Aerobic exposure of lucerne silages and its impact on preference and dry matter intake by goats

The aim of this study was to determine the effect of aerobic exposure of lucerne (Medicago sativa L.) silages on short-term dry matter intake (DMI) and preference by goats. Third-cut lucerne was harvested at late-bud stage and, after field-wilting, ensiled either untreated (CON) or treated (IRE) with a chemical additive containing sodium nitrite and hexamine. Each treatment was ensiled in a separate round bale. After 5 months, both round bales were opened, each silage mixed thoroughly and exposed to air for 8 days (d). In 2-d intervals, silages were sampled for chemical and microbiological analyses (yeasts, moulds and aerobic mesophilic bacteria) and stored anaerobically in vacuum-sealed polyethylene bags for use in feeding trials. For both silages, one preference trial was done with Saanen-type wethers (n = 5), each one lasting 15 d. During the experimental phase, each possible combination of two silages (n = 10) was offered to the goats as free choice for 3 h. Data were analyzed using SAS with an analysis of variance, and correlation analysis between silage characteristics and DMI. At opening, concentrations of lactic, acetic, and butyric acids were 39,25 and 2.5 g/kg DM in CON (401 g DM/kg), and 31, 12 and <0.02 g/kg DM in TRE silages (385 g DM/kg). During aerobic exposure, mould counts in CON increased, but silage temperature remained stable. The TRE silage heated (>3.0 degrees C above ambient) on d8, possibly due to higher amounts of water-soluble carbohydrates and increasing yeast counts. In both trials, goats showed a strong avoidance for aerobically exposed silages. The 3-h DMI (n = 20) for d0-silage was 700 g (TRE) and 670 g (CON), it decreased on d2 (TRE) and d4 (CON) of aerobic exposure (P < 0.001). On d8, there was a decline (P < 0.001) in DMI of 67% (CON) and 58% (TRE) compared to d0-silages. Aerobic exposure of lucerne silage strongly influenced preference and short-time DMI by goats, although silage temperature, fermentation products and microbial variables changed only slightly. (C) 2014 Elsevier B.V. All rights reserved.