Dairy Excel/Channel: The good, bad and ugly of cell counts


If anything good comes from several weeks of consistently really cold weather besides a surge in Carhartt sales, somatic cell counts should be lower.

Environmental pathogens lurking in bedding or on other barn surfaces should have frozen to death.

Well, maybe that is wishful thinking, but it was easier to keep bedding clean and dry since urine and manure pretty much freeze dried on contact.

Since the weather is warming up, at least temporarily, time for a quick review of the scourge of cow udders.

Back to basics. Let’s go back to basics.

What is a somatic cell? Somatic cells are actually white blood cells that have entered the udder to fight an infection.

When a report says that an individual cow’s or a herd’s SCC is 100,000, it really means that there are 100,000 somatic cells per milliliter of milk.

To put that into perspective, one milliliter is a hair less than a quarter teaspoon.

Somatic cells are not a component of milk that your processor is going to be happy to see at high levels.

Ohio State mastitis researcher Larry Smith likes to say that basically, somatic cells are puss. Now you can understand why folks might get excited about the thought of 400,000, 500,000 or a million somatic cells in less than a quarter teaspoon of milk. Yuck.

So, if somatic cells enter the udder to fight an infection, high levels of somatic cells indicate that there are some infections that need attention in the herd.

Cases of infection. The National Mastitis Council is a good source of information about controlling mastitis in a dairy herd.

Old farmers have often said that if you see one rat around a farm, there are a whole lot more living there, you just don’t see them. The same can be said about mastitis.

For every clinical case that you see, there may be 15 or more subclinical cases. (OK, the National Mastitis Council did not use the rat analogy, but they did say the 15 subclinical cases part!)

If I don’t see a subclinical case, why should I care?

Even though a subclinical case does not show symptoms of a hot quarter, watery milk, clots of milk and other appetizing symptoms, the infection still impacts the cow’s level of milk production and quality of milk.

Bulk tank milk samples can tell you that there is a high or low level of mastitis in your herd. It cannot tell you what kind of mastitis is a problem or who has it.

Other critters. Bacteria are also monitored with bulk tank samples. Do they help monitor the incidence of mastitis? Generally no.

Strep. agalactiae, a contagious mastitis pathogen (a germ or critter that causes something bad to happen,) is the only mastitis-causing bacteria that will affect a bulk tank bacteria reading.

High bacteria counts can be influenced by many factors including poor sanitation of milking equipment, poor milking practices which don’t get the cows clean or dry, improperly functioning bulk tanks or precoolers.

Categories. Mastitis is categorized as environmental, which a cow picks up from her surroundings, or contagious, which is passed from cow to cow.

How can you know for sure which type you are dealing with?

The only way to really know is to culture high SCC or clinical cows. An important detail on the clinical cows is that you need to take the sample before she is treated.

It is also critical that the samples are not contaminated.

That means: clean the teat end; discard a couple squirts of milk; scrub the teat end with an alcohol pad; squirt a couple streams into a sterile tube or baggie and don’t contaminate the lid to your tube while doing the above.

Close up your sample; label sample clearly; freeze or refrigerate at 34-40 degrees F until it gets to the lab and post dip the cow if she is not getting milked out when sampling is done.

Despite efforts. Realizing that despite your best efforts, you will sometimes get a sample that doesn’t test positive for anything or is contaminated will help keep your blood pressure down.

Contaminated samples (that got a bit of dirt, manure or hair) in them may actually have shown a mastitis pathogen, but so much other crud grows on the culture plate that the lab tech can’t see anything definitive.

Plates from a contaminated sample look a lot like a forgotten bowl of fruit cocktail that has been in the back of the refrigerator for 30 days or so.

Environmental mastitis is primarily caused by coliform bacteria and strep non-ags.

There is more here than we can cover in this column and will continue this discussion in the coming months.

Today’s points. A few important points for today from the National Mastitis Council:

* The number of new infections are higher during the dry period than during lactation.

* The two weeks after dry off and the two weeks before calving are risky times for the cow’s udder (we see more new infections).

* The rate of infection is higher in the first 75 days of lactation than the remainder of the lactation.

There is often no quick fix for a high SCC. Yes, you can culture and cull the highest cows, but that is only one part of a total control program.

Long term, you need to determine what is causing an elevated counts that you can change. Based on the above three points, you can see that a cow is most susceptible to infection when she is not even milking.

Take a look. I encourage you to go out and take an objective look at how your dry, prefresh and recently fresh cows are housed.

Frequently I see very well-managed freestalls or tiestalls for lactating cows. Yet when we go out to see the dry cows, they may be overcrowded, housed on bedded packs that need to be bedded much more often or have access to muddy lots.

How a dry cow is managed has a tremendous impact on her entire next lactation. Please make sure that this cow group gets as much attention as the rest of the herd.

What you get. This may be one of those places that “what you see will be what you get” will be true - clean and dry with lower cell counts or wet and dirty with a high count.

Fortunately, processors usually reward producers financially for low somatic cell count milk.

I challenge them to fully compensate for the extra value it gives them in product yield and improved shelf life. The cows will reward you as well for any practices that lower cell count.

The relationship is well-established: cows with lower SCCs give more milk than cows with higher SCCs.

Today’s efforts to improve the herd’s somatic cell count will result in welcome additional returns in future milk checks.

(The author is the northeast Ohio district dairy specialist with OSU Extension. Send comments or questions in care of Farm and Dairy, P.O. Box 38, Salem, OH 44460.)


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