Partner und Internationale Organisationen
(Englisch)
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AT, BE, BG, DK, FI, FR, DE, EL, IS, IE, IT, LT, NL, NO, PL, PT, CS, SI, ES, SE, CH, UK
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Abstract
(Englisch)
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Authors: H. A. van Dorland, H.-R. Wettstein, M. Kreuzer: Forage legumes provide environmentally friendly alternatives for artificial N fertilizer required for plant growth, and can be considered as protein sources for ruminants. However, a drawback of feeding non-tanniferious legumes such as white and red clover is the relatively poor utilisation of protein by the ruminant. On the other hand, there are indications available that feeding legumes enhances the proportions of n-3 fatty acids in the milk fat, fatty acids which are considered beneficial to human health. At present, few studies are available that compared white with red clover as addition to ryegrass for dairy cows, for these aspects. In the project, the effects of white and red clover addition to ryegrass on nitrogen use efficiency, performance, milk quality, and eating behaviour in lactating dairy cows were studied. Additionally the agronomic performance of the forage legumes were tested in a Europe-wide common protocol, a dairy sheep experiment was carried out at high altitude and, finally, the current usage of forage legumes by Swiss organic farmers and the corresponding status of the milk fatty acid composition was determined by a questionnaire and laboratory analyses. The four dairy cow experiments, the central activity involving a total of 96 dairy cows of Holstein Friesian and Brown Swiss breed types, and one manure storage trial were carried out in the period from 2003 to 2005. The cultivars under study in these trials were white clover ('Klondike'), red clover ('Pirat'), and ryegrass ('Fennema'), and the clover/ryegrass mixtures that were used in the experiments always consisted of 40 % clovers, on dry matter basis. The silages in this project were wilted before ensiling and ensiling was preformed without the use of additives. The white and red clovers investigated were found to be widely equivalent in utilisable energy and protein supply, also in comparison to the ryegrass. Due to an unusually high crude protein content of the ryegrass in the first two experiments, it remains open whether these forage legumes, when supplemented to a moderate-protein ryegrass, would have contributed to metabolic protein supply or would have merely increased metabolic nitrogen load. The white and red clovers investigated were also similar in their effects on N losses and methane emission in dairy cows. It was concluded that supplementation of white or red clover to a high-protein ryegrass would enhance nitrogen losses to the environment to a certain extent, and would not be effective in abating methane emissions. Forage form and type, along with forage quality, were observed to play a role in eating behaviour of dairy cows, and preferences for clovers over ryegrass were only developed when a large difference in nutrient concentration and energy between the forage types existed. Although, preference for forages therefore may not necessarily affect the resulting milk yield and composition, proportions of poly-unsaturated fatty acids and n-3 fatty acids were shown to be affected by a preference for clovers over ryegrass. In this respect, the investigated forage-based diets in fresh form proved to be superior for increasing the proportions of both poly-unsaturated fatty acids, n-3 fatty acids and conjugated linoleic fatty acids, compared to the silage-based diets. With regard to clover type, white clover seemed to be slightly superior to red clover supplementation for enhancing the proportions of n-3 fatty acids. However, the effects of clover supplementation were generally larger than those of clover type, although beneficial (more n-3 fatty acids) and undesired effects (less conjugated linoleic fatty acids) were partially compensatory with clover addition compared to clover omission in a ryegrass-based diet. Trifolium pratense nivale, although cultivated from seed collected at high altitude, did not significantly establish when sown into an existing pasture at 2000 meters and, consequently, the proportion of legumes could not be increased as intended. Grazing of dairy sheep on a high altitude pasture naturally richer in legumes than another pasture did not significantly alter the fatty acid profile of the milk fat. The herd milk survey demonstrated the large variability in the usage of forage legumes across organic farms, with altitude and soil type playing a certain role. Milk fat composition did not clearly depend on the proportion of legume rich pastures and meadows of the farm, but proportion of n-3 fatty acids was clearly higher than published values from farms using maize-silage based diets. At temperate climate, like in Switzerland, the plot experiment as part of the common protocol showed the superiority of red clover and white clover over birdsfoot trefoil and lucerne in binary mixtures with ryegrass in a simulated grazing system with intervals of 30 days between two harvests. Birdsfoot trefoil and lucerne showed a weak persistence and disappeared relatively quickly from the plots. For lucerne this occurred despite the fact that a special variety was used that should be suitable for grazing. In future, further options need to be explored for minimising the negative impact, and take advantage of the positive aspects, of feeding clovers as additions to ryegrass-based diets for milk producing ruminants, in order to increase and improve the utilisation of clovers in farming systems, as clovers remain undoubtedly a vital component of environmentally-friendly sustainable farming systems.
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