September 5, 2017 at 3:32 p.m.
Is your bathtub running over?
Think of your herd's somatic cell count as water in a tub. It could be very full, representing a high SCC, nearly empty, for a very low SCC, or in the middle. Water coming in the tap is newly infected cows. Water going out the drain is cured and culled cows. Reducing your herd's SCC is just like lowering the water level in the tub. This too, is a simple concept yet it is often misunderstood or poorly implemented. How does one accomplish this?
First, turn off the water. Ever heard of the hole theory? The hole theory says that if you are in a hole, the first thing you must do is stop digging. Turning off the water means preventing new infections. Preventing new infections happens when you figure out the reservoir of infection and the means of spread. Typically the reservoirs are infected cows, the cow environment and teat skin. Transmission occurs during and shortly after milking, and to a lesser degree throughout the day.
Turning off the water is the most important way to reduce your herd's SCC. If you do not accomplish this, the only way to reduce the SCC is to have the drain wide open, which usually means culling an awful lot of cows. This is a very expensive way to control the level in your tub. It is like opening the drain but leaving the hot tap water running 24 hours a day.
Turning off the tap means five to seven percent new infections per month or less, as calculated by a change in somatic cell count for the cow - not the quarter - from less than 200,000 to more than 200,000. This number is reported on your DHI report. Turning off the tap can also mean less than two percent of your lactating herd coming down with clinical mastitis per month, or less than two percent of your lactating herd having milk discarded from treatment on any given day. Every herd can have a somatic cell count below 200,000, according to noted mastitis control expert, Dr. Andy Johnson. The first and most important step to accomplish this is to turn off the tap.
Fortunately for those of us who like low herd somatic cell counts, every cow eventually gets culled. I do not mean to be callus, but having a perpetually leaky drain does help empty the tub. So if you do a really good job of turning off the tap, eventually the water level will drop. Yet, in most herds it is important to open the drain too. Infected cows (water in the tub) can serve as sources of infections for other cows. They will turn the tap back on the minute you go under to wash your hair. This is particularly true if you have cows infected with what are commonly called contagious pathogens. These are primarily Staphylococcus aureus, Streptococcus agalactia and Mycoplasma bovis. Cows infected with these organisms must be culled or treated to turn off the tap.
To a lesser extent cows infected with environmental or skin organisms can serve as reservoirs, too, but we typically consider them less important sources of infection. The best way to open the drain is to find infected cows, diagnose the cause of the infection and treat them appropriately. Some infections will be essentially untreatable and a decision must be made to either cull, stop milking the infected quarter or keep the cow and infected quarter in the herd. The most important point here is that we need to find the cow and make a decision. If you have done a good job turning off the tap, opening the drain is pretty easy.
It is also very important to find newly infected cows quickly before they become a big stream of water entering the tub. Use your powers of observation and your records to find them. Use the California Mastitis Test and milk cultures to diagnose the offending organisms. Use the appropriate treatments to cure them. It is much easier to do this before they get into the tub than later. Find them and make a decision. If you ignore them the water level will rise.
Attacking the problem of a tub too full requires a systematic approach. Your veterinarian is the person best equipped to outline this approach, help you implement it and monitor its success. This is what we do. The days of using your veterinarian to only recommend, sell or administer the "best" treatment for all mastitis on your farm are long gone. They left with five cent pop and nineteen cent gasoline. There are no miracles inside that black medical bag or Chevy pickup. The steps of a systematic approach are not difficult, and your veterinarian can help, but only if you make a commitment to lower the water level in your tub. He or she cannot do it without you.
Dr. Johnson is also fond of saying that the SCC of each farm is exactly what they have decided it should be and that it reflects the true attitude of the dairy. This may sound harsh, but usually the only major difference between farms regarding somatic cell counts is attitude. All tubs can be below 200,000.
Jim Bennett is a dairy veterinarian at Northern Valley Dairy Production Medicine Center in Plainview, Minn. He and his wife, Pam, have four children. He can be reached at bennett[email protected] with comments or questions.[[In-content Ad]]