DIGESTIBILITY BY SHEEP AND PERFORMANCE OF STEERS FED SILAGES STORED IN TOWER SILOS AND SILO PRESS BAGS

Abstract

This experiment evaluated the effect of type of silo on fermentation characteristics, digestibility of single and mixed silages by sheep, and growth performance of steers fed mixtures of corn silage (C) and grass silage (G) at a 1:1 ratio of dry matter (DM). The grass silage (60% alfalfa: 40% grass) harvested at 48% DM and corn silage harvested at 32% DM were stored both in tower silos (TS) and silo press bags (SPB). In each case, on the day of filling, thermocouples were imbedded at different places along the silos. Fermentation temperature of silage stored in SPB dropped more rapidly (P < 0.05) than that of TS after reaching maximum temperature. For the single silages (GST, GSPB, CTS and CSPB) maximum temperatures were 43, 42, 24 and 22 °C, respectively. The single silages and their mixture (GTS + CTS, GSPB + CSPB, GTS + CSPB and GSPB + CTS) were fed to sheep according to a double 4 × 4 Latin square design. Concurrently, 72 Hereford steers weighing 190 kg average live weight were allotted to 12 groups each of six steers and fed four silage mixtures ad libitum according to a complete block design in three replications during 196-day period. Within plant species, type of silo had no effect (P > 0.05) on pH values and silage chemical composition. Voluntary DM intakes were 67.0, 69.4, 49.4 and 46.2 g/kgW0.75 for GTS, GSPB, CTS and CSPB, respectively. No significant differences (P > 0.05) were noted between intake of silages fed as mixtures. Digestibility coefficients of grass silage DM, crude protein (CP) and acid detergent fiber (ADF) were 7.5, 13.8 and 5.5% higher (P < 0.05), respectively, for GSPB than GTS. However, there were no significant differences between digestibility coefficients of corn from SPB and TS. Better DM and CP digestibilities (P < 0.05) were obtained when GSPB was fed in mixture with corn than GTS in mixture with corn. Average daily gain of steers was higher (P < 0.01) with GSPB (0.79 kg/day) than with GTS (0.73 kg/day) fed in mixtures with corn silage. Key words: Silo press bags, tower silos, silage composition, sheep digestibility, steer performance