Silage and haylage for horses

This review covers current understanding on the use of wrapped forages such as silage and haylage as forage sources in equine nutrition. Silage (dry-matter content <500 g per kg) generally have higher concentration of lactic acid and other fermentation products and has a lower pH compared to haylage (dry-matter content >500-840 g per kg), as the lack of water in haylage restricts fermentation. The differences in biochemical and microbial composition in forage conserved as silage, haylage and hay have not been reported to influence digestion or hindgut function in horses differently. Studies on equine intake and preference of forages conserved as silage, haylage or hay are scarce and contradictory; both low voluntary intake and preference for silage have been reported. Studies on aerobic storage stability of opened bales are few, but are needed, as daily forage consumption is often low on horse farms, which may increase the risk of aerobic deterioration of forage in opened bales before they have been fed. A high hygienic quality of wrapped forages for horses is crucial: (a) as mould spores may cause chronic respiratory disorders; (b) as mycotoxins may cause intoxications, skin problems, gastrointestinal disorders and reproduction failures; (c) as presence of Clostridium botulinum and its toxin botulin may cause fatal disease; and (d) as other microbes (e.g., Listeria monocytogenes) may cause illness in the horse. Further research is needed especially for systems of assessment of hygienic quality of haylage, and how to prolong aerobic storage stability in opened bales.