It's that time of year when teat ends begin to show an increased amount of hyperkeratosis.
Milking machine function is probably the most important thing to consider when trying to improve teat end health. Unit on-time, pulsation characteristics, vacuum level and the liner are all significant.
Claw time has an indirect effect on teat end callusing. Overmilking contributes to teat end congestion and edema, which is related to callus formation. However, all overmilking is not created equal. Improper system vacuum or pulsation configuration may make cows much more sensitive to extended claw times.
In addition, the time spent during milk-out at flow rates less than 2.2 lb./min. seems to be critical. Remember that low flow-rate conditions do not necessarily occur just at the end of milking.
Poor let down will cause low flows at the beginning of milking, while improper automatic take-off settings can contribute to more time spent at low flows at the end of milking.
Teat end vacuum levels are also a contributing cause. A number of factors can cause the teat end vacuum to vary from the system vacuum.
The most important of these is how your system responds as milk is moved from the claw to the pipeline. The best way to determine this is by flow simulating the system and measuring the difference between claw and pipeline vacuum at varying fluid flow rates.
NMC guidelines are for the teat end vacuum to be between 10.5" Hg and 12.5" Hg. The trick is to use the flow simulation to set your system vacuum in such a way that you achieve the desired teat end vacuum range for as much of the milk-out time as possible.
Pulsation also has an effect. Even assuming that pulsators are functioning properly, the ratio and characteristics of different phases can still impact teat ends. The most commonly recognized contributor is poor massage caused by D phases that are too short.
NMC guidelines say that the D phase should be greater than 150 msec. I think a more practical target for producers is above 200 msec. There is also evidence that a prolonged D phase, as well as short A and C phases, may contribute to some types of teat end problems.
Finally, the liner is a critical influencer of teat end health. It's frustrating that little objective information exists to help one decide what the "best” liner is or what the optimal system settings are for a particular liner.
A practical way to assess liner settings is to make an estimation of what is termed the compressive load, or "overpressure.” This is defined as the force applied to the teat by the liner during the D phase when the liner is closed.
Simply put, overpressure is the difference between system or pulsator vacuum and the amount of vacuum it takes to collapse the liner. Liner wall thickness as well as hardness of the liner can affect this. Liner tension and system vacuum also have an effect.
An overpressure of 2.5" Hg to 3.5" Hg seems to be adequate for relief of congestion. Compressive loads below this range as well as above it seem to contribute to poorer teat end conditions.
You might not be able to make a totally objective assessment of the impact your milking system is having on teat ends. But monitoring the parameters above can give you better information for making systematic tweaks to your milking system. Then carefully monitor what the teat ends actually look like. The cows will tell you if you are on the right track or not.
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