Biosecurity Principles as Applied to Udder Health

William M. Sischo Pennsylvania State University University Park, Pennsylvania
Think of the last time you bought a car or truck, particular a “previously owned” vehicle. When you started shopping you likely had an idea of the model and age of the vehicle, some of the specifications (e.g. engine size, transmission and drive train), mileage on the vehicle, and your price range. You might have worked with a used car dealer or maybe through private owners, either way you made phone calls, screened some vehicles out, made visits to homes or car lots, and looked at the cars. First impressions were important but you didn’t stop there, you kicked a few tires, sat in the driver’s seat, took the vehicle out for a drive, looked under the hood, checked for oil leaks, looked for unusual tire wear, you might have asked for service records, crawled under the vehicle, and checked to see if there was a spare tire. You might have taken the vehicle to your mechanic and had them look it over. You probably took it out for a drive a couple of times before you finally laid out some cash to purchase the vehicle. You expect your newly purchased vehicle will be reliable, safe, and perform to your satisfaction and since you spent some time during the purchase process you are likely to end up with a vehicle that meets your expectations.

Now reflect on how you last purchased cows or heifers as herd replacements or additions. Typically cows are purchased through sales yards and purchasing agents. Often the buyer doesn’t know anything about the cow or heifer’s background nor about the farm of origin. Even if the farm is known there is little effort to find out why the animal is being sold or anything about the farm’s health history. You see her, you buy her, and you bring her home. You expect that your newly purchased cow or heifer will be reliable and perform to your expectations. But if you know so little about the animal’s background, you’ll be lucky if she meets your expectations and doesn’t bring health problems to your herd.

Case 1: The Growing Fast Herd

Jane and John woke up one fine summer day, looked out at their 300-cow herd and their three sons home from college, and knew that the farm enterprise would be too small for them to keep the family together. The next week they talked with their banker about expansion of their dairy to 1200 milking cows. Twelve months later they were in new facilities and waiting for new cows to arrive. They bought out three herds in their area and worked with a cattle dealer to purchase another 600 cows consolidated from a variety of sources. The optimism of the expansion disappeared as the second group of cows arrived with pneumonia. The pneumonia spread as more animals arrived. Fifteen percent of the new cows died or were culled because of respiratory disease. The pneumonia outbreak subsided, the cows were moved into the new facilities and then the real problems began. Although they had hired and trained new milkers, the management was not quite up to the task of supervising the crews. Milking time procedures slipped, bulk tank somatic cell count began to rise, and clinical mastitis increased. A bulk tank culture revealed mycoplasma. As a result of the mastitis 200 cows were culled. In all the planning for expansion, biosecurity was forgotten.

Case 2: Buy ‘em and ship ‘em

Rick has always enjoyed buying and selling cows. When his father was still running the farm they kept the herd closed, except for the occasional purchase from a neighbor or a friend. Rick has pretty much kept the same policy. Over the last year he has purchased a few animals from the sales yard, he fancy’s he has a good eye for stock and can spot a bargain. The farm has had the same milking procedures for 10 years but the somatic cell count is moving up. The number of chronic high somatic cell count cows has increased. Rick’s veterinarian cultured most of the high cell count cows and found a high prevalence of Staphylooccus aureus. The last two cows that Rick purchased were on the high somatic cell count list.

Biosecurity and Purchasing Cows

There are many reasons to buy cows. It’s necessary to purchase cows as part of herd expansions and sometimes herd removal policies dictate that new animals must be brought into the dairy herd to maintain cow numbers but as you buy remember the saying, Caveat emptor* “buyer beware.” People don’t sell their best cows, herds don’t disperse because of success, and cows like routine. The stress of moving and new environments make new arrivals to your herd more likely to shed disease organisms and become sick. You need to protect your investment in cows, your farm enterprise, and importantly, maintain your herd’s udder health by developing a sound biosecurity program for your farm.

Biosecurity Practices For Udder Health -- Know the Farm of Origin

Request a bulk tank culture from the farm of origin - You want to prevent the introduction of mastitis pathogens such as Streptococcus agalactiae, Staphylococcus aureus, Corynebacterium bovis, and Mycoplasma sp. A bulk tank milk culture should be part of your pre-purchase examination to screen for these pathogens.
Request to see 6 to 12 months of bulk tank somatic cell count data - These data will give you a sense of recent trends in the herd’s udder health program. Upward trends in somatic cell count or even consistent SCC levels above your standards should send you cautionary signals.
Request to see 6 to 12 months of bulk tank bacteria counts (SPC) - While these data may not be related to herd udder health, they do suggest a level of management. Again, upward trends or bacteria counts that are higher than your current standards may suggest that you look elsewhere for your new herd additions.
Request to see 6 to 12 months of records for clinical mastitis - This information will allow you to evaluate trends in clinical mastitis in the herd and give you a different perspective on udder health in the herd than bulk tank SCC. Levels of clinical mastitis higher than you are experiencing in your herd again suggest a level of management different than your expectations.

Biosecurity Practices For Udder Health -- Know the Cows

If you are purchasing single animals or small groups of cows, it is important to have some pre-purchase procedures.

Request a somatic cell count and clinical mastitis history for each cow to be purchased. Cows with high SCC or history of chronic or repeat episodes of clinical mastitis should be rejected.
Request the results of quarter milk samples from each cow to be purchased. These are simple, relatively inexpensive, and well worth the investment of time and money. Reject cows with evidence of bacterial infections.
Conduct a physical examination on all cows to be purchased. This includes a thorough examination of the udder, milk quality, and teat ends. Reject cows that don’t meet your standards for conformation.

Biosecurity Practices For Udder Health -- Protect Your Herd

Although the ideal practice is to have pre-purchase screening protocols and reject animals and groups of animals that do not meet your standards, reality is that many animals are purchased without any knowledge of their health history nor the farm of origin. This means that every purchased animal is a threat to the health of your herd. Even if you have pre-screened animals you must still treat all purchased animals as potential health risks to your herd. On-farm biosecurity is a combination of management techniques and facility management.

Newly purchased animals should be housed in separate or isolated facilities from the herd. This is a good practice for overall biosecurity and will help you manage these animals as a separate milking group. The length of time to maintain this separation depends on your goals, but discuss this with your veterinarian.
Collect and culture quarter milk samples to check for infection. If cows are infected consult with your veterinarian on management and treatment options.
Assume that any cow you purchase has been recently treated with antibiotics. Although this is not a health issue it is a milk quality issue that is a threat to your milk market. Evaluate the milk from all purchased cows for the presence of antibiotics before you include her milk in the bulk tank.
Milk all purchased cows last or with separate milking equipment. This should be standard procedure until you and your veterinarian give these new cows a clean bill of health.

Developing and following good biosecurity plans takes time and planning, but the cost to the farm enterprise for not having these plans can be considerable. If you expect that purchasing cows and heifers will enhance and not damage your herd then planning before the purchase will be well worth the efforts. It is also important to remember that developing biosecurity plans decreases your risk of introducing health problems to your herd, but there is no guarantee that it will completely prevent the introduction of disease to your herd. Monitoring bulk tank SCC and bacteria, individual cow SCC, and clinical mastitis rates are ongoing tasks and essential for maintaining high levels of herd health and milk quality.

Presented at the 1997 National Mastitis Council Annual Meeting; Published in the 1997 National Mastitis Council ANnual Meeting Proceedings, pg. 124.

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