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June 2011 Archive for Dairy Today Healthline

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Dairy Today Healthline

Including Hardjo-Bovis in Calf Vaccination Program May Reduce Chronically Infected Carriers

Jun 06, 2011

The economic losses associated with Lepto hardjo-bovis disease often go unrecognized or are attributed to other factors. These expenses can have a significant impact on your operation’s profitability.

 
Novartis   Doug Scholz, DVM, director of veterinary services, Novartis Animal HealthBy Doug Scholz, DVM, director of veterinary services, Novartis Animal Health
           
In recent years, veterinarians and producers alike have learned more about Lepto hardjo-bovis(LHB),which has emerged as one of the most costly diseases affecting reproduction. Losses come in many forms: reduced conception and pregnancy rates, embryonic death, infertility, rebreeding, extra days open and decreased milk production.
 
LHB is the most common cause of bovine leptospirosis in the U.S. and once a cow is infected, the disease colonizes in the kidneys and reproductive tract.1 Infected cattle have the potential to shed the pathogen through urine and other bodily fluids for several months—putting other cattle within the herd at a higher risk of exposure and infection.
 
Preventing these chronically infected animals significantly reduces exposure and incidence of the disease within the herd. A study conducted in 2010 by Novartis Animal Health showed that vaccinating calves for LHB at a young age provides a key opportunity to break the disease cycle and reduce the incidence of associated reproduction failures.
 
Study findings demonstrated that starting a vaccination program for LHB in calves as young as four weeks old may significantly reduce the risk of chronically infected animals. The vaccination schedule used in the study also sheds light on how producers can leverage a convenient, safe and highly effective inactivated vaccine as a tool for preventing infected animals that shed the LHB pathogen to other cattle within the herd. 
 
How LHB Steals Profits
 
The economic losses associated with LHB come from many areas. Although they often go unrecognized or attributed to other factors, these expenses can have a significant impact on your operation’s profitability:
 
·         Extra days open – Cost estimates range from $1 to $5 per day open, according to dairy reproductive specialists, with most experts settling around $3.2 Miss the heat cycle, and you’ve extended the calving interval by 21 days. Multiply 21 days by $3 per day and that equates to $63 for just one dairy cow.
 
·         Infertility, embryonic death and rebreeding – LHBis also associated with reduced conception rates. In a study that looked at fertility data from 673 cows in five dairy herds, the overall pregnancy rate of seronegative cows was 28% higher than that of cows with an MAT greater than 1:100 for LHB.3 Plus, an early pregnancy loss that causes an increase of 45 days open can result in lost profits between $90 and $225.4
 
·         Reduced milk production – Cows that have poor conception rates may not produce enough milk in late lactation to remain profitable. A Canadian study found a mean reduction in net revenue of approximately $4 per cow from a one-day increase in the adjusted calving interval.5
 
·         Culled cow expenses – Selling open cows means incurring the cost of raising or purchasing replacement animals.
 
LHB Prevention Strategies
 
Identification and diagnosis of LHB is more difficult than other diseases because cattle are “maintenance” hosts. This means infected cattle may have no outward signs and will produce low antibody titers. So, unlike diseases in which cattle are “incidental” hosts, which result in highly apparent symptoms and antibody titers, LHB is subtle, almost covert. 
 
As a result, reproductive problems associated with LHB are frequently attributed to insemination protocol problems, human error or other issues. And too often the true cause goes unidentified and reproduction programs sputter.
 
Controlling LHB requires a combination of biosecurity, antibiotics, vaccination and culling. Start by eliminating carriers through antibiotic treatment, combined with a vaccination program to help prevent new infections. When selecting a lepto vaccine, make sure that it contains a Lepto hardjo-bovisisolate that originates from the U. S. and provides a 12-month duration of immunity.
 
It’s important to work closely with your veterinarian, because in most cases it will be more cost effective to treat and/or vaccinate for the disease instead of testing. Testing can cost as much as $50 per cow, whereas vaccines that contain the specific hardjo-bovisantigens average $2­ to $3 per head.
 
Start a vaccination program when calves are as young as four weeks old to reduce the risk of those animals becoming carriers. If you cannot vaccinate the entire herd start with replacement heifers, which generally are more severely affected by reproductive diseases.
 
For more information, contact a Novartis Animal Health representative or visit www.livestock.novartis.com.
 
References
1.       Zuerner RL, et al. Repetitive Sequence Element Cloned from Leptospira interrogans Serovar Hardjo Type Hardjo-Bovis Provides a Sensitive Diagnostic Probe for Bovine Leptospirosis. J Clin Microbiol 1988;26:2495-2500.
2.       De Vries, A. Determinants of the cost of days open in dairy cattle. Department of Animal Sciences, University of Florida, Available at http://www.animal.ufl.edu/devries/publications/2006/isv_11_1114.pdf. Accessed 5/25/11.
3.        Dhaliwal GS, Murray RD, Dobson H, Montgomery J, Ellis WA. Reduced conception rates in dairy cattle associated with serological evidence of Leptospira interrogans serovar hardjo infection. The Veterinary Record. 1996;139:110-114.
4.       Kirk, J. Infectious abortions in dairy cows. University of California-Davis. Available at: http://www.vetmed.ucdavis.edu/vetext/inf-da/abortion html. Accessed: 12/20/05.
5.     Plaizier JCB, King GJ, Dekkers , JCM, Lissemore K. Estimation of economic values of indices for reproductive performance in dairy herds using computer simulation. J Dairy Sci. 1997;80:2775-2783.
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