We have weaned calves for four, eight, and 12 days then turned the calves and dams back together. Calves weaned at these stages all mothered-up and began suckling their dams. We measured milk production, and all cows that had their calves at four, eight and 12 days produced milk after the calves were returned. Milk composition didn't change much, depending on whether cows had their calves weaned for four or eight days. But when calves were weaned for 12 days, milk composition was slightly different, indicating that the cows that had their calves weaned at this time were beginning to dry up. It appears that a cow whose calf is weaned for at least 30 days has started the process of drying up. Even though she allowed the calf to suck, milk production was likely low. The suckling of this calf may have influenced the subsequent milk curve of the dam after her next calving. It is recommended that a dairy cow be dry for at least 60 days between lactations to prepare the mammary gland for the next lactation.
This does not seem to be an opportunistic calf and is not the norm. There are some "no-suck" devices developed for older calves that don't want to quit sucking. There was an article in Beef magazine a few years ago about research in Canada using a "calf weaner" made of a thick nylon material attached to the nose of the calf.
