Extent of fermentation in the silo can, through effects on silage composition, have important consequences for milk yield and composition. However, a poor understanding of the relationships between the chemical composition and digestion characteristics of silage, and of the implications for nutrient supply, makes it difficult to predict performance and to formulate concentrates to complement silages of different types. The 2 experiments presented here were conducted to determine rumen fermentation patterns for a range of silages, representative of restricted or enhanced fermentation in the silo, when supplemented with concentrates containing a high proportion of either starch or digestible fibre.

In each experiment 8 rumen-fistulated sheep were used to compare 8 silages, each given with 2 concentrates. Each experiment was conducted as four 4x4 Latin squares, with 2 silages given with each concentrate in a single square. Silages 1-12 were prepared from perennial ryegrass swards, harvested within 2-5h of cutting, precision-chopped to a length of approximately 20 mm, and ensiled in bunker silos of 60- or 300-tonne capacity.