EFFECTS OF PRESERVING ALFALFA FORAGE AS FORMIC-ACID-TREATED SILAGE, WILTED SILAGE, AND AS HAY IN LARGE ROUND BALES ON CHEMICAL COMPOSITION, RECOVERY OF NUTRIENTS, DIGESTIBILITY AND HEIFER GROWTH

Abstract

First-cut alfalfa was stored as formic-acid-treated silage (FS), wilted silage (WS) and hay (Hay 1) in large round bales (LRB). Hay 1 was exposed to frequent showers (15.1 mm) in the windrows and required a drying period of 13 days; dry matter (DM) yield was only 60% of the average for silages (3.9 tonnes/ha). Second-cut alfalfa hay (Hay 2) yielded 1.84 tonnes DM/ha. For winter feeding, recoveries from storage of FS, WS, Hay 1 and Hay 2, respectively, were 85.7, 87.2, 78.3 and 81.9% of energy; 81.1, 87.0, 75.0 and 72.6% of crude protein (CP). Adlibitum intakes of DM were 1.90, 1.93, 1.78 and 2.08% of body weight for the four treatments, respectively. Differences in chemical composition and digestibility of nutrients for FS, WS and Hay 2 were small and statistically not significant (P > 0.05). However, values of FS were highest for CP (20.6%) and gross energy (20.5 kJ/g DM); digestibilities of DM, energy and CP (i.e. 59.3, 60.6 and 68.7% respectively) when fed at maintenance level; digestibilities of DM, energy, CP, cellulose and hemicellulose (i.e. 64.1, 66.6, 61.9, 64.5 and 46.3%, respectively) when fed in combination with corn silage (1:1 DM basis) on an ad libitum basis. All these values were significantly (P < 0.05) higher than the corresponding values for Hay 1. Heat damage to CP of hay stored in LRB was high and 19.9% of total N of Hay 1 was in the acid detergent insoluble fraction. In a growth study, performance of yearling heifers did not differ significantly when rations made of corn silage and FS or WS (1:1 DM basis) were compared. Key words: Alfalfa silages, wilted, digestibility, formic acid, round bales, heifer growth