Cows in clover give more milk

摘要

Improvements in yield of 15 percent have been achieved in the latest trials at IGER, North Wyke, where cows have been alternately grazing pure swards of grass and white clover. Given the choice it seems cows prefer to eat clover rather than grass -but the preference changes depend on time of day. Previous research on grazing preferences at North Wyke with free access to adjacent swards of grass and pure clover showed that cows have a preference for a 70:30 mix of clover:grass in their diet. The work also showed that cows prefer to eat clover in the early part of the day with the bulk of the grass being eaten in the evening. Although it is not entirely clear why, research scientist Mark Rutter puts forward two possible theories. "Even though cowshave no predators they are evolutionary 'hot wired' to avoid grazing at night so opt for grass in the evening because it has a slower rate of passage through the gut," he says. "An alternative reason is that water soluble carbohydrate levels build in thegrass during the day so that it tastes sweetest in the evening." Putting these findings to the test in the most recent study, 24 early-lactation cows were divided into six groups of four. Three groups were given free access to a fresh area of a mixed grass/ciover sward after each milking. The other three groups had access to a fresh block of a pure clover sward after the morning milking and were then turned out to a fresh area of grass following the afternoon milking.