or adjacent pens). Performance parameters improved across the 5 treatment groups as the risk for BVDV PI exposure decreased. When comparing lots with direct exposure (BVDV PI animal within the lot or adjacent to PI lots) to those without direct exposure to BVDV PI animals, there were statistical improvements in all performance outcomes and in the first relapse rate and percent mortality rate in the health outcomes. Economic analysis showed that mortality losses of $5.26 per head and performance losses of $88.26 were associated with direct exposure to BVDV PI animals. This study provided evidence that exposure of the general population of a feedlot to animals PI with BVDV resulted in substantial costs due to negative effects on mortality and performance in the starter phase of the feedlot.