The influence of nitrogen and defoliation on digestibility and fibre content of Lolium multiflorum cv. Midmar

Abstract

The influence of different N fertiliser application levels (0, 150, 300 and 450kg N ha^–1) in combination with different defoliation intervals (every 2, 4, 6 and 8 weeks and twice a season) on the digestibility and fibre component of ryegrass (Lolium multiflorum) cv. Midmar was investigated. Organic Matter Digestibility (OMD), Neutral and Acid Detergent Fibre (NDF and ADF) were determined. OMD, NDF and ADF content were significantly (P < 0.01) influenced by N level, defoliation interval and the interaction between these two factors. Nitrogen level had a lesser influence on OMD, NDF and ADF than defoliation interval, because defoliation interval exerts a greater influence on plant growth stage and maturity than N level. Increased N levels and lengthening the defoliation interval decreased (P < 0.05) OMD. With defoliation intervals of four weeks and shorter, increased N levels resulted in decreased NDF and ADF content, but six weeks and longer intervals resulted in the opposite. It is essential to assess OMD and fibre content as part of the pasture nutritive characteristics when evaluating a planted pasture as it will contribute to the understanding of pasture manipulation for sustainable animal production.