The most successful heat detection programs contain the three C's ...
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Consistency refers to uniform marking in each pen. Uniformity is especially critical on dairies where groups of breeders work together or alternate between satellite operations. Consistency means marking each cow in one direction, using the livestock marker like an ink pen and not a battering ram, and applying enough product so the color is bright. When done with a pen, the breeder should be able to look down the row and see a consistent chalk color. They've then made finding heats the next day a little easier!
Concentration. One cannot have an off day when heat detecting. Your focus needs to be on each cow and whether you need to pay closer attention to her that day. Give emphasis to allowing cows more down time out of the head locks. Heat detectors can't afford to daydream. Concentrate, make good decisions and move on!