Constraining the time available to graze reinforces heifers' preference for sward of high quality despite low availability

To examine these choices in terms of trade-off between diet quality and total daily energy intake, we estimated total intake and diet digestibility. The VS height constraint affected neither total intake nor diet digestibility. The time constraint caused both total intake and diet quality to decline, and intake seemed to be more markedly affected than diet digestibility. When the available grazing time was limited, heifers, by spending more than 0.60 of this time grazing VS, probably ate less than they would have done by grazing longer on RS, which provided higher intake rates. This marked preference for grazing VS of high quality indicates that heifers prioritised quality over intake when faced with the proposed trade-off.