Beware risks of using

9 November 2001

Beware risks of using

more maize in rations

By Richard Allison

EXTRA maize will be fed in dairy rations this winter to compensate for low grass silage stocks and maximise milk yields, but a carefully balanced ration is essential.

Maize silage yields are about 10-30% higher than last year, says Velcourt farms director Richard Snow. "This will allow the maize content of rations to be increased.

"Increasing maize in rations will also improve ration consistency over the winter by diluting the variability in grass silage quality, says ADAS nutritionist Chris Savery. "Consistency is crucial when maximising cow performance.

"But excess maize in rations can lead to rumen upsets and low milk fat content. This is a particular risk on units not familiar with managing high maize rations."

To avoid low fat, aim for a minimum ration fibre content of 32% and a maximum combined starch and sugar level of 28%. Also ensure adequate ration mixing to prevent cows selecting concentrates and refusing forage in mixed rations, says Mr Savery.

Last winter, Norfolk producer Richard Thompson experienced low milk fat when feeding high levels of maize silage. A high maize ration together with feeding high levels of parlour concentrate was identified as the cause.

"This winter, increasing maize silage chop length by 10mm, moving to a total mixed ration and including 1-2kg/day of hay are helping to maintain milk fat %. Bedding cows on straw also helps to prevent low milk fat because it offers a good source of fibre," says Mr Thompson.

Low milk fat will be a particular problem this year as producers push for milk output by feeding more concentrate, says Mr Snow. "When high concentrate rations are fed on our units, sodium bicarbonate is included to help buffer the rumen."

Another potential problem for high maize diets this winter was revealed by the free ration check service offered by farmers weekly, fwi and Velcourt (Livestock, Oct 5). "Many rations contained insufficient protein as a result of this years low grass silage protein levels. Feeding more maize will make this situation worse," warns Mr Snow.

Ration protein levels should be increased to 17.5-18.5% by including soyabean meal, rapemeal or maize distillers. Urea can be included at 100-200g/day as a cheaper alternative when rations contain more than 80% maize, but it needs careful handling and thorough mixing.

Also check the mineral content of rations as maize contains less minerals than grass silage, says Mr Snow. The Ration Check service found that many rations for cows yielding more than 30kg/day were calcium deficient. This can be easily corrected by including limestone flour in the ration.

Another bonus for producers this winter is that maize silage quality is higher than last year, says Frank Wrights ruminant manager David Wilde. "Early results from our labs show maize contains nearly 0.5MJ/kg DM more metabolisable energy than last year."

The higher energy content of maize is due to an additional 2% starch and higher silage digestibility. Based on the Feed Into Milk rationing programme, this means cows will produce 0.4kg more milk without increasing concentrate use.

This improvement in milk output will boost gross margins by up to £25/cow, explains Mr Wilde.

However, maize silage analysis by Promar Laboratories during October show little difference from samples analysed at the same time last year, says lab director Rob Holliday. "Metabolisable energy content has remained at 11.5MJ/kg DM, while D-value is slightly lower this year at 72%."

There are still many samples expected for analysis this month and trends may change over time, adds Mr Holliday. &#42


&#8226 High maize rations.

&#8226 Check ration protein.

&#8226 Higher maize silage quality?

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