This will ensure proper attachment, stimulation, letdown and milkout. Of course, you need to remember to turn that vacuum back to normal after test day. An investment in tagging all animals, and replacing missing tags, will improve accuracy and make record keeping and management easier too. Keep the tags clean, and don't reuse numbers from animals that departed during the current test interval. Fearing brand heat stamped and pre-numbered tags are an excellent way to maintain a good identification system.
Scheduling is everything.
Test day should be a reflection of normal production. On test day, nothing should be done differently or unnecessarily to upset the normal schedule of the cows. Starting and ending times for milking must be accurate. Milkers and Field Reps need to make sure test day stays on schedule. Exact milking times are critical, each 10 minute difference changes the factor used to calculate the non-tested milking weights.