Sweet Success with High Sugar Grasses; IMPRESSIVE Results Have Been Achieved with High Sugar Grasses (HSGs) Bred at the Institute of Grassland and Environmental Research (IGER) at Aberystwyth. Farming Life Editor, DAVID McCOY, Joined Personnel from Three Northern Ireland Companies, James Coburn & Son Ltd, Samuel McCausland Ltd and Joseph Morton Ltd, on a Visit to IGER
CATTLE and sheep are actually poor converters of grass protein into milk and meat.
When grazing ordinary grass, livestock use only about 20 per cent of protein from the herbage for production - most of the rest is wasted in faeces and urine.
This is not only financially costly, but also detrimental to the environment.
A major reason for these lossed is the imbalance between readily available energy and protein within the grass. Proteins are rapidly broken down when feed enters the rumen. However, when the diet lacks readily available energy, the rumen microbes can use less of the nitrogen released from the feed, so much of it is absorbed as ammonia and eventually excreted.
Grass cell walls consist of the complex carbohydrates, cellulose, hemicellulose and lignin. Although these components can be broken down, this takes time and the carbohydrates are not, therefore, available early on, when grass protein is broken down in the rumen.
Water soluble carbohydrates in grass are the sugars found inside the plant cells, rather than in the cell walls themselves. They become a source of readily available energy soon after forage enters the rumen, allowing rumen microbes to process more grass protein. This protein can then be used in the production of meat and milk.
Through this mechanism, HSG varieties, with high levels of water soluble carbohydrates, can significantly improve the utilisation of protein in grass.
Research at the Institute of Grassland and Environment Research (IGER) at Aberystwyth in Wales has shown that HSG varieties have consistently higher levels of sugars than standard varieties throughout the grazing season. Water soluble carbohydrate levels up to 50 per cent higher have been recorded in some HSGs. However, studies have shown even a small difference in the level of water soluble carbohydrates can have a big effect on ruminant performance.
Results of several studies conducted on commercial dairy farms and by IGER at its dairy unit near Aberystwyth, show that grass protein is used more efficiently for milk production when extra energy is provided by feeding HSG varieties.
Animals were fed either an experimental HSG or a recommended control ryegrass variety. Both grazing and zero-grazing were used in the assessments.
The main advantages of feeding HSG varieties were found to be:
l Milk yield increased substantially
In an early study that looked at Italian ryegrass across six commercial dairy farms, animals averaged six per cent more milk per cow over the grazing season.
In recent zero-grazing trials with perennial ryegrass, the average milk yield of animals fed HSG increased by 2.3kg/day in early lactation and by 2.7kg/day in late lactation, without a detrimental effect in milk quality.
l Dry matter intakes improved significantly
Zero-grazing trials at IGER found that dry matter intakes rose by around 2kg/head per day. This is particularly important in low input farming systems where producers want animals to obtain as much of their nutrients as possible from grazed grass.
l Diet digestibility increased
In the same trial, a three per cent improvement in diet digestibility was recorded with HSG. …