THE DIGESTIBILITY AND ENERGY VALUE OF BADLY PRESERVED GRASS SILAGES

The results of a study into the chemical composition, digestibility an d energy value of nine badly preserved silages are reported. Digestibi lity and energy values were measured in vivo using four wether sheep p er sample fed at near to maintenance. The silages studied had low tolu ene dry matter (TDM) contents (208 +/- 21.8 g kg-1) and high concentra tions of n-butyric (35 +/- 10.4 g kg-1 TDM) and acetic acid (31.7 +/- 7.9 g kg-1 TDM) together with high ammonia nitrogen concentrations (36 4 +/- 185.3 g kg-1 total nitrogen). These values in association with h igh pH values (5.1 +/- 0.51) confirmed the badly preserved nature of t he silages. Digestible organic matter contents of the TDM in vivo (645 +/- 66.9 g kg-1) and metabolisable energy contents using predicted me thane losses (9.1 +/- 1.70 MJ kg-1 TDM), whilst not a direct compariso n, covered a range similar to that observed in an earlier study of mai nly well-fermented silages. For seven silages where methane energy los ses were measured (0.061 +/- 0.0102 of gross energy (GE)) values were significantly (P<0.01) lower and more variable than when predicted (0. 078 +/- 0.0042 of GE) by a commonly used relationship.