Strip cup is used

The correct option is Just before milking.

A strip cup is a valuable tool used in dairy farming, consisting of a cup fitted with a dark-colored (usually black) plate or a fine mesh screen. It is employed as a critical first step in the pre-milking routine for several key reasons:
1. Early Detection of Mastitis: Squirted foremilk is visually inspected on the dark surface of the cup. The dark background makes it easy to spot abnormalities such as clots, flakes, pus, or a watery consistency, which are early clinical signs of mastitis (udder infection).
2. Hygiene and Bacterial Reduction: The first few streams of milk inside the teat canal contain the highest concentration of bacteria. By stripping this milk into the strip cup instead of the main collection bucket, farmers prevent contamination of the bulk milk supply.
3. Milk Let-down Stimulation: The manual stimulation of stripping the teats triggers the release of the hormone oxytocin, which promotes milk let-down, preparing the cow for a faster and more complete milking process.

Because the goals are detection, contamination prevention, and stimulation, the strip cup is always used just before milking begins.