Shorter cutting length slightly enhances nutrient retention and fermentation efficiency of heavily wilted Italian ryegrass silage

Abstract

This study evaluated the effects of different theoretical lengths of cut on nutrient preservation and fermentation kinetics of low-moisture Italian ryegrass (approximately 80% dry matter [DM]). After harvest, the forage was field-wilted for 2 days and then manually chopped to 10, 20, or 30 mm for ensiling, and silage samples were collected on Days 1, 2, 3, 5, 10, 20, 30, 45, and 60. During fermentation, DM content initially decreased and subsequently increased, resulting in a slight increase for the 10-mm group but a significant decrease for the 30-mm group (from 84.06% to 78.88%, p < .05). Structural carbohydrate concentrations increased after ensiling, with both neutral detergent fiber (NDF) and acid detergent fiber (ADF) showing significant elevations across treatments. The most pronounced increase occurred in the 30-mm group, particularly for NDF (from 69.45% to 75.71%, p < .01). CP content in the 20-mm group was significantly lower than that in the 10- and 30-mm groups (p < .01), whereas in vitro dry matter (DM) digestibility remained relatively stable and did not differ among treatments. Fermentation patterns were similar across groups, as pH and water-soluble carbohydrate (WSC) contents declined only slightly throughout ensiling. However, during the early fermentation stage (first 10 days), the 10-mm group exhibited a relatively rapid decline in pH, reaching 6.16. Accordingly, lactic acid accumulation was significantly higher in the 10- and 20-mm groups (0.84% and 1.40% DM, respectively) than in the 30-mm group (0.46% DM, p < .01). By the end of ensiling, the 10-mm treatment achieved the highest TDN level. Overall, shorter theoretical lengths of cut promoted early lactic acid fermentation and more effective acidification in heavily wilted forage. Therefore, reducing cutting length to approximately 10 mm is recommended to improve the fermentation quality of low-moisture Italian ryegrass silage.