13 February 1998

A GREATER ROLE FOR FORAGES

More of UK ruminants

protein requirements could

be met from forages in the

future, reducing

requirements for more

costly purchased protein

feeds. FW livestock

reporters unveil the latest

research under way

to improve the quality of

grass and forages

MICRIOBIAL and undegraded dietary protein supply from grass could be improved with new breeding programmes and careful use of alternative forages.

Prof Roger Wilkins of the Institute of Grassland and Environmental Research, North Wyke, suggests that crude protein measurements do not accurately describe the amount of protein available for utilisation.

"Although grass has high crude protein levels, it is rapidly broken down so that undegradable dietary protein and microbial protein produced is relatively low," says Prof Wilkins.

"This means that rumen bugs cannot work quickly enough to get the most out of the grass. To increase rumen bug activity grass plant varieties could be bred with 20% higher sugar levels because these characteristics are now known to be heritable and to vary between varieties," he says.

Methods could also be adopted to slow down the passage of grass through the gut so that bugs have more time to break down protein.

Prof Wilkins suggests that one option is to breed more stay-green grass varieties. These maintain their protein content for longer and could prove more resistant to protein breakdown in the rumen.

Forages such as sainfoin and birdsfoot trefoil with high tannin contents could also help to slow protein breakdown because tannins bind with proteins, blocking enzyme activity.

Quoting trial work carried out in New Zealand, Prof Wilkins suggests that birdsfoot trefoil allowed an increased protein absorption in the small intestine of 50%.

"However, it is possible to have too high a tannin content so that breakdown is too low and about 2-4% tannin level appears to be optimal," says Prof Wilkins.

"Tannin is also present in grasses and it may be possible to breed varieties with higher tannin levels in the future," he adds.

IGERs Raymond Jones also believes that forages that provide protein could be used to replace some of the soya brought into the UK each year.

Reducing soya imports by half would mean finding 190m tonnes of crude protein from other sources. That would mean increasing acreages of protein crops – including red clover, lucerne, kale and peas – from 134,000ha to 468,000ha (54,000 to 189,000 acres).

But Mr Jones believes that improved conservation methods, and accurate measurement of true protein in the different crops could decrease the acreages of protein crops needed.

"Extra protein may come from altering the protein composition of grasses, such as the development of stay-green grass varieties, but that will take time to develop."

Red clover has the potential to supply more true protein in silage than many other crops, he says. However, lucerne, sainfoin and lotus are also low cost protein crops that have potential – kale and beans are more expensive to produce. Sainfoin and lotus also have increased potential because of their natural protein protection.

Improving conservation management may also affect true protein content of silages, he says. Encouraging good lactic acid bacteria naturally by chopping silage crops when harvesting that seems to activate bacteria or with inoculant additives could increase true protein.

Inoculant additives have improved beef liveweight gains by up to 38% in IGER studies, he adds.

At Aberystwyth, a wet site, he has been encouraged by the yield achieved with a crop of lucerne that yielded almost 6t of DM/ha (2.4t/acre) in its first year. Lotus has also performed well yielding 4.6t/ha (1.9t/ha). &#42

INCREASING PROTEINS

&#8226 Use of stay-green grass varieties.

&#8226 Tannins to slow protein breakdown.

&#8226 Red clover, lucerne and lotus.

&#8226 Inoculants to increase true protein.


British scientists are keen to find out how more of a cows protein requirements could be met from home-grown forages to cut feed costs.

British scientists are keen to find out how more of a cows protein requirements could be met from home-grown forages to cut feed costs.