23 November 2001

Clover & grass boosts milk yields

GRAZING dairy cows on clover by day and grass by night could boost milk yields by nearly 3kg/day, according to research from the Institute of Grassland and Environmental Research at North Wyke, Devon.

Addressing the BGS Winter Meeting, IGER researcher Mark Rutter acknowledged that previous research at the institute, using alternate strips of grass and clover to offer cows greater choice, could sometimes be difficult to implement in practice.

"Growing grass and clover in separate fields offers more scope to apply fertiliser and herbicide regimes best suited to the two species."

Previous studies at IGER showed when offered a choice, grazing cows eat 70% clover and 30% ryegrass. "There is also a daily pattern with a stronger preference for clover in the morning and preference for grass increasing towards evening."

Using this information about daily preferences, Dr Rutter designed a six-week trial in which cows were turned on to clover pastures after morning milking and grass pastures after evening milking.

"Results show that, compared with cows grazing a mixed grass/clover sward, cows grazing separate grass and clover swards had higher dry matter intakes and produced 2.93kg/day more milk. This is because they spent less time searching out preferred herbage and more time eating."

Addressing producers concerns about bloat on 100% clover pastures, Dr Rutter said it was unlikely to be a problem. "In trials, we give cows an anti-bloat preparation, but this is probably unnecessary. Grazing them on clover by day also means it is easier to keep an eye on them than if they were grazing it by night. It is also best to introduce cows to pure clover swards gradually."

One organic producer was concerned growing grass and clover separately would lead to loss of the benefit of recycling of nitrogen from clover to grass in mixed swards. "We need more studies to assess how much nitrogen is recycled by cows via dung and urine when they move from clover to grass pastures, which may compensate," said Dr Rutter.