14 January 2000

Mixing skills

make health

TMR mixing, vitamins and a

new approach to gilt

nutrition were topics under

discussion at last weeks

Feed Manufacturers

Conference in Notts.

Marianne Curtis reports

OPERATING a TMR mixer may seem second nature but mixing feed for the correct length of time and adding ingredients in the right order are essential to minimise digestive upsets and optimise feed use.

That is the view of Dennis Buckmaster, researcher at Pennsylvania State University, speaking at the University of Nottingham Feed Manufacturers Conference.

He explained that good rations required a mixture of large and small particles. "Small particles are more rapidly digested than large particles, more successfully ensiled and potentially increase dry matter intake.

"But large particles can also increase dry matter intake because they have a positive effect on health, and healthier animals eat more. Large particles stimulate chewing and maintain rumen pH at the correct level, helping to avoid acidosis," said Dr Buckmaster.

Research carried out at his university showed that ideally, five to 10% of the total mixed ration (TMR) should have a particle size longer than 19mm and less than 60% of the ration should be less than 8mm long.

Sieves developed by Dr Buckmaster were used to rapidly measure particle size in trials.

But particle size recommendations are also influenced by the chemical fibre portion of the diet, he explained. "Cows have a fibre requirement which is difficult to define as it depends on both particle size and chemical measurements such as neutral detergent fibre – NDF.

"For example, in a diet containing finely chopped silage, providing NDF is high, it may be possible to have a higher proportion of smaller particles in the diet and still satisfy fibre requirement. However, an index must be developed to work out feeding recommendations."

Whatever future recommendations emerge, Dr Buckmaster believes that particle size is too low in many rations due to lack of care over mixing.

"Preparing rations in TMR mixers leads to a reduction in particle size, but this can be minimised by taking a few simple steps.

"Research on Wisconsin farms showed that TMR mixing times varied between two and 60 minutes. Most manufacturers recommend mixing for five to 10 minutes. Longer than 10 minutes leads to small particles, wastes power and reduces machine life."

Adding ingredients in the correct order is also important to optimise mixing, he says.

"Fine particles such as grain, premix, concentrates and by-products should be placed in the wagon first. Next add liquids, followed by maize silage then grass silage."

This ingredient order helps protect materials such as grass silage which are particularly susceptible to break-down and reduces load on the machinery.

It is also important to wait until all ingredients are in the mixer before starting it. This helps to maintain particle size and save energy, he added.

Better mixing could have a significant effect on animal health, said Dr Buckmaster. "Farms observing these mixing guidelines have experienced much lower culling rates for displaced abomasum and a lower incidence of acidosis. In feed rejection cases, US vets and advisers are increasingly looking at ration particle size in more detail."

TMR MIXING ADVICE

No more than 10 minutes.

Add small particles first.

Dont switch on until full.

TMRMIXINGADVICE

&#8226 No more than 10 minutes.

&#8226 Add small particles first.

&#8226 Dont switch on until full.