Effect of a mixture of salts of carboxylic acids on silage conservation, voluntary intake and growth rate of cattle fed grass silages

A mixture of carboxylic salts (CS) was used to restrict the extent of fermentation in predominantly grass silages. In trial 1, wilted annual ryegrass/red clover [292 g dry matter (DM) kg−1] was ensiled without additive or after application of 8 L carboxylic salts t−1 fresh forage at ensiling. After 5 mo storage in a plastic silo tube, silages were offered to growing Holstein steers ad libitum, either alone or with 2 kg barley d−1 for 70 d. Use of CS restricted the extent of carbohydrate fermentation and protein solubilization compared with the untreated silage. When fed to steers, CS-treated silage resulted in higher intakes and body weight (BW) gains. Barley supplementation increased total DM intake, but reduced silage intake. Feeding barley increased BW gain. Feed conversion efficiency was improved by CS in unsupplemented silages but not in supplemented silages. In trial 2, first-cut, wilted orchardgrass/red clover was ensiled at 283 g DM kg−1 either with formic acid (FA) at 2 L t−1 or CS at 3.5 L t−1 in bunker silos. The regrowth was ensiled at 304 g DM kg−1 either with FA at 4 L t−1 or CS at 5.3 L t−1 in heap silos. Both CS- and FA-treated first-cut silages underwent butyric acid fermentations. Both second-cut silages were well preserved. Relative to the FA treatment, CS had little influence on fermentation or protein solubilization of the ensiled grass. When fed to growing heifers, intake and BW gains were less for first-cut than second-cut silages. There was no effect of additive on DM intake or BW gain, but feed to gain ratio was better in heifers fed CS-treated than FA-treated silage for both cuts. Carboxylic salts were effective at restricting fermentation and protein solubilization in silage which was beneficial to animal performance. Key words: Grass, silage additive, carboxylic salts, growth, beef