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Detailed information and articles on grass seed and related matters |
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Maximising Protein from Forage Crops
The purchase of compound concentrate feeds represents a substantial part of the variable cost of on-farm ruminant animal production in the UK. Current restrictions on the use of animal based protein supplements coupled with increased demand for soya protein concentrates will undoubtedly put further pressure on UK farms to use alternative forage crops as a natural source of protein and energy to supplement that of grass silage.
Enhancing protein availability from forage crops is an important remit of the Institute of Grassland and Environmental Research based at Aberystwyth in Wales. Raymond Jones presents his views.
Development of new novel high protein grasses with low senescence characteristics from the IGER ‘Green Gene’ selections may, in future, provide an alternative source of conserved protein. In the meantime, a range of other forage crops high in protein content may be used to supplement grass silage, for example, legumes (red and white clover), tanniferous forages (Lotus and sainfoin with a high proportion of protected protein), brassica (kale) and seed crops such as pea, bean, lupin and rapeseed. Although considerable research information is available on the agronomic and management of these alternative crops in grazing systems, only limited information is available on their management for ensilage.
Alternative Forage Crops
Silage can be made from a large number of forage crops providing they contain adequate water soluble sugars and sufficient numbers of desirable epiphytic lactic acid bacteria; although the latter requirement can be augmented by the application of biological inoculants at harvesting. The physical structures of some alternative forage crops, for example kale, lupin and peas have restricted their on farm use as clamp silage. However, the development of chopping balers and recent advancements in film wrapping technology can provide a practical and economical method of harvesting such nutritionally valuable crops.
Almost 90 per cent of silage produced in the UK is made from grass or grass clover mixtures with maize silage accounting for about 8 per cent; the remaining crops such as fermented whole crop cereal silage, red clover and lucerne are currently relatively unimportant.
The chemical composition of a range of forage crops, with exception of the pure swards of leguminous plants of lucerne and red clover, would contain sufficient sugar substrate to ensure good fermentation, although other factors such as buffering capacity and dry matter content would also have to be considered in order to predict their preservation quality.
Challenge
Following the BSE crisis in 1996 and the continued reduction in milk and meat prices, future animal feed strategies will undoubtedly be based on forage either grazed or ensiled.
One of their major problems with grass and grass silage as a protein source for ruminants is the high proportion of rapidly degraded protein in the rumen and the lack of synchrony with available energy. Several options are available to improve availability of protein from grass sources such as stage of growth at harvesting and use of biological inoculants. Recent research at IGER has indicated benefits in using applied biological inoculants on grass silage as possessing a natural protein protection attributes.
Ensiling legumes
It is recognised that extensive protein breakdown occurs during the ensilage of forage crops, and it is not uncommon for 70% of the nitrogen content of ensiled lucerne to be in the form of non protein nitrogen. Some recent research at the University of Wisconsin, USA has shown considerable variability in the extent of proteolysis between species of legumes. The most extensive proteolysis was found in lucerne and lotus (Birdsfoot trefoil) while red clover and sainfoin showed the least protein breakdown. It has been suggested that tannins, which bind and precipitate water soluble proteins could influence nitrogen transformations and consequently reduce proteolysis. Since red clover contains no tannins it is therefore surprising to find that this crop appears to contain chemicals constituents that reduces protein breakdown.
Our current research programme at IGER sponsored by MAFF, Milk Development Council and the Meat Livestock Commission is investigating the potential of conserved high protein crops as supplements to grass silage. Provisional data from this programme suggests that inoculation of red clover and sainfoin with L. plantarum is extremely beneficial in terms of improving the rate of acidification and reducing protein breakdown in silage.
Protein components of alternative crops
There are greater possibilities for improved protein contribution to the animal from red clover, lotus and sainfoin where the total free amino acid content as a proportion of the total nitrogen is lower than that from lucerne. All the crops were established at Aberystwyth in the spring of 1997 and harvested in two cuts (except sainfoin which only allowed one harvest due to slow establishment and seasonal growth) and ensiled as bales. At present, red clover provides considerable potential for increased use on farms. After a decline for many years, sales of red clover seed have increased five-fold over the last two years. Red clover is well adapted to the soils and climate of much of Britain and is particularly suited to conventional and organic farming systems. High yields are, however, obtained only two to three years, but the high moisture content and low WSC content means that farmers need to use the good ensiling technology that is now available.
Conclusions
It is particularly important that the UK farmers identify the real opportunities of exploiting home-grown protein and energy crops in order to become more competitive with less reliance on feeding imported protein and energy to animals.
Attention must be given to the basic feed resource (grazed grass, grass and maize silage) ensuring high quality preservation, with minimum dry matter losses and improving utilisation of nitrogen supply.
- By Raymond Jones, IGER
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