Published online by Cambridge University Press: 25 May 2016
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) at either 4 (MG-4) or 8 (MG-8) l/t fresh crop. Silages were stored in tower silos. Resulting silages were offered ad libitum to growing Holstein 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 application. Maxgrass application reduced aerobic stability of silage removed from the upper third of silos but not of silage from the lower portion of silos. Apparent digestibility showed a quadratic response to level of Maxgrass application (P < 0·05). Voluntary intake was not affected 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 silages, respectively. Degradability of silage N determined in nylon bags in situ was unaffected by Maxgrass application. However, the immediately degradable N fraction was reduced by Maxgrass application (linear effect, P < 0·001; quadratic effect, P < 0·05). Benefits in animal performance due to Maxgrass application were attributed to improved N composition while restricted carbohydrate fermentation during ensiling was considered to be of secondary importance.