Grassland and forage crops

With many dairy farms grazing sheep to tidy up silage swards over the winter, this two-year study by AFBI in Northern Ireland was set up to examine the impact of tack grazing on silage quality and subsequent cow performance.

Allowing sheep to graze the swards during December resulted in a reduction in 1st cut yields of 0.8 and 1.0 t of DM/ha in year 1 and year 2, respectively. Year 1 was a milder winter, while year 2 had a number of frosts which likely delayed sward recovery. The nutritional value of both treatments were similar, except for metabolizable energy. The ME of the ‘grazed’ treatment silage was 0.2 MJ/kg DM higher than the ‘un-grazed’ treatment in year 1, while in year 2 the difference was 0.5 MJ/kg DM.

In year 1 silage DM intakes were unaffected by winter grazing management, however cows offered silage from ‘grazed’ swards produced 0.8 kg more milk per day or an increase of 0.3%. In year 2, DM intake increased by 1.5 kg per cow in the group offered silage from ‘grazed’ swards, which did not result in an increase in milk yield but did increase milk fat content by 10%.

The benefits or otherwise of removing autumn growth by grazing sheep will likely be influenced by weather conditions over the winter and spring, and the impact this will have on sward growth and/or die-off. Whether you graze or not, heavy autumn covers should be grazed off by mid-December, but not too tightly as this could dramatically slow spring growth.