Feed value and feeding of wastelage made from distillers grain solubles, pig slurry solids and ground straw treated with urea and NaOH

Urea at five levels (0, 1, 2, 4 and 6%) and NaOH at two levels (2 and 4% of dry matter to each of 2 and 4% urea level) were added to a mixture consisting of seven parts distillers grain solubles, two parts pressed pig slurry solids and one part ground wheat straw, on a fresh weight basis.

After a fermentation period of 42 days at ambient temperature in 100-litre capacity silos, the pH dropped in the unsupplemented wastelage (3·90), but it increased after urea and NaOH supplementation (up to 7·14). Ammonia and acetate concentrations in wastelage were enhanced with urea addition. Increase of acetate and butyrate concentration was observed when NaOH was added.

In sacco degradability increased from 49·0% (untreated sample) to 67·0% when 2% urea and 4% NaOH were added. The rumen dry matter degradability of wastelages was significantly higher when sheep consumed a diet rich in roughages (57·5%) rather than a concentrate ration (50·1%). Sheep consumed about 1 kg dry matter daily when unsupplemented or when 1% urea-added wastelage was fed. Higher levels of chemicals decreased dry-matter intake.

Chemically-treated wastelage replaced about a half of wilted grass silage without any negative effect on daily weight gain in short-term feeding experiment with growing bulls.