I have had several conversations with dealers and their employees concerning appropriate vacuum levels for various systems. Vacuum level is dependent on the consistency of udder preparation, liner type and takeoff settings. A standard answer I give to all these inquiries is to shorten milk hoses as much as possible.
Shorter hoses will raise the vacuum at the claw during peak milk flow, but not raise the vacuum level that teats are exposed to either at the front end of milking with poor udder preparation or at the end of milking with dry takeoff settings. An additional benefit when shortening hoses is improvement in unit alignment in almost every dairy due to less pull from excessively long milk hoses. Cows will milk faster, there will be fewer liner slips or squawks and the overall milking ability will be improved. All herds will benefit from shorter milk hoses.
Shortening the hose length will also reduce the lifting of milk in milking parlors. The vacuum drop in any given parlor is a factor of the hose length and the amount of lift. In this dairy I made three recordings in succession, the first and third with the hose as found, the middle with the hose leveled (see table below).
A 0.3'' increase in peak milk flow is significant. Simply lifting the hose increased the claw vacuum during peak milk flow in this installation, but cutting the hose shorter will increase the claw vacuum to an even higher level. A common concern is how to handle cows that either misload in a parlor or stand at an angle in a tiestall barn. The solution is to have several short sections of milk hose with a stainless nipple attached to one end. This short hose can be added to the newly shortened normal hose to milk any of these problem cows. These hoses must be washed after every milking by installing them at any stall in the parlor or barn to allow normal cleaning.
After the results of this testing were discussed with the owner and parlor manager, the milk and pulsation hoses were shortened, which improved the overall parlor performance. The discussion of the results centered on this message:In this herd,about 97% of the cows were milked with excessive hose length so 3% of the cows could be milked properly. The dairy now milks 97% with correct hoses and uses hose extensions on the 3% that need it.
The hose length in tiestall barns can be standardized by installing new stallcocks to insure all stallcocks are located in the same location by every two stalls.
Often times when stall barns are remodeled the stallcocks are not changed. There is no limit for the number of inlets on a high line pipeline. Excessive loops in stall barns is a very common issue that impacts milking performance.
For more on milk quality, read: