Treatment of whole-crop cereals with alkali. 1. The influence of sodium hydroxide and ensiling on the chemical composition and in vitro digestibility of rye, barley and wheat crops harvested at increasing maturity and dry matter content

Abstract

Whole crops of rye, barley and wheat were each cut at three stages of maturity and dry matter (DM) content, and were ensiled in polythene bag silos directly or after wilting to ∼ 600 g DM kg −1, with (50 g kg −1 DM) or without the addition of “pearl” sodium hydroxide (NaOH). Fourth cuts of barley and wheat were ensiled directly, with or without NaOH, when their DM content reached ∼ 600 g kg −1. With advancing maturity, the DM contents of crops increased. For rye, the contents of water-soluble carbohydrate (WSC) and starch also increased, although the level of starch was low. In contrast, the WSC in the more mature barley and wheat crops decreased as starch increased. There was a general trend for nitrogen content to fall, most markedly for rye. For all crops, WSC was lost and organic matter digestibility fell during wilting. In silages made from young crops (< 400 g DM kg −1), WSC and pH were low and products of fermentation high. In high DM silages, there were reduced contents of lactic acid, ethanol and ammonia. Treatment of the crop with NaOH raised the pH and the proportion of hot-water-insoluble nitrogen in all silages and tended to enhance the effect of DM on organic acid production. Organic matter digestibility of the crops was always higher than in the corresponding untreated silage. The response to NaOH improved as the crops matured, resulting in increases of up to 6 percentage units for Cut 1 and of between 15 and 20 units for the later cuts. With the relatively low DM rye silages, wilting improved the effect of NaOH by up to 9 units. It is concluded that whole-crop cereals, directly harvested at ∼ 600 g DM kg −1, can be effectively preserved and upgraded by ensilage with 50 g NaOH kg −1 DM. At this maturity, crop yields are close to maximum and the potential nutritive value of the upgraded material is high.