Changes During Growth in Cell Wall Components of Berseem Clover Under Different Cutting Treatments in a Mediterranean Region

Forage digestibility of berseem clover (Trifolium Alexandrinum L.) is influenced by plant cell wall composition. This study was conducted to evaluate the effects of different cutting treatments on cell-wall components of the herbage and plant fractions in two Mediterranean berseem genotypes during growth and to examine the relationship between digestibility and cell wall components in these plant fractions. Cutting treatments were initiated at sixth internode elongation (A) and early flowering (B) and there was an uncut control treatment (C). Spring growth of genotypes of Egyptian (cv. Giza 10) and Italian (cv. Sacromonte) origins was harvested in each of two years beginning 196 days after sowing and thereafter every 6 days (twelve harvests in total) to measure cell wall components. Neutral detergent fibre (NDF), acid detergent fibre (ADF) and acid detergent lignin (ADL) concentrations were determined for leaf, stem, and total forage of each cultivar at each harvest. Without defoliation, NDF, ADF and ADL concentrations of herbage increased linearly to a maximum of 528, 375 and 84 g kg-1 DM, respectively, by 220 days after planting, when plant height reached maximum values, then plateaued until 257 days after planting. Plant parts differed in cell-wall concentration, with stems being of higher fibre components than leaves, in the two cutting treatments. Herbage and plant fraction fibre concentrations were negatively correlated with digestibility for all cutting treatments. Defoliation induced a reduction in fibre concentrations and plant height, although a rapid regrowth was observed after cutting, in both treatments A and B. However, delaying defoliation to the early flowering stage (B) increased fibre components concentrations both at cutting time and during the growing season and significantly reduced the regrowth height. Conversely, plants cut at the sixth internode elongation (treatment A) showed lower concentrations of fibre fractions than initiating cutting at early flower (treatment B). Therefore, harvest management in which cuts are applied at the stage of sixth internode elongation appears to be the most favourable for obtaining forage of lower fibre content in berseem clover grown in Mediterranean regions.