Variation in nutritive value of plant parts of subterranean clover (Trifolium subterraneum L.)

Abstract

While it has been reported that leaves of subterranean clover are less digestible than stems, there is a lack of information on the variability of nutritive value of plant parts of subterranean clover. To determine the variation in nutritive value of leaf, petiole, stem and burr, an experiment with 26 cultivars of subterranean clover was conducted at Shenton Park Field Station, Perth, Western Australia. The cultivars were divided into 3 maturity groups according to flowering time and each cultivar was sown in blocks comprising 4 replicates. The plots were grazed by sheep at 2-weekly intervals. Plants were sampled at the vegetative stage before grazing and after the cessation of flowering. Dry matter digestibility (DMD) and nitrogen concentration of leaves, petioles, stems and burrs were determined. At the vegetative stage, there was no difference in DMD (P>0.05) among plant parts for most cultivars, and leaf had the highest (P<0.05) nitrogen concentration (4.8–5.4%). After the cessation of flowering, leaf had the highest DMD and nitrogen concentration (P<0.05). The DMD of plant parts differed significantly among cultivars (P<0.05). There was a slight decrease in DMD over time for leaves and a significant decrease in DMD for stems and petioles. These results suggest the main objective of grazing management of subterranean clover swards should be to increase the proportion of leaf material in the swards and that selection of leafy varieties by breeding could improve the late season digestibility of subterranean clover. Such management and breeding strategies would have value when the cultivars are in mixed pastures or used with supplements in summer.