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By Manfred Coenen
Institute of Animal Nutrition, University of Veterinary Medicine, Hanover
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Pasture is not always available to horses. Haylage can serve as a good and very flexible substitute. Drying as a process to conserve grass or other feeds is probably as old as the horse as a domesticated animal. Despite extensive knowledge about producing high quality hay and the availability of technology to improve the drying, the process still depends on the weather condition.
Farmers in many European countries are therefore unable to constantly supply their horses with hay of sufficient quality. Haylage, on the other hand, offers farmers the same opportunities as hay in terms of nutrition and energy as well as other distinct advantages, although some potential issues linked to feeding haylage to horses are object of discussions and further research is needed to elucidate best practices.
Suitability of types of silage for horses
For horses, the dry matter (DM) content of grass silage is an object of discussion. The feeding practice prefers silage with a DM content of more than 60%, a product also called haylage. The reason for the high DM content is a less strong acidic smell. A lower DM content has the following benefits:
1. Limited wilting time, implying a limited period for growth of moulds prior to baling and a more intensive acidifying process (with a stronger aerobic stability as a consequence) after opening of the bales.
2. A DM content between 400 and 500 g/kg seems to be appropriate for horse silage.
As a source of nutrients and energy, haylage in general is not different from hay. The figures 1 and 2 show the distribution of protein in silages and hay. These are results from a survey in Germany in 34 farms with 467 horse; 239 of them received grass silage as the only roughage (Müller 2002).
Figure 1: Distribution of protein concentration in roughage for horses: haylage
Figure 2: Distribution of protein concentration in roughage for horses: hay
Although there is a shift towards higher protein concentrations in silages in comparison to hay, it is obvious that under practical conditions both feeds will contribute similar amounts of crude protein to the daily intake if comparable amounts of DM hay or silage are fed. In fact, further results from that study (Müller 2003) showed that the DM intake by haylage rations is not very different from DM consumption by hay including rations (Fig. 3).
Figure 3: Daily DM intake in horses by ration containing either hay or haylage as the only roughage
So far we can conclude that haylage and hay offer the same opportunities in terms of nutrition and energy intake. Some restriction should be considered for protein: during the ensiling process a proteolysis occurs, which is an unpredictable factor. The consequence is that, although the protein concentration is identical, the amino acid intake is different between haylage and hay. This should be elucidated in more detail by further research. In practice, the protein supply for lactating mares and partly for foals often does not correspond with current recommendations and a decrease of protein quality must be compensated.
Safety of haylage for horses
A frequently recognised deficit of hay is the high contamination by bacteria and/or moulds. The dusty and mouldy hay quality creates a remarkable burden for the respiratory system. Haylage offers a clear benefit in this area.
Sometimes, microbial control shows that the amount of bacteria, moulds and yeasts in haylage can be high also (Wolf et al. 2005), as a result of a disturbed intestinal microbial community, leading to colic or diarrhoea. Although it is much more difficult to define a safety limit for micro-organisms in feed compared to contaminants like heavy metals, a safe quality standard can be described (Kamphues 2005).
To achieve this quality status, it is helpful to use proper preservatives. Compared to silage for ruminants, where the improvement of feed value and intake are decisive aspects for choosing additives, haylage needs to possess a superior aerobic stability. An increase in bacteria, moulds and especially yeasts after opening the bales make the haylage clearly less suitable.
Haylage is often associated with the risk of botulism. It is assumed that (parts of) cadavers in the ensiled material are the main reason for the occurrence of Clostridium botulinum. It can be the origin of those bacteria that produce the toxin under anaerobic conditions. But the contamination of cut grass by soil is a remarkable risk factor too, possibly more relevant than cadavers are. The simple fact that these bacteria are regularly detectable in soil of many parts of Europe needs to be considered in the production of haylage. Several studies show that the use of manure and embedding from poultry production as fertilizers can dramatically elevate the occurrence of Clostridium botulinum in the soil for many years. For that reason poultry litter should not be used on grassland.
Occasionally horses show watery or moist faeces and horse owners suggest that this may be a problem associated with feeding haylage. However, neither experimental work nor surveys conducted in feeding practices have provided to date any valid indication that haylage feeding influences the formation of faeces. The reasons for the changes in faecal consistency remain unknown. However, our experience shows that the addition of sugar beet pulp to the diet may help to reduce the problem.
Other silage than grass silage
Alfalfa silage is comparable to grass silage. The ensiling process requires some support because of the higher protein content and the elevated puffer capacity of alfalfa compared to grass.
Grass and alfalfa silage offer the remarkable advantage to substitute hay while other types of silage contribute partly to the fibrous feeds in the ration. Corn silage, also available as bale silage or packed in sacks, is higher in energy than grass silage. This silage is interesting as feed for economic reasons but it requires protein supplementation. Research indicates enforced microbial activity when feeding corn silage. The consequence is an additional need for heat export, which is reflected by stimulated sweat production. Research work is necessary to clarify those effects of corn silage more precisely.
Other types of silage like ensiled sugar beet leaves, potato silage etc. are also used for horses but play no role in regular feeding regimes. Pressed sugar beet pulp silage is been promoted as an important feed for ruminants. In horses, this silage show low palatability and is obviously less suitable than dried sugar beet pulp.
Literature
Kamphues, J. (2005): A systematic approach to evaluate the hygienic quality of feedstuffs for horses.
Proceedings Equine Nutrition Conference, Hannover, Pferdeheilkunde 21, 15-18
Müller, G. (2002): A field study into the nutritional intake of horses fed grass silage or hay as roughage including factors influencing faecal consistency. Thesis, Univ. Vet. Med. Hannover
Wolf, P., M. Coenen, J. Kamphues (2005): A survey on the hygienic Standard of feed for horses associated with diseases.
Proceedings Equine Nutrition Conference, Hannover, Pferdeheilkunde 21, 24-25
