Development of a micro-sward technique for determining intake characteristics of perennial ryegrass varieties

Abstract

Two diploid (Belramo and Glen), one tetraploid (Rosalin) and one tetraploid hybrid (Lolium× boucheanum Kunth) (AberExcel) intermediate-heading perennial ryegrass (Lolium perenne L.) varieties were sown in boxes (85×44×14 cm) to create micro-swards. Once established, these were defoliated at approximately 21-day intervals before being offered to individual yearling Simmental × Holstein beef heifers in short-term tests. Bite mass measured in these tests was compared with bite mass for groups of similar heifers which were rotationally stocked on the same four varieties. The boxes were weighed (± 0.1 g) before and after a period during which the heifers were allowed to take approximately 50 bites. The micro-sward methodology was developed in, 2002 and bite masses for Belramo, Glen, Rosalin and AberExcel, respectively, were 0.44, 0.46, 0.49 and 0.50 g DM bite−1 compared with 0.48, 0.49, 0.50 and 0.50 g DM bite−1 measured for rotationally stocked cattle. In 2003, the values for bite mass were 0.40, 0.41, 0.41 and 0.43 g DM bite−1 measured using sward boxes and 0.31, 0.41, 0.34 and 0.37 g DM bite−1 for rotationally stocked cattle. Whilst the rankings were similar within ploidy for the two assessment methods, there were no significant differences between the varieties. The micro-sward methodology provides a rapid, low-cost assessment method with a low seed requirement to screen for intake traits during breeding programmes and during variety evaluation. Now there is a need to develop further this methodology in order to allow small-scale simulation of other defoliation regimes, for example continuous stocking.