Effects of dry-matter content on the nutritive value of individually wrapped round-bale timothy silage fed to sheep

Abstract

Thirty-two sheep (30.0 kg avg. BW) were used to study the effects of dry-matter (DM) content at harvest on the nutritive value of timothy grass silages conserved as round bales of high (52.1%, DM50), medium (39.9%, DM40) and low (23.1%, DM25) DM. Chopped grass of 24.4% DM conserved in a horizontal silo (HS) was used as a control. Gross energy, crude protein (CP) and acid detergent fibre (ADF) contents were similar for all silages (P > 0.05). Neutral detergent fiber (NDF) contents decreased as DM of the silages decreased (P < 0.05). Acid detergent lignin and ash contents were highest in HS and lowest in DM40 silages (P < 0.05). Silage pH and water-soluble carbohydrates decreased with decreasing DM of the silages (P < 0.05), while ammonia-N and lactate levels increased (P < 0.05). Acetate concentrations in round bales were lower than in HS silage (P < 0.05). Significant butyrate concentrations were detected only in DM25 silage. Round-bale silages were chopped before feeding and fed ad libitum. DM intake was 14.5% higher for DM50 and DM40 silages than for DM25 and HS silages (P < 0.001). Average daily gain and feed efficiency were higher for high-DM silages than for DM25 and HS silages (P < 0.01). Apparent digestibilities of NDF, cellulose and crude fiber of the silages were similar, but DM, organic matter, energy and hemicellulose digestibilities were higher for HS than for DM25 silage. Apparent digestibilities of ADF and CP were higher for high-DM silages than for DM25 and HS silages (P < 0.04). The results indicate that to obtain good-quality silage, the DM content of round bales should be 40–50%. The better performance obtained with high-DM silages was indicative of a more efficient utilization of metabolizable energy for gain. Key words: Round-bale silage, timothy, forage