Progress 06/01/05 to 12/31/08
Outputs
OUTPUTS: Total dry cow therapy, DCT (treatment of all quarters of all cows with antibiotics at dry-off) has been an essential component of mastitis control programs in the US dairy herds for decades. Due to concerns over development of antimicrobial resistance and claims about overuse of antibiotics in animal agriculture, selective DCT (SDCT) has received more attention in recent years. The current study was designed to evaluate whether selective treatment of cows at dry-off can maintain udder health in US dairy herds. The study was conducted in four Ohio dairy herds. Cows in these herds were classified as "high SCC" and "low SCC" cows based on their somatic cell counts and clinical mastitis history during the current lactation preceding the dry-off. "High SCC" cows were assumed to be infected and they all were treated with intramammary antibiotics after the last milking at dry-off. "Low SCC cows" were assumed to be healthy/uninfected and they were randomly assigned to receive or not to receive antibiotic intramammary treatment at dry-off. Milk samples were collected from cows at dry-off and at calving and from clinical mastitis cases during the dry period or the following lactation. Milk yield and somatic cell count of the enrolled cows were followed during the subsequent lactation. Implementation of SDCT requires a quick and cost-effective on-farm method for identifying cows for treatment and cows that can be left without treatment. The results of this study indicate that cows can be accurately identified for dry cow treatment (or for no treatment) based on their somatic cells counts at the end of lactation and clinical mastitis history during the lactation (Torres et al 2008, J. Dairy Res.). Additionally, the results indicated the agreement between the first and the second sample of a duplicate pair (which is often recommended for research purposes) was high when criteria to call a sample positive is adjusted for the number of CFU/ml of milk by considering the epidemiology of different mastitis organisms. This finding suggests that an IMI can be accurately diagnosed with single samples, which is an important and practical finding when conducting large field studies (Torres et al 2008, JDVI). Most interestingly, milk yield of untreated and treated low-SCC cows at dry-off did not differ significantly during the following lactation. On average, treated low-SCC cows had lower SCC (approximately 35000 cells/ml) than the untreated cows during the following lactation, however, the effect was variable between different herds (Rajala-Schultz et al 2011, J. Dairy Res.). Thus, a uniform recommendation to routinely dry-treat all cows in all herds or to advise all herds to adopt selective dry-treatment of infected cows only is not warranted: Advice regarding dry cow therapy should thus be herd-specific. Additionally, results from the study suggest that antibiotic usage, in the form of dry cow therapy and lactational mastitis treatments create selection pressure and can increase the prevalence of antibiotic resistant bacteria (Rajala-Schultz et al. 2008, Vet. Micro). PARTICIPANTS: Not relevant to this project. TARGET AUDIENCES: Not relevant to this project. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
The results of this study have immediate utility to the dairy industry and dairy producers. This research is significant, because the new resulting knowledge suggests that the selective dry cow therapy (SDCT) can maintain milk quality and milk production level in US dairies. The impact of dry treatment, or the lack thereof, however, varied considerably between herds. The results suggested that in some herds treating all cows at dry-off may be beneficial while in other herds leaving healthy cows without antibiotic dry cow treatment has no negative impact on milk yield or milk quality (SCC) and in fact, may be beneficial. Therefore, recommendations regarding DCT should be herd-specific to optimize the overall benefits from the treatments. Implementation of SDCT can reduce antibiotic selection pressure and consequently, the development of antibiotic resistant bacteria, ensuring the efficacy of our current treatments to the future. Also, implementing selective treatment of cows could improve profitability of dairy operations by reducing treatment costs at dry-off.
Publications
- Torres, A.H., Rajala-Schultz, P.J. 2010: Selective dry cow therapy and somatic cell count on the subsequent lactation. The 5th IDF (International Dairy Federation) Mastitis Conference, 21-24 March 2010, Christchurch, New Zealand, p. 734
- Torres A.H., Rajala-Schultz, P.J., F., DeGraves, F.J. 2009: Milk yield on the subsequent lactation following selective treatment of cows at dry-off. Proceedings of the National Mastitis Council 48th Annual Meeting, Charlotte, NC, Jan. 25-28, 2009.
- Torres A.H., Rajala-Schultz, P.J., Silveira, F., DeGraves, F.J. 2008. Clinical mastitis and selective dry cow therapy. Proceedings of the National Mastitis Council 47th Annual Meeting, New Orleans, Louisiana, Jan. 20-23, 2008, p. 160-161.
- Torres A.H., Rajala-Schultz, P.J., Silveira, F., DeGraves, F.J. 2008. Diagnosis of intramammary infection based on sampling strategy, epidemiology of pathogens and agreement beyond chance. Proceedings of the National Mastitis Council 47th Annual Meeting, New Orleans, Louisiana, Jan. 20-23, 2008, p.190-191
- Rajala-Schultz, P.J., Torres A.H., DeGraves, F.J. 2008: The effect of selective dry cow therapy on subsequent lactation milk yield. 2008 AABP Annual Conference, Charlotte, NC, September 2008.
- Torres A.H., Rajala-Schultz, P.J., DeGraves, F.J. 2008. Milk yield in the consequent lactation after selective treatment of cows at dry-off. Mastitis Control-from science to practice. Proceeding of International Conference, The Hague, The Netherlands, Sept. 30-Oct 2, 2008, p. 442.
- Rajala-Schultz, P.J., Torres A.H., DeGraves, F.J., Gebreyes, W.A. 2007: Antimicrobial resistance and strain persistence of coagulase-negative staphylococci over the dry period. Heifer Mastitis Conference, June 24-26, 2007, Ghent, Belgium
- Rajala-Schultz, P.J., Torres, A.H., DeGraves, J.F. 2011: Milk yield and somatic cell count during the following lactation after selective treatment of cows at dry-off J. Dairy Res. 78 489 to 499
- Torres, A.H., Rajala-Schultz, P.J., DeGraves, F.J., 2009: Diagnosis of bovine intramammary infections based on sampling strategy, epidemiology of pathogens and agreement beyond chance. J. Vet. Diag. Invest. 21, 4, 427-36.
- Rajala-Schultz, P.J., Torres, A.H., DeGraves, J.F., Gebreyes, W.A., Patchanee, P. 2009: Antimicrobial resistance and strain persistence of coagulase-negative staphylococci over the dry period. Vet Micro. 134, 55-64.
- Torres, A.H., Rajala-Schultz, P.J., DeGraves, F.J., Hoblet, K.H. 2008: Using dairy herd improvement records and clinical mastitis history to identify subclinical mastitis infections at dry-off. J. Dairy Res. J Dairy Res. 75, 240-7.
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Progress 06/01/07 to 05/31/08
Outputs
OUTPUTS: Total dry cow therapy, DCT (treatment of all quarters of all cows with antibiotics at dry-off) has been an essential component of mastitis control programs in the US dairy herds for decades and is considered a necessity for good udder health in a herd. Due to concerns over development of antimicrobial resistance and claims about overuse of antibiotics in animal agriculture selective DCT has received more attention in recent years. The above study was designed to evaluate whether selective treatment of cows at dry-off can maintain udder health in US dairy herds. The sample collection and the follow-up period has been completed in four Ohio dairy herds that were enrolled in the study. Cows in these herds were classified as "high risk" and "low risk" cows based on their somatic cell counts and clinical mastitis history during the current lactation preceding the dry-off. "High risk" cows were assumed to be infected and they all were treated with intramammary antibiotics after the last milking at dry-off. "Low risk cows" were assumed to be healthy/uninfected and they were randomly assigned to receive or not to receive antibiotic treatment at dry-off. Milk samples were collected from cows at dry-off and at calving and from clinical mastitis cases during the dry period or the following lactation. Prevalence of intramammary infection at calving, incidence of clinical mastitis, milk yield and culling of cows during the following lactation will compared between treated and untreated healthy cows to evaluate the impact of selective treatment on udder health. The results suggest that cows can be accurately identified for dry cow treatment (or for no treatment) based on their somatic cells counts at the end of lactation and clinical mastitis history during the lactation (Torres et al 2008, J. Dairy Res.). The preliminary results also suggest that in some herds, treating presumably uninfected cows at dry-off can be detrimental (e.g., decreases milk yield during the following lactation), whereas in some herds the opposite can be true. Careful consideration of farm characteristics and SCC of cows at the end of lactation is needed to maximize the benefits of dry cow therapy in dairy herds. Thus, recommendations about DCT should be herd specific. Additionally, results suggest that continued antibiotic usage, in the form of dry cow therapy and lactational mastitis treatments create selection pressure and can increase the prevalence of antibiotic resistant bacteria (Rajala-Schultz et al. 2008, Vet. Micro). PARTICIPANTS: Paivi Rajala-Schultz is an associate professor specializing in dairy production medicine and epidemiology of dairy cattle diseases. TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
The results of this study will have immediate utility to the dairy industry and dairy producers. This research is significant, because the new resulting knowledge suggests that the impact of (selective) DCT is not uniform across all herds, recommendations regading DCT should be herd-specific. Specifically, implementing selective treatment of cows in some herds could improve profitability of dairy operations by reducing treatment costs and improving udder health and productivity. It can also reduce antibiotic selection pressure and consequently, the development of antibiotic resistant bacteria, ensuring the efficacy of our current treatments to the future. Additionally, reduced antibiotic usage by dairy producers can improve consumer perceptions of the industry and enhance industry sustainability. It is equally important to know whether and when treatment of all cows is needed to maintain udder health and productivity in the herd.
Publications
- Rajala-Schultz, P.J., Torres, A.H., DeGraves, J.F., Gebreyes, W.A., Patchanee, P. 2008: Antimicrobial resistance and strain persistence of coagulase-negative staphylococci over the dry period. Vet. Micro. doi:10.1016/j.vetmic.2008.09.008 , (in press).
- Torres, A.H., Rajala-Schultz, P.J., DeGraves, F.J., Hoblet, K.H. 2008: Using dairy herd improvement records and clinical mastitis history to identify subclinical mastitis infections at dry-off. J. Dairy Res. J Dairy Res. 75, 240-7.
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Progress 06/01/05 to 06/01/06
Outputs
Total dry cow therapy (treatment of all quarters of all cows with antibiotics at dry-off) has been an essential component of mastitis control programs in the US dairy herds for decades and is considered a necessity for good udder health in a herd. Due to concerns over development of antimicrobial resistance and claims about overuse of antibiotics in animal agriculture selective dry cow therapy has received more attention in recent years. The above study was designed to evaluate whether selective treatment of cows at dry-off can maintain udder health in US dairy herds. The above study and related sample collection are ongoing. Four Ohio dairy herds are enrolled in the study and cows in these herds are classified as "high risk" and "low risk" cows based on their somatic cell counts and clinical mastitis history during the current lactation preceding the dry-off. "High risk" cows are assumed to be infected and they all are treated with intramammary antibiotics after the
last milking at dry-off. "Low risk cows" are assumed to be healthy/uninfected and are randomly assigned to receive or not to receive antibiotic treatment at dry-off. Milk samples are collected from cows at dry-off and at calving and from any clinical mastitis cases during the dry period or the following lactation. Prevalence of intramammary infection at calving, incidence of clinical mastitis, somatic cell counts and culling of cows during the following lactation are compared between treated and untreated healthy cows to evaluate the impact of selective treatment on udder health. It is still too early to present any firm results or conclusions from this study. Up to date, preliminary results have been presented in scientific conferences (see publications).
Impacts
This research is significant, because the new resulting knowledge is expected to demonstrate that antibiotic usage can be reduced without sacrificing udder health, milk quality or herd profitability. The results will have immediate utility to the dairy industry and dairy producers. Specifically, reduced antibiotic use will improve profitability of dairy operations by reducing treatment costs, and will reduce antibiotic selection pressure and consequently, the development of antibiotic resistant bacteria. This will improve consumer acceptance and enhance industry sustainability.
Publications
- Torres, A.H., Rajala-Schultz, P.J., DeGraves, F.J., Hogan, J.S. , Hoblet, K. 2007. Diagnosis of intramammary infections based on sampling strategy, epidemiology of pathogens and agreement beyond chance. Submitted to J. Dairy Science, January, 2007.
- Torres A, Rajala-Schultz P.J., Silveira F., DeGraves F. 2006: Udder Health and Selective Dry Cow Therapy. ISVEE XI, Cairns, Australia, August 2006
- Torres, A.H., Rajala-Schultz, P.J., Silveira, F. 2005. Utility of DHI records and clinical mastitis history in identifying subclinical mastitis infections at dry-off. Proceedings of 4th IDF Mastitis Conference in the Netherlands, June 12-15, 2005, 907.
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