Digestibility and voluntary intake measurements on regrowths of six Tasmanian pasture species

Abstract

Pure species swards of Trifolium repens (white clover cv. Grasslands Huia), Lolium perenne (perennial ryegrass cv. Tasmanian No. I ) , Lolium perenne x L. multiflorum (short rotation ryegrass cv. Grasslands Manawa), Lolium perenne (long rotation ryegrass cv. Grasslands Ariki), Dactylis glomerata (cocksfoot cv. Currie) and Dactylis glomerata (cocksfoot cv. Grasslands Apanui) were mechanically cut in May, August, September-October, and November 1969, and January, March, May, and August 1970. The material from these cuts was artificially dried, and digestibilities and voluntary intakes measured using penned sheep. Overall, the digestibility and voluntary intake of white clover was significantly higher (P < 0.05) than that of any of the grasses, the digestibility of Apanui cocksfoot was significantly lower (P < 0.05) than that of the ryegrasses and there were no significant differences (P < 0.05) between the intakes of the various grasses. Under the management system used, the digestibility of the grasses remained relatively stable over the summer, autumn and winter, rose to a peak in early spring and fell in late spring after ear emergence. The digestibility of white clover remained high over the winter and early spring and declined slowly over the summer. The voluntary intakes of all the species were at their lowest levels in the winter, rose to a peak in the spring, fell in the late spring to a stable level over the summer, and fell again in the autumn. At any digestibility level, the intake of spring-summer cut pasture was approximately 20 per cent higher than that of winter cut pasture. The intake of autumn cut pasture was intermediate. The overall relation between intake (I) and digestibility (D) was I = 1.06D + 2.7 ¦ 8.4 (P < 0.01). Within the spring-summer cuts, the relation was I = 1.01 D + 14.6 ¦ 4.0 (P < 0.01) and within the winter cuts it was I = 1.08D - 5.9 ¦ 4.1 (P < 0.01).