Energy and nitrogen balance,intake and growth rate of lambs fed on unwilted grass silages treated with a formaldehyde—Acid mixture or untreated

Wether lambs were fed on precision-chopped first-cut ryegrass silage ad libitum in an intake trial, and a maintenance and 1.5 times maintenance in balance trials.The untreated and treated silages had pH values of 4.72 and 4.40, mean dry matter (DM) contents of 176 and 184 g kg^?1 and mean gross energy (GE) contents of 18.8 and 19.0 MJ/kg DM, respectively.Mean digestibility coefficients of DM (0.787 and 0.783), organic matter (OM) (0.827 and 0.820) and GE (0.794 and 0.793), for the treated and untreated silages respectively, were high. The metabolisable energy (ME) contents of the untreated and treated silages were 12.52 and 12.76 MJ/kg DM at maintenance and 11.94 and 12.56 MJ/kg DM at 1.5 times maintenance, respectively. The mean efficiency of utilisation of ME of the untreated and treated silages was 0.65 and 0.66 for maintenance (k_m) and 0.34 ± 0.134 and 0.40 ± 0.069 for growth (k_g), respectively; the k_g values were lower than expected.Dry matter intakes of these silages when given ad libitum were 27.9 and 28.8 g/kg W per day and produced live weight gains of 129 and 140 g day^?1 for the untreated and treated silages, respectively. These gains were similar to predicted values for live weight gain only when the experimentally determined k_g and k_m values were substituted in the equation of the Agricultural Research Council (1980) used for calculating the daily metabolisable energy requirements for live weight gain.