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Kansas State University

 

Beef Research News
Brought to you by Kansas State University College of Veterinary Medicine - Farm Animal Section
January 2009

 

 

 

Contents:

Evaluation of feedlot economic and health impacts after exposure to BVD PI cattle

Genetic characterization of BVD from PI calves based on dam vaccination status

Behavior of feedlot cattle and interaction with manila ropes

Plasma metabolites at arrival and relationship with BRD, ADG, and Carcass Characteristics

 



Evaluation of feedlot economic and health impacts after exposure to BVD PI cattle

The objective of this research was to evaluate economic effects and health and performance of the general cattle population after exposure to cattle persistently infected (PI) with bovine viral diarrhea virus (BVDV) in a feedlot. Study was conducted using 21,743 high-risk calves from the southeastern United States. PI status was determined by use of an antigen-capture ELISA (ACE) and confirmed by use of a second ACE, reverse transcriptase–PCR assay of sera, immunohistochemical analysis, and virus isolation from sera. Groups with various amounts of exposure to BVDV PI cattle were used. After being placed in the feedlot, identified PI cattle were removed from 1 section, but PI cattle remained in another section of the feedlot. Exposure groups for cattle lots arriving without PI animals were determined by spatial association to cattle lots, with PI animals remaining or removed from the lot. 15,348 cattle maintained their exposure group. Performance outcomes improved slightly among the 5 exposure groups as the risk for exposure to BVDV PI cattle decreased. Health outcomes had an association with exposure risk that depended on the exposure group. Comparing cattle lots with direct exposure with those without direct exposure revealed significant improvements in all performance outcomes and in first relapse percentage and mortality percentage in the health outcomes. Economic analysis revealed that fatalities accounted for losses of $5.26/animal and performance losses were $88.26/animal. This study provided evidence that exposure of the general population of feedlot cattle to BVDV PI animals resulted in substantial costs attributable to negative effects on performance and increased fatalities.

Hessman, B.E., R.W. Fulton, D. B. Sjeklocha, T.A. Murphy, J.F. Ridpath, and M.E. Payton. 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. Amer J Vet Res. 2009 70(1): 73-85.


Genetic characterization of BVD from PI calves based on dam vaccination status

The objective of this research was to collect and partially characterize strains of bovine viral diarrhea viruses(BVDVs) isolated from persistently infected (PI) calves born to vaccinated dams, determine genetic diversity of the isolated viruses, and identify regional distribution of genetically similar virus subpopulations. Research was conducted using 17 noncytopathic (NCP) BVDVs from PI calves from 11 herds of beef or dairy cattle. Viral RNA was extracted from infected cell cultures, and BVDV-specific PCR primers were used to amplify > 1,000 bases of the viral genome. Derived sequences were used for molecular phylogenetic analyses to determine the viral genotype and viral genogroup and to assess genetic similarity among BVDVs. Analysis of the 17 NCP strains of BVDV failed to detect a viral genotype or viral genogroup not already reported to exist in the United States. One virus was classified as genotype 1, genogroup 1b, and 16 viruses were classified as genotype 2, genogroup 2a. Genotype 2 strains were genetically diverse, and genetic similarities were not obvious among viruses from geographic regions larger than a small locale. Viruses isolated from herds where a genotype 1, genogroup 1a BVDV vaccine was administered prior to breeding were primarily genetically diverse genotype 2, genogroup 2a BVDVs. Vaccination with multiple BVDV genotypes may be needed to improve protection. Methods used in this study to obtain and analyze field strains are applicable to assessing efficacy of current BVDV vaccines. Candidates for future vaccines are viruses that appear able to elude the immune response of cattle vaccinated against BVDV with existing vaccines.

Bolin, S.R., A. Lim, D.M. Grotelueschen, W.W. McBeth, and V. S. Cortese. Genetic characterization of bovine viral diarrhea viruses isolated from persistently infected calves born to dams vaccinated against bovine viral diarrhea virus before breeding. Amer J Vet Res. 2009 70(1): 86-91


Behavior of feedlot cattle and interaction with manila ropes
Providing cattle with access to manila ropes has shown promise as a means of monitoring zoonotic bacteria in pens of feedlot cattle. Studies were conducted to determine the impacts of climate, animal age and BW, number of ropes, duration of placement, and previous rope access on efficacy of ropes as a sampling technique for feedlot cattle. Eight pens of commercial finishing cattle (average 196 ± 19 animals per pen, 536.7 ± 22.9 kg) were monitored for a total of 7 d in October of 2003 (commercial study). One rope was tied on the pen railing adjacent to the feed bunk in each pen, and the proportion of animals within the pen contacting the rope was recorded. In a second study, 80 cattle housed in 8 pens (each 270 m2; 10 animals/pen) were monitored for 1 d/wk using video cameras (video study). Video images were collected for 8 consecutive weeks immediately after weaning (average BW = 252.7 ± 30.6 kg) and for 6 wk at the end of the finishing period (average BW 541.2 ± 42.8 kg). In the commercial study, the proportion of cattle contacting the rope per pen increased over the first 6 h to 70% (P < 0.05), although approximately 50% of the cattle contacted the rope within 2 h after placement. A 40°C reduction in ambient temperature on d 6 caused cattle to cease contact with the ropes, although after 6 d of acclimation to reduced ambient temperature, interactions with ropes recovered to 47% of previous values. In the video study, weaned calves required 2 wk of acclimation to the feedlot environment before contact with the rope was maximized. Contact with the rope was most frequent 3 to 8 wk after entry into the feedlot and decreased (P < 0.05) as cattle approached slaughter weight. It is likely that ropes will be most effective at monitoring zoonotic bacteria in pens of cattle during the mid-feeding period where the pen environment is stable and cattle are inquisitive but not highly reactive.


K. Stanford, R. Silasi, T. A. McAllister, and K. S. Schwartzkopf-Genswein.
Behavior of feedlot cattle affects voluntary oral and physical interactions with manila ropes. 2009 J. Anim Sci. 2009. 87:296-303.



Plasmametabolites at arrival and relationship with BRD, ADG, and Carcass Characteristics

Six hundred sixty-five crossbred beef heifers initially weighing 225 kg were used in a completely randomized design to measure plasma glucose, lactate, and urea N concentrations at time of initial processing, determine the incidence of apparent bovine respiratory disease (BRD) in receiving cattle, and evaluate the effect of apparent BRD on subsequent cattle growth and carcass characteristics. Heifers were processed within 24 h of arrival, and processing included vaccination against common viral and clostridial diseases, recording rectal temperature, and sampling whole blood for subsequent measurement of plasma glucose, lactate, and urea concentrations. Heifers were monitored for clinical signs of apparent BRD, including depression, lethargy, anorexia, coughing, rapid breathing, and nasal or ocular discharge. Heifers exhibiting signs of apparent BRD received antibiotic therapy, and the number of times a heifer was treated for apparent BRD was recorded. Following the 36-d receiving period, heifers were transported to native grass pastures and allowed to graze for 136 d. At the end of the grazing season, heifers were transported to a commercial feedlot where they were adapted to a common finishing diet offered for ad libitum consumption. Following the 124-d finishing period, heifers were slaughtered and carcass data were collected. Heifers treated for apparent BRD had decreased plasma glucose (linear, P < 0.01), lactate (linear, P < 0.01), and urea N concentrations (linear, P < 0.06) measured at time of initial processing. Rectal temperature measured at time of initial processing tended to be greater (linear, P < 0.11) for heifers treated for apparent BRD. Heifers treated for apparent BRD during the receiving period had decreased overall ADG (linear, P < 0.10), final BW (linear, P < 0.01), HCW (linear, P < 0.01), fat thickness (linear, P < 0.01), and marbling score (linear, P < 0.03). These data suggest that initial plasma glucose and lactate concentrations might be affected by the health status of receiving cattle and that increased incidence of apparent BRD in cattle decreases ADG and carcass quality.



Montgomery, S.P., J. J. Sindt, M. A. Greenquist, W. F. Miller, J. N. Pike, E. R. Loe, M. J. Sulpizio and J. S. Drouillard. Plasma metabolites of receiving heifers and the relationship between apparent bovine respiratory disease, body weight gain, and carcass characteristics. 2009 J Anim Sci 87:328-333.


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Brad White
Beef Production Medicine
Q211 Mosier Hall
Manhattan, KS 66506
bwhite@vet.ksu.edu