In the last year, I have reviewed in extensive detail the somatic cell count (SCC) records from dozens of DHI-monitored and robot barns. As a result, I re-educated myself as to the dynamics of reducing high SCC in any particular herd in order to achieve a lower incidence of mastitis and higher milk production.
My first review started with an average 125-cow dairy barn, whose monthly herd SCC seem to hover just below the milk board penalty of 400,000/ml with some top milk producers topping three to plus-nine million SCC.
In six months of evaluation, I would like to take the credit that I put together a fantastic SCC-fighting nutrition and management program, but that is not what happened. This producer was forced to cull out about a dozen persistent culprits that scored SCC over one million and now maintains a herd SCC of about 225,000/ml. In addition, the herd’s milk production increased by 2.5 kg.
This individual’s case is not unique, because it is no secret that high SCC bulk tank records rob this dairy and others of otherwise good health, milk production and revenue. Consider the following relationship between SCC and milk production outlined in the following table (Philpot and Nickerson, 1991)
In addition to these milk production losses, there is also a loss of quality tin the milk produced by high SCC cows. White blood cells from high-SCC milk contain natural enzymes that break down valuable milk protein and fat. As a result, milk processors do not want high-SCC milk because casein protein levels are significantly lower, which negatively impacts such milk end-products such as cheese yield. There is also some evidence that SCC deterioration of milk leads to reduced fluid milk storage life.
Nobody should dispute that lowering SCC will eventually lead to higher milk production in the dairy herd. However, I have learned that all available SCC records, whether they come from DHI, robot or any other SCC record keeping system, should be routinely reviewed, and an effective plan of action can be taken.
Important points on SCC
Here are some of my own revelations to effectively combat high SCC in lactating dairy cows that I learned by examining many recent SCC reports:
- It’s a “numbers game.” A high-milk-producing cow with a modest SCC count can produce the same total number of cells as a modest milk-producing cow with a high SCC count. For example: A 40-kg cow x 200,000/ml SCC = A 20-kg cow x 400,000/ml. Their contribution to the bulk tank should be the same. Similarly, a 10-kg cow x 200,000/ml is a lower contributor.
- There is a “Million SCC Club.” I always take note of the lactating dairy cows that score one million SCC/ml and more. Their SCC multiplied by milk production often yields a substantial SCC contribution to the bulk tank. On the DHI records, these cows are reported on the HSLST. On the robot records, I find similar cows by transferring and sort them on my excel spreadsheet.
- “A few bad apples…” never was a cliché so true to me. For example, if one looks at the same HSLST sheet, there biggest SCC violators make the biggest contributions. I know of cases where the dairy producer is milking several hundred cows, and less than a dozen cows contribute up to 40 per cent of his bulk tank SCC. I know of a couple of cases where the highest-SCC cows were culled and the whole herd SCC easily dropped 100,000 points.
- Impact of corrective action. It’s a no-brainer that either culling or therapeutic treatment of dairy cows in the Million SCC club has a significant impact on the rest of the herd. I also found that implementation of a solution that reduces SCC in the second-highest group of SCC cows with records of 200,000-800,000/ml will also lead to lower whole herd counts. That’s because, these cows have relatively high milk production, which gives them modest control of the bulk tank.
- Law of diminishing results. The first 50,000 cell/ml of an individual cow SCC record denotes shed body cells, while the rest of the record is white-blood cells fighting infection. Therefore, lowering the SCC of a herd by the same rate with a SCC of 200,000/ml versus another herd with a SCC of 300,000/ml can be more difficult to achieve in the former.
I believe that many dairy producers can start reducing high SCC in their dairy herds by a periodic review of all their available SCC records and apply some of these revelations in an effective corrective manner.