Ensiling and evaluation of forage crops: effects of harvesting strategy and use of additives to fresh-cut and wilted crops
1997
Laettemaee, P. (SLU, Uppsala (Sweden). Inst. foer Husdjurens Utfodring och Vaard)
The aim of this thesis was to study the conservation and storage of high quality forage crops as silage, emphasizing the influence of additives to fresh-cut and wilted crops. The nutritive value of the forage was greatly influenced by the species, the time of the first harvest and cutting frequency during the season. A reasonable first harvesting time and three cuts per season generally seemed to be suitable as this combines a good nutrient concentration with satisfactory nutrient yields. The silage quality of direct-cut herbage without using additives was variable. The results showed that legumes were easily ensiled. There were also indications that other substances than water soluble carbohydrates were used as energy sources during fermentation. The use of additives improved silage quality both in unwilted and wilted crops. Application of sodium benzoate in combination with hexamine in direct-cut herbage reduced clostridial activity and protein deamination. Molasses and formic acid, applied either separately or in combination in direct cut red clover, improved fermentation, whereas molasses also increased the nutritive value of silage. A combination is preferred to avoid an over-fermented silage and because molasses reduces the volatility of formic acid. However, effluent losses may be substantial if molasses is applied to low DM herbage. Wilting over 300 g DM kg-1 showed improvements in silage quality under optimal fermentation conditions. Ensiling of long-cut wilted crops resulted in clostridial fermented silage with high spore counts under stressed fermentation conditions. The activity of yeasts was also enhanced in wilted silage. Yeasts seemed to be responsible for the rapid aerobic deterioration of silage. To ensure a high hygienic silage quality without effluent losses, both wilting and use of an appropriate silage additive are recommended. Application of hexamine and sodium nitrite with salts of organic acids effectively reduced both the clostridial and fungal activity and resulted in good storage stability.
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