Precision predictions on course for grass silage

3 September 1999

Precision predictions on course for grass silage

By Jessica Buss

GRASS silage-based livestock rations should be more accurate this winter, following the first results from the Feed into Milk, LINK-funded research project.

Feed into Milk was set up to design a new rationing system for dairy cows, replacing the current ME and MP system used, says project co-ordinator Cled Thomas from SAC Auchincruive. It is funded by MAFF, the Scottish Office, MDC and most feed supply and nutrition advice companies.

Developing the new rationing system will take another two years, but a project to standardise silage intake scores on analysis results is already completed, Prof Thomas adds.

The Feed into Milk intake prediction integrates SAC and Agricultural Research Institute of Northern Ireland silage intake prediction systems. These were already being used for near infra-red reflectance spectroscopy (NIR) analysis, but gave different results.

Bringing both data sets together eliminates conflicting results for intake prediction and simplifies interpretation of results, says SAC researcher Nick Offer. This allows more accurate and cost-effective rationing.

He says that ARINI fed beef cattle on over 100 silages, with a wide range of characteristics, to obtain its data for predicting intakes for dairy and beef rationing. SAC fed fewer samples to dairy cows for its data. Samples of variable quality were made using different cutting dates and clamping practices.

"We found that making silage on the same day in the same field using the best and worst harvesting and clamping practices causes wide variations in intakes. The worst silage resulted in 8kg of dry matter intake while the best led to 14kg DM intake, when fed with 7kg of concentrate," says Dr Offer.

Under the new system, intake predictions will be available from more labs. Analytical equipment at all leading labs has now been calibrated to ensure consistent results, he adds.

But in the short-term, because labs produce analysis results suited to different rationing systems, figures given to producers on intake potential are not directly comparable. Once the new rationing system is completed all labs will describe intake potential using the same units, says Dr Offer. However, this year most labs will give a score of 100 or above for a good silage, while one with a score of 70 is poor.

To ensure each lab produces similar analyses, there will be an ongoing process of quality control and ring tests.

Prof Thomas estimates that 40,000-60,000 silage samples will be analysed to predict intake this winter.

"This new prediction is a more robust and accurate indicator of intake potential. But it only reflects the intake potential of grass silage when it is the main diet.

"The next stage of the project is to predict total diet intake, such as when other forages or different types and amounts of concentrates are fed." That work is currently underway.

At its six-monthly meeting, in December, the project consortium will seek feedback from those using the new silage intake prediction to assess its performance on-farm.

The project is unique in that nearly all the feed industry is involved, says Prof Thomas. "This way we can be sure we tackle all the important issues, so when we come out with recommendations and changes its more likely that that the research will be used.

"In the past, feeding systems were handed down from researchers to the industry, and the industry was left to get on with it. The MP system was adapted by companies within months. There are now about 200 versions. The key aim is to ensure we develop a programme that most of the industry uses, with the same method of feed analysis."

Previously, rationing systems were developed, then researchers thought about analysing feeds to provide information for the system model: This project is developing both at the same time, he says.

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