THE EFFECT OF HARVESTING BEFORE AND AFTER FROST ON CORN SILAGE COMPOSITION, AND ITS INTAKE AND DIGESTIBILITY IN SHEEP

Abstract

Early-maturing forage corn (Zea mays L.), DK-22, was harvested in Prince Edward Island twice, 3 and 6 wk before the occurrence of the first killing frost, and twice again, 2 and 4 wk after the first killing frost, and ensiled during each of the three experimental years. Each silage was fed to six sheep in order to measure voluntary intake and digestibility. Magnesium content was severely reduced by ensiling fresh forage from prefrost harvest. The postfrost silages were drier and higher in pH than the other silages. Detergent fiber levels were lower in the prefrost than in the postfrost silages (P < 0.05). Intake was slightly higher for prefrost silages and this was significant in the third year (P < 0.05). The depression in digestibility between prefrost and postfrost silages was highest for nitrogen. Using digestible dry matter intake as a measure of feed value, the silage harvested in mid-September was assigned a relative feed value of 100, and by comparison, the two postfrost silages were 16 and 34% lower in feed value, respectively.Key words: Relative feed value, forage quality, frosted crop