14 January 2000

Forage analysis vital to bridge dietary need gap

MAKING up the gap between dietary requirements and forage supply is crucial to feeding ewes and having a healthy, productive flock.

That was a key point of ADAS consultant Gill Poveys talk to flockmasters at a MAFF/ADAS seminar on ewe feeding at Otley College last week.

Knowing that gap meant being aware of forage quality by having it analysed, said Dr Povey. Silage and hay are common on most sheep units and should be assessed by a reputable laboratory.

When considering individual analyses, there were some guidelines for feeding each forage, she said.

Silage should have a dry matter of 25-40%. "Anything wetter and ewes will struggle to eat it; too dry and it may show poor fermentation and reduce intakes."

Hay was less variable but worth analysing, she said. It will have far higher dry matter. "On average DM will be 84-90%. Low dry matter hay will be damp and mouldy."

The next item to search for on the analysis sheet is digestibilty or D value. For silage, Dr Povey recommended a D value of 65-70%, while for hay it should be 58-64%.

Energy and protein values vary, but silage should have an energy of 10-11.5 ME and hay 9-10.5 ME.

Protein levels for silage must be 12-18%, with variation depending on crop maturity, how much fertiliser is applied and grass type. Hay has lower protein value 8-14%.

Other items to examine on your forage analysis were ash and pH, particularly for silages, said Dr Povey. "I do not like to see ash levels in silage above 10%. More than this indicates soil contamination and risk of listeriosis in ewes in late pregnancy."

Butyric silage should also be avoided because it reduces intakes. This can be checked by measuring pH level. "It should be about four, above 4.3 suggests an unstable silage which may be butyric."

The other main forage for ewes – straw – was not worth analysing, she said. "It varies little in analysis, but there are some pointers to successful feeding. It should be clean, bright and leafy. Each ewe should be offered at least 1.5kg a head a day where it is fed."