A FOCUS on fibre content and quality should be a priority for grass breeders in the UK, according to Dr Thomas Didion, a senior scientist with grass breeders, DLF, based in Denmark.
Speaking at a symposium held at Rothamsted Research, at North Wyke, in Devon, recently, he said: “Fibre is the largest single nutritional component of forage and how digestible it is, has a major impact on the amount of energy the cow derives from it.
“If the forage is not very digestible, the rumen microbes cannot access the crucial soluble nutrients held in the cells that make up each plant. Indigestible forage will also fill the rumen up, reducing the amount the cow can eat, and will slow the passage of the feed through the entire digestive system.
“Farmers looking for high milk yields do not want either of these things to happen. Feeding highly digestible grass reduces farmers’ feed costs and produces more milk and a greater economic margin.”
High fibre grass is good for the cow as it promotes cudding and rumination and the production of saliva, which balances the pH environment in the rumen.
“It is important to give a balance between fibrous and non-fibrous carbohydrates in a ration,” he said. “Diets lacking in fibre result in low milk fat content and contribute to digestive disturbances like acidosis.”
The composition of the plant cells of grass and the cell walls that surround them changes as the season progresses. It is the type of lignin and its chemical linkages to the cell wall carbohydrates, that explain almost all the variation in how fibrous a variety is, he said.
“There is up to 15% variation between varieties in how well grass cell walls degrade and our breeders can work with that difference. Results from 17 research studies have shown that digestible fibre is positively related to increased milk yield.
“It takes 11 years to bring a new variety to the official list testing trials, using traditional breeding methods. Using new genomic selection – searching the DNA profiles of likely candidates, can shorten this by four years.
“DLF already has commercially available varieties that combine high cell wall digestibility with high sugar, lipid and protein content, such as Solomon, Cancan and Pastour. And we have been specifically looking for new varieties with this high cell wall trait for the past two years.
“We are hopeful there will soon be new ryegrasses that have particularly high cell well digestibly, as well as all the other important traits farmers are looking for in their seed mixtures, to help optimise their returns from grass,” he concluded.
n For more on grass breeding, the Ulster way, see pages 38 and 39.