Photo credit: Mauricio Rosales
The majority of dairy farms in the U.S. utilize blanket dry cow therapy (BDCT) to dry off cows. This practice of treating every cow was adopted to decrease mammary infections during the dry period and to prevent new infections in the upcoming lactation. However, public health concerns about overuse of antibiotics are forcing the industry to look at alternative management strategies.
Selective dry cow therapy (SDCT) has been raised as an option to decrease the use of antibiotics in food animals and the resistance to antimicrobials. Adopting SDCT is an integral approach that determines the utilization of antibiotics based on the infection status of each quarter and somatic cell count (SCC) records. Studies have found that SDCT is as successful as BDCT in the prevention and treatment of intramammary infections during the dry period and can reduce the use of antimicrobials by 21% (Østeras et al., 1999; Cameron et al., 2014).
Although this alternative looks like an attractive solution, it demands a lot of patience and commitment. For instance, finding an effective method to identify subclinically infected cows could be a challenge. On many farms, the California Mastitis Test (CMT) is the standard procedure to identify cows with mammary infections. While this is a good tool for clinical cases, it may not be the most precise way to identify subclinical infections. Studies have found that the CMT only has 70% sensitivity (Middleton et al., 2004). This means that in many cases, some cows will be misdiagnosed. This certainly will affect the outcome of the SDCT program.
Another option to identify intramammary infections is on-farm culture. This is a more sensitive test that can not only provide the infectious status of a cow but can also identify the causative agent. Studies have concluded that adding bacteriological information to the decision making process can significantly increase the success of a SDCT program (Østeras et al., 1999). This is relatively inexpensive technology that can highly benefit the SDTC program and overall udder health monitoring.
Individual SCC data and clinical mastitis incidence records are also important parts of a well-managed SDCT strategy. These data will help producers decide which cows and what quarters need treatment.
Not all farms are in conditions to adopt SDCT. If your bulk tank milk SCC is higher than 200,000 cells/mL, you should first work on decreasing that number before moving to a SDCT program. Optimizing treatment and cleanliness will help you reach a lower SCC. Talk with your veterinarian about udder health and put together a plan to achieve a lower overall herd SCC. Alternatively, if you have a low SCC (less than 150,000 cells/mL), you might need a higher specificity test, such as polymerase chain reaction (PCR), to identify pathogens affecting your herd. This test will identify DNA sequences that are specific for each microorganism. By identifying the right type of bacteria affecting your cows, more precise and effective treatment protocols can be applied.
Additionally, the utilization of a teat sealant (TS) in all 4 quarters is highly recommended to achieve good results in your SDCT program (Berry and Hillerton, 2002; Rabiee and Lean, 2013). A new study that evaluated 16 herds with a total of 729 cows with low SCC (< 200,000 cells/mL) found no differences in the prevalence of intramammary infections after calving for cows treated with BDCT TS only, or with TS plus dry cow antibiotic (DCT) (Figure 1; Cameron et al., 2016). These results indicate that TS play a key role in the success of a SDCT program.
Figure 1. Prevalence of intramammary infection within 18 d after calving in quarters receiving blanket dry cow therapy (BDCT) plus internal teat sealant (TS) and quarters selectively treated based on on-farm culture results with dry cow antibiotic (DCT) plus TS, or TS alone. No significant differences found between treatments. Adapted from Cameron et al., 2014.
Keep in mind that when applying teat sealants or antimicrobials, the infusions have to be done in an aseptic manner to avoid risk of infection.
Implementing all these protocols might be one of the most difficult challenges that dairy farmers have to face when considering a SDCT. However, many European countries have successfully adopted SDCT since the preventive use of antimicrobials in those countries has been banned. In a study conducted in the Netherlands in 2013, researchers found that SDCT was effectively adopted by 75% of Dutch famers (Scherpenzeel et al., 2016). The main criteria to select cows for dry cow treatment was SCC history. This study demonstrates that with correct guidance, new programs, such as SDCT, can be implemented with success.
More and more we are seeing consumers demanding food production systems free of antibiotics. As part of this evolving community, we should be able to adapt to those requirements. Choosing SDCT can be a reliable option that needs serious consideration if we want to decrease the use of antimicrobials. European countries have shown that this is possible without compromising the cow’s health. We need to be proactive and implement SDCT programs that fit the conditions and resources of our farms if we want to keep up with the market’s demands.
- Berry, E. A., and J. E. Hillerton. 2002. The effect of an intramammary teat seal on new intramammary infections. J. Dairy Sci. 85:2512-2520.
- Cameron, M., S. L. McKenna, K. A. MacDonald, I. R. Dohoo, J. P. Roy, and G. P. Keefe. 2014. Evaluations of selective dry cow treatment following on-farm culture: Risk of post calving intramammary infection and clinical mastitis in the subsequent lactation. J. Dairy Sci. 97:270-284.
- Huxley, J. N., M. J. Green, L. E. Green, and A. J. Bradley. 2002. Evaluation of the efficacy of an internal teat sealer during the dry period. J. Dairy Sci. 85:551-561.
- Middleton, J. R., D. Hardin, B. Steevens, R. Randle, and J. W. Tyler. 2004. Use of somatic cell counts and California mastitis test from individual quarter milk samples to detect subclinical intramammary infections in dairy cattle from a herd with a high bulk tank somatic cell count. J. Am. Vet. Med. Assn. 224:419-423.
- Østeras, O., V. L. Edge, and S. W. Martin. 1999. Determinants of success or failure in the elimination of major mastitis pathogens in selective dry cow therapy. J. Dairy Sci. 82:1221-1231.
- Rabiee, A. R., and I. J. Lean. 2013. The effect of internal teat sealant products (Teatseal and Orbeseal) on intramammary infection, clinical mastitis, and somatic cell counts in lactating dairy cows: A meta-analysis. J. Dairy Sci. 96:6915-6931.
- Scherpenzeel, C. G. M., S. H. W. Tijs, I. E. M. den Uijl, I. M. G. A. Santaman-Berends, A. G. J. Velthuis, and T. J. G. M. Lam. 2016. Farmers’ attitude toward the introduction of selective dry cow therapy. J. Dairy Sci. 99:8259-8266.