31 December 2009

4 minute read

Europe

"Dairy farmers have often wondered why cows milk better after Christmas and these findings explain why."

According to FarmersWeekly, Mr Torrens discovered, irrespective of variety, using bioparametrics and rumen liquor, fresh maize had a much lower ME than expected.

"Fresh maize was shown to have a metabolisable energy, ME of about 10.4MJ/kg DM. Results also showed it took about six-and-a-half hours for the rumen to process the material and extract ME."

However, after two months in the clamp, ME had increased to 11.0MJ/kg DM and after five months ME was up to 11.4MJ/kg DM.

"By the time maize had been ensiled for five months, there was good ME release and faster throughput through the rumen." And after nine months of fermentation, the 'lag time' in the rumen had also improved, taking three-and-a-half hours for material to be processed.

"The long and short of it is, if you feed fresh maize, you aren't going to get as much milk," he said.

But if you are forced to feed fresh maize, it is essential rations are balanced accordingly.

"The trouble is, maize analysis is set up to assess fermented maize rather than fresh maize, so test results may not give an accurate picture of ME," said Mr Torrens.

"It is essential, farmers and nutritionist realise fresh maize will have a lower ME than expected and manage ration formulation accordingly."

When this is not taken into account, cows could be sold short on energy, said David Bright. "It may be necessary to feed processed wheat or crimped maize with fresh maize to make up the short fall in energy until the crop has had time to ferment."

Starch degradability

The longer the crop is in the clamp, the more time there is for the acid from fermentation to act on the grain and improve starch degradability and digestibility, explained consultant Robert Bull.

"This is why we see improved ME once the crop has had time to ferment in the clamp."

The trouble with the type of maize we grow in the UK is the starch is not available to cows straight away. "Maize suited to our environment has high levels of hard, encapsulated starch which are not useable by the rumen."

The key is to make this starch available to the cow. "A good example of starch availability is comparing dry grain maize with crimped maize," he said.

"About 20 per cent more starch is available to the cow when using crimped maize compared to dry grain."

Although dry grain may be ground or cracked, the protein is 'locked up' and not available to the cow. The acid used to crimp maize and the acid produced in fermentation makes the starch more available.

"Feeding dry maize is a lose lose situation for ruminants - crimped maize is a far more effective way of feeding starch."

In forage maize, a similar principle applies as crimping. "Acid produced by fermentation acts on the grain to improve digestibility, however, the process is not as effective as crimping so it takes months for the acid to act."

And the cost of reduced starch digestibility of recently ensiled maize silage could be as much as 2.5 litres a cow a day. "And to compensate for this you will need to feed 1kg of wheat a cow a day more," Mr Bull said.

"To ensure you get the best from maize, ensure you have roll-over stocks and when roll-over maize is not available you must make allowances for potential reduced energy supply in the diet."

Having achieved degradability in the clamp, you should then consider whole plant digestibility in the rumen, said Mr Torrens.

Whole plant digestibility

Traditionally maize varieties have been selected for starch. However people are beginning to realise digestible fibre is just as important and has a huge effect on controlling intakes.

"We need to start talking about 'total' plant digestibility by thinking about a combination of starch, fibre and how digestible the total plant is." If maize is bred for high starch there is a tendency for fibre to become more difficult to digest, resulting in reduced intakes.

"When a farmer wants more milk from forage, it is essential to have high plant digestibility so material can be processed quicker. This will increase forage intakes and thus milk production."

And as farmers include more maize in the diet, it is essential to use a crop with high digestibility and lower starch, if this is not balanced there is the potential to overload on starch as the cow eats more.

"In response to this, Maisadour is beginning to select varieties based on this criteria, it is important that the UK selection process follows in a similar way."

But digestibility is also in the farmers hands. "High dry matter in mature fermented maize will increase NDF and reduce digestibility so it is important the crop is harvested on the correct date at 30-35 per cent DM."

TheCattleSite News Desk