27 March 1998

Optimum date for silage cut?

DELAYING optimum harvest dates for grass silage by one week reduces silage digestibility by 3.6 units – equivalent to feeding cattle an extra 1.2-1.5kg concentrate a head a day.

However, according to Tim Keady, grassland researcher at the Agricultural Research Institute, Northern Ireland, Hillsborough, harvest date is the most influential factor on silage digestibility. "Producers must look at grass mixes to determine optimum harvest dates."

Research at Hillsborough found a three-week difference between the optimum harvest dates at 50% ear emergence for early and late heading varieties.

"Delaying harvest until late varieties reach 50% ear emergence reduces D-value by eight units relative to early varieties. Silage intake and animal performance will suffer," warns Dr Keady.

Animal performance falls directly in line with silage digest-ibility, he adds. Milk yields could suffer by 0.37kg a head a day and beef live-weight gains by 28g a head a day for each week after optimum harvest date. According to Dr Keady, thats equivalent to feeding 1.5kg a head a day to dairy cows and 1.2kg a head a day to beef cattle. &#42