Train wrecks” involving infectious disease and mastitis can and do occur in expansion herds. While some would speculate that the wrecks only occur in herds that buy cattle of unknown origin, the truth is otherwise. Every farm faces an element of risk during expansion.

Take, for example, one Midwestern dairy that maintained a closed herd for nearly 15 years and grew cow numbers steadily in preparation for an expansion. When a neighbor had a production sale, the dairy purchased several heifers. The heifers were penned separately, but nearby home-grown heifers became sick. Blood-testing yielded surprising results. The newly-purchased animals received a clean bill of health, but persistently-infected bovine viral diarrhea (BVD) animals were found in the home herd.

The stress of the expansion triggered shedding in these persistently-infected animals, explains Marj Faust, extension dairy specialist at Iowa State University. Although the herd had always been well-managed, the additional stress, combined with an unknown lapse in the dairy’s vaccination schedule, led to the BVD outbreak.

Whether you are a closed herd growing from within, buying heifers, or buying cows, you’re vulnerable to health problems during an expansion, says Faust. Cows are typically 30 percent to 40 percent of the cost of an expansion, excluding land, yet pay the bill for the entire project. That means you must protect their health for a successful expansion.

Keep your focus
Most dairy producers undertake just one major expansion in their careers, so they want to do everything just right. But focusing on the facilities — at the possible exclusion of animal health — can lead to unexpected problems.

This was borne out in a research study that Faust conducted with approximately 20 expansion herds in the Midwest. In-depth personal interviews revealed that every dairy experienced some breach in biosecurity during its expansion. BVD, infectious bovine rhinotracheitis (IBR) in heifers, foot warts, and Staph aureus mastitis were just a few of the problems, says Faust. Here’s a few of the findings from her research:

  • 58.8 percent of producers purchased animals from unknown sources.
  • 47.1 percent of producers tested milk samples for mastitis pathogens before buying animals.
  • Half of the herds indicated that BVD and hairy foot warts were significant disease problems during expansion.
  • 31 percent of herds treated or removed animals for Johne’s disease.
  • Nearly 20 percent of herds had losses from IBR and Clostridium.
  • Dairy producers identified lame cows as a primary culling decision.
  • Based on her research findings, and computer simulations, producers can expect a cull rate of 25 percent the first year, and then return to their pre-expansion cull rate, on average 35 percent.

In addition to Faust’s research, the “1999 Wisconsin Dairy Modernization Project” conducted by Roger Palmer, dairy systems management specialist at the University of Wisconsin, showed similar biosecurity results in 302 herds that increased herd size by at least 40 percent. Here’s how the farms responded when asked what biosecurity measures they had taken to prevent disease introductions from purchased animals:

  • 91 percent visually inspected animals before purchase.
  • 67 percent increased the level of vaccination in the existing herd.
  • 49 percent vaccinated incoming cattle before moving them.
  • 51 percent vaccinated incoming cattle after moving them.
  • 42 percent examined individual somatic cell count records.
  • 27 percent isolated animals after moving them.
  • 26 percent examined individual cow records.
  • 21 percent blood-tested animals before purchase.
  • 15 percent did bulk tank cultures before purchase.

These numbers show tremendous room for improvement. Most expansions can handle a small biosecurity breach. But it only takes one big problem to undermine the profitability of your project. However, most can be prevented.

To assist you in avoiding health problems during expansion, this special health issue of Dairy Herd Management offers ideas on preventing disease entry, avoiding lameness, and strategies for culturing arriving animals for mastitis. Review these articles with your veterinarian as you plan your expansion.