The effect of calcium and sodium hydroxides and of sodium acrylate on the fermentation and digestibility in vitro of ensiled whole-crop wheat and barley harvested at different stages of maturity

Abstract

Whole-crop wheat and barley were each harvested at the soft-, medium- and hard-dough stages of grain development. Material from each harvest was ensiled in polythene bag silos without additive or after the addition of calcium hydroxide, sodium hydroxide or sodium acrylate at 50, 50 and 12.5 g kg −1 of the crop dry matter (DM), respectively. All silages were opened after 60 days. With advancing maturity there was an increase in the content of DM, starch and insoluble-nitrogen, but a reduction in water-soluble carbohydrates (WSC) and ash. When crops were ensiled without additives, only medium-dough barley fermented to give butyric acid. However, the addition of calcium hydroxide to crops of low DM (soft-dough) and medium DM (medium-dough) promoted the activity of clostridial bacteria giving rise to the production of butyric acid, but this did not occur with crops of high DM (hard-dough). Sodium hydroxide gave rise to butyric acid only at low DM, and to restricted fermentation at high DM content. Sodium acrylate restricted fermentation and prevented butyric acid production in all silages. Ensiling led to an average reduction of 5 percentage units in the digestible organic matter (DOM) of the control silages compared to that of the crops. Addition of calcium hydroxide and sodium acrylate gave values similar to the control silages. Only sodium hydroxide consistently increased DOM, the effect becoming more marked as the crops matured. The increases over the control silages were 10, 18 and 26 units for wheat and 15, 21 and 20 units for barley at low, medium and high DM, respectively.