A study by researchers at the Agri Food and Biosciences Institute (AFBI) into the effect of grazing silage fields with sheep during the winter has found mixed results.

Experiments were conducted in Hillsborough, Co Down over two winters, with silage swards grazed by sheep for three to four weeks from mid-November, while other ground was left un-grazed.

First cut silage was harvested as usual the following May.

Results from the study, which have been published in journal Grass and Forage Science, show silage quality was unaffected by grazing during the initial experiment over the first winter.

However, the second experiment conducted during a different winter found the metabolisable energy (ME) of silage from grazed grass was 0.5MJ higher than the un-grazed sward.

The impact on the performance of late lactation dairy cows that were fed the silage from the two experiments was also mixed.

In the first year, dry matter intakes were unaffected, although milk yields were 0.8kg/day higher and milk protein yields were also improved in the cows offered silage taken off winter grazed swards.

In the second year, dry matter intakes were 1.5kg/day higher with cows fed the winter grazed silage and there was an increase in fat yield.

However, across both experiments, fat plus protein yield was unaffected by silage type.

“Winter grazing using sheep has potential to improve silage quality, but with marginal benefits on individual cow performance,” the AFBI researchers conclude.