Laboratory evaluation of ensiled mixtures of alkali-treated cattle excreta and whole-crop maize

Faeces or manure (faeces + urine + straw bedding) from beef cattle given maize silage diets were ensiled with whole-crop maize (27% dry matter), after treatment with NaOH at 0, 7.5 or 15 g per 100 g excreta DM, so that excreta DM comprised 25, 50 or 100% of the total DM, in a factorial design. A control treatment consisted of maize forage ensiled alone. The ensiled products were analysed for the content of fermentation acids, pH, nitrogenous compounds, structural carbohydrates, starch, water-soluble carbohydrates, ash, sodium and digestibility in vitro. Mixtures which contained 25% excreta DM were well preserved with relatively low values for pH, butyric acid and ammonia-N, and a high proportion of fermentation acids as lactic acid. Mixtures which contained 50% excreta DM were generally poorly preserved. Addition of NaOH to excreta prior to ensiling was reflected in a decrease in the content of neutral detergent fibre and increased digestibility of organic matter in vitro in the ensiled products. Mixtures of 25% excreta treated with 15 g NaOH/100 g excreta DM gave values for digestibility in vitro similar to that of the maize ensiled alone.