A calorimetric investigation of the nutritive value of formic acid- and formaldehyde—Formic acid-treated grass silages

Experiments were conducted to study the utilisation of a ryegrass mixture preserved chemically by formic acid (silage 1) of mean gross energy (GE) 18.6 MJ/kg dry matter (DM), and formaldehyde—formic acid (silage 2) of mean GE 18.3 MJ/kg DM. The parent grass and resulting silages were analysed chemically and calorimetric balance trials were performed with four sheep fed at maintenance and 1.5 times maintenance.Silages 1 and 2 had similar, high digestibility coefficients for DM (0.732 and 0.718), organic matter (OM) (0.755 and 0.742), and energy (E) (0.730 and 0.710). The digestible energy (DE) contents of silages 1 and 2 were 13.3 and 12.7 MJ/kg DM, respectively, at the lower level of feeding and 13.8 and 12.8 MJ/kg DM, respectively, at the higher level. The metabolisable energy (ME) contents of silages 1 and 2 were 11.6 and 10.8 MJ/kg DM, respectively, at the lower level of feeding and 12.0 and 11.0 MJ/kg DM, respectively, at the higher level.The mean efficiency of utilisation of ME for growth (K_g) for silages 1 and 2 was 0.43 and 0.39, respectively; these results are in broad agreement with those predicted by other workers.