Intake characteristics of perennial ryegrass varieties when grazed by yearling beef cattle under rotational grazing management

Abstract

Four intermediate-heading perennial ryegrass (Lolium perenne L.) varieties, which in previous studies had been associated with high-or low-intake characteristics when swards containing them had been continuously stocked with sheep, were sown as monocultures. They were rotationally grazed, using 1-d paddocks, with core groups of four yearling Simmental · Holstein beef heifers in 2002 and 2003 and ingestive and ruminative behaviour, and sward factors, were measured. There were two diploid (Belramo and Glen) and one tetraploid (Rosalin) perennial ryegrass varieties and one tetraploid hybrid (Lolium · boucheanum Kunth) (AberExcel) variety. Intake rate (IR) was significantly higher in August 2003 for heifers grazing Glen than those grazing Belramo [27AE5 vs. 20AE6 g dry matter (DM) min )1 ; P ¼ 0AE019], but there were no significant differences between varieties in two other measurement periods. This is in contrast to previous results with sheep when IR were significantly higher for Glen than Belramo and for AberExcel than Rosalin. Total jaw movement rates during grazing were significantly higher for heifers on the tetraploid swards than those on the diploid swards (87AE7 vs. 83AE6 jaw movements min )1 ; P ¼ 0AE023) in September 2002. Ruminating time was significantly lower for heifers on the tetraploid swards than those on the diploid swards (453 vs. 519 min 24 h )1 ; P ¼ 0AE012) in July 2002. Digestibility of grass snips was significantly higher on the tetraploid than the diploid swards [697 vs. 680 g digestible organic matter (DOM) kg )1 DM; P ¼ 0AE042] in September 2003 and, within diploids, was significantly higher for Glen than Belramo (696 vs. 663 g DOM kg )1 DM; P ¼ 0AE014). There were significant differences in sheath tube and leaf lengths and in the population density of tillers between and within ploidies, which might have been expected to have influenced intake characteristics, but this was not generally found under rotational grazing with cattle. In order to separate the effects of defoliation interval from those of grazing style of the different ruminant species, it is suggested that grass variety evaluations using continuously stocked cattle swards are required.

Use of a micro-sward technique for determining bite mass of four grass species in short-term tests

“…Orr et al (2005a) developed a low-cost, short-term method of assessing bite mass of different perennial ryegrass cultivars and demonstrated that differences observed at the micro-sward box level were correlated with those found in the field (Orr et al 2005b). While this methodology has been conducted and reported in the literature, further studies of this kind are justified to broaden the range of forage species studied.…”

“…Specifically, the generality of drivers of grazing behavior across forage species needs to be tested. Therefore, the aim of this study was to characterize bite mass of cattle in relation to morphological traits of grass species typically found in semi-natural pastures in the UK following the methods of Orr et al (2005a).…”

Cultivar Effects of Perennial Ryegrass on Herbage Intake by Grazing Dairy Cows

“…Gowen et al (2003) found an effect on daily intake by grazing dairy cows and showed that late-heading perennialryegrass cultivars might have better potential than intermediate-heading cultivars. Orr et al (2005) did not find differences in grazing beef cattle among four perennialryegrass cultivars for any behavioural aspects, such as intake rate, biting rate, chewing rate and total jaw movement rate. Lee et al (2002) found an effect on intake of growing steers of a cultivar with increased water-soluble-carbohydrates concentration.…”

“…However, these differences were found in projects screening large numbers of perennial ryegrass cultivars. In studies with fewer cultivars (O'Donovan 2001; Barrett et al 2003;Orr et al 2005), no significant differences between the diploid cultivars were found. The differences in sward surface height were most prominent in spring and early summer, whereas in the vegetative stage they were generally not larger than 3-4 cm.…”

“…In several studies in the last decade, the effect of perennial-ryegrass cultivars on herbage intake characteristics has been investigated (Munro et al 1992;Hazard et al 1998;Casey and Brereton 1999;Gowen et al 2003;Orr et al 2003;Barrett et al 2003;Orr et al 2005;Smit et al 2005b;Tas et al 2005). The intake of herbage by grazing herbivores could be divided into several characteristics that are important: daily intake, intake rate, bite mass, bite number or biting time and bite volume.…”