INFLUENCE OF CARBOXYLIC SALTS ON SILAGE CONSERVATION, AND VOLUNTARY INTAKE AND GROWTH OF STEERS GIVEN LUCERNE SILAGE

Three wilted silages (dry matter concentration of approximately 300 g/ kg) were prepared from early-bloom lucerne which received no additive (MG-0), or was treated with a mixture of carboxylic salts (Maxgrass) a t either 4 (MG-4) or 8 (MG-8) l/t fresh crop. Silages were stored in t ower silos. Resulting silages were offered ad libitum to growing Holst ein steers without supplementation. Untreated silage (MG-0) exhibited an extensive, predominantly lactic acid fermentation. The nitrogen (N) fraction was highly soluble, relative to the crop at ensiling. Silage fermentation and protein solublization were restricted by Maxgrass ap plication. Maxgrass application reduced aerobic stability of silage re moved from the upper third of silos but not of silage from the lower p ortion of silos. Apparent digestibility showed a quadratic response to level of Maxgrass application (P < 0.05). Voluntary intake was not af fected by Maxgrass addition (P > 0.005) but intake of all silages was high (30 g/kg live weight (LW)). There was a positive linear response (P < 0.05) in LW gain to Maxgrass application with gains of 0-74, 0.86 and 0.87 kg/day being achieved in steers given MG-0, MG-4 and MG-8 si lages, respectively. Degradability of silage N determined in nylon bag s in situ was unaffected by Maxgrass application. However, the immedia tely degradable N fraction was reduced by Maxgrass application (linear effect, P < 0.001; quadratic effect, P < 0.05). Benefits in animal pe rformance due to Maxgrass application were attributed to improved N co mposition while restricted carbohydrate fermentation during ensiling w as considered to be of secondary importance.