17 August 2001

Low silage protein means autumn diets need rethink

By Richard Allison

FIRST cut silages have higher energy values than last year, but protein contents are again low, highlighting the need to reassess diet protein supply this autumn.

Average energy content of first cut silage is 0.6MJ/kg DM higher, at 11ME, than last years with a dry matter content of 31%, says Frank Wrights John Allen (see table).

"Intake characteristics are also good with silage generally drier and better fermented than last year. There should be no problem with low silage intakes, unlike last winter."

But average proteins across the UK are lower than last year at 12.4%, due to delays in spring fertiliser applications. And cold weather during spring delayed grass growth by 2-3 weeks, resulting in grass being cut at an earlier stage of growth than usual, he adds.

Kite Consultings Paul Macer, has also found lower silage protein contents for samples in the midlands, although not as low as last year. "This is mainly due to a reduction in the soluble protein fraction, suggesting a change in protein type."

This difference in protein type will have no adverse effect on dairy cow performance when taken into account during ration formulation. But it shows the benefits of having silage analysed before feeding.

Commenting on low protein contents, ADAS nutritionist Chris Savery says care is needed when interpreting silage analyses as they will reflect different cutting stages.

"Some producers have taken light, early cuts which have high energy and protein contents. Others delayed cutting date to increase silage yields, resulting in lower energy and protein contents."

Feeding lower quality grass silage will have little impact on cow performance when fed with other high quality forages such as maize silage and whole-crop. Producers feeding mixed forage diets can afford to cut more mature grass for silage to increase bulk, he adds.

Promar silage analyses also indicate lower silage protein contents, although grazed grass proteins have remained at 20-26%, says Promar dairy consultant Derek Gardner. "This indicates low silage protein contents are due to cutting grass when more mature with a lower leaf to stem ratio."

Lighter silage yields are also a big concern for many producers. A survey of Promar clients reveals first cut silage yields to be 15-20% lower than last year. Also, areas available for second cut were 7-8% lower because most farms were carrying extra stock due to foot-and-mouth restrictions.

"This forage shortfall is being made worse by the recent dry spell, with first cut silage already being fed to cows," adds Mr Gardner.

Second cut silage yields are particularly low in the midlands as a result of the dry spell of weather during June and July, says Mr Macer. High silage quality will also compound the problem of low silage stocks as cows tend to eat more of high quality material.

But there is potential for producing late cuts of silage this year, stresses Mr Gardner. "Following recent rain, grass growth will be high allowing silage making in September, providing there is a spell of good weather.

"Ensure that fermentation is extensive, as grass will be wet and have lower sugar levels due to shorter day length. Wilt grass when possible and do not break any silage making rules," he advises. &#42