Effect of inoculation on silage quality and performance of steers fed grass and cereal silages either alone or in combination

Abstract

Two first-cut silages were prepared from orchardgrass/white clover cut at the end of June and ensiled with or without a silage inoculant containing 1 × 10 CFU g−1Lactobacillus casei, L. plantarum, and Streptococcus lactis at an application rate of 1 × 10 CFU g−1 crop. A further two silages were prepared from whole-crop wheat cut in the third week of August and ensiled with or without the same silage inoculant at the same application rate. The objectives of the study were to evaluate the effectiveness of a silage inoculant on silage fermentation, silage quality and animal response. Although inoculation increased lactic acid bacteria numbers in grass at ensiling, there were few observed differences in fermentation characteristics of the silages. Silages were used in a 16-wk feeding trial with 48 steers (initial BW 267 kg). Control and inoculated silages were fed either as 100% grass silage, 50% grass and 50% wheat silage mixture (dry matter basis), or as 100% wheat silage. All steers received a barley/soybean meal supplement at 2 kg d−1 (as-fed basis). Overall, DM intake was similar in control and inoculated silages, but there was an interaction (kg d−1P = 0.051; g kg−1 BW, P = 0.037) between crop and inoculant use indicating that intake was increased by inoculant use in grass silages only. Body weight gain was improved by 10% when inoculant was used (P = 0.006). This resulted in improved feed efficiency in wheat silage treated with inoculant (interaction, P = 0.023). Body weight gain decreased linearly as the proportion of wheat silage in the diet increased (P < 0.001), irrespective of inoculant use. Apparent digestibility of DM and components determined in sheep was higher for grass than wheat silage (P < 0.05), but there was no effect of inoculation on digestibility of either crop type. In this study, the application of inoculant to grass silage improved intake, while its application to wheat silage improved efficiency of feed utilization. Key words: Steer, inoculant, gain, grass silage, wheat silage