The effects on production and behavior of mixing uniparous and multiparous cows

The production and behavior of a group of eight multiparous and eight uniparous cows after they were mixed were compared with unmixed groups of 16 multiparous and 16 uniparous cows. The cows grazed pasture (mean height 16 cm) in treatment groups in a daily paddock rotation. The milk yield of mixed cows was 3% less in the first week than cows in the unmixed groups, and 1% less in the 6 wk after mixing. The reduction in milk yield was similar for uni- and multiparous cows. Both uni- and multiparous cows in the mixed group grazed for less time and they stood for longer, particularly in the first week postmixing. The multiparous cows in the mixed group increased their pasture biting rate and became more dominant than the uniparous cows, who spent more time grooming other cows and in aggressive interactions compared with the unmixed group of uniparous cows. We concluded that the mixing of multi- and uniparous cows causes disruption to their grazing and social behavior, which results in a reduction in milk yield.