Fresh cow surveillance
December 01 2021
Author: Roger L. Saltman, DVM, MBA

The main goal of commercial dairy farms is to maximize economic returns by optimizing milk production and minimizing expenses. Both clinical and subclinical mastitis reduce milk production and increase cost, and mastitis remains the costliest disease in U.S. dairy cattle. One recent study estimated that the cost of just subclinical mastitis in the U.S. dairy industry exceeds $1 billion annually. That study suggested the overall production loss for the average U.S. dairy farm was estimated at $110 per cow annually.

Mastitis is caused by pathogens getting through the teat canal and entering the udder tissue. Many new infections occur during the late dry period or shortly after calving. Intramammary infection (IMI) during this period around calving increases the risk of clinical mastitis (CM) in the early subsequent lactation. Even in the best managed herds, 4–6% of quarters show inflammation at calvingii. Treatment of IMI during the immediate postpartum period can lead to reduced BMSCCiii which, in turn, can provide the dairy with additional quality milk premiums. Eliminating IMI in early lactation may also have significant economic benefits by decreasing the impact on the animal’s peak milk production potential, may decrease the amount of discarded milk associated with treatment, and improve reproductioniv.

On-farm or in-clinic PCR testing is now available to detect the presence of specific DNA markers for mastitis pathogens like Prototheca, Mycoplasma, Strep and Staph. These tests provide same day (about three hours) results and offer cost savings since samples can be pooled from up to five cows. A typical Fresh Cow Mastitis Surveillance Program using this technology would be as follows:
  • Once a week on a given day, all animals fresh 4 to 10 days (inclusive) will have a composite sample taken of milk from all 4 quarters (using a Teat End Prep and Milk Sampling Protocol developed by the herd’s veterinarian or the NMC). A “pooled sample” for PCR testing is then created by taking equal amounts of the individual cows’ composite samples. The original composite samples will be immediately refrigerated in case they need to be tested later.
  • The 5-cow “pooled samples” will be tested for the presence of genetic material from Mycoplasma species and Prototheca species using the Acumen Detection MYPRO™ reagent. Additionally, these samples may be tested for the presence of genetic material from Staph aureus and Strep uberis using the Acumen Detection SASUB™ reagent.
  • If a 5-cow pooled sample tests positive for any of the pathogens, all of the 5 cows will have their composite samples removed from the refrigerator for individual testing using the MYPRO reagent and/or the SASUB reagent.
  • Protocols for cows that test positive for Mycoplasma or Prototheca should be developed with the help of the herd’s veterinarian. One approach would be to immediately move the positive animals to a separate pen that is milked last. The specific farm protocol should also consider:
    • If there is a desire to cull these animals as soon as practicable, a follow-up confirmatory composite sample from the individual cow should be tested again using the Acumen reagent or a complete DNA test from an outside laboratory.
    • Alternatively, the screened positive animal can continue to be milked in the “chronic pen” and, if she becomes clinical, can be immediately culled.
    • Additional protocols can be developed with help of the herd’s veterinarian.
  • Protocols for cows that test positive for Staph aureus or Strep uberis should be developed with the help of the herd’s veterinarian. If these infections are detected early, published researchvv,vi has shown that many of these infections can be cured. According to this research, the best approach for treating Staph aureus is a daily dose of Pirsue® (pirlimycin) for 8 days. Similarly the best approach for treating Strep uberis is a daily dose of Spectramast LC® (ceftiofur) for 8 days. Appropriate withhold times for milk and meat should be determined with the assistance of the local veterinarian.