Perennial ryegrass cultivar effects on intake of grazing sheep and feeding value

The use of animal trials in routine evaluation of grass cultivars under grazing is expensive and space-and time-consuming. Therefore, there is a need to find cultivar morphological traits enhancing animal production under grazing which could be used to evaluate and breed grass cultivars. The morphogenesis of four cultivars of perennial ryegrass (Lolium perenne L.) was compared in relation to their intake by grazing sheep. Sheep intakes were estimated by following the consumption of marked tillers over 4 days of grazing, after 3, 4 and 5 weeks of growth and at the same allowance of 1.7 kg DM day(-1) sheep(-1). Significant differences in intake were found between cultivars but the order was management-dependent. Intake under grazing was positively correlated with the green lamina mass above 10 cm. The same cultivars were fed to sheep in individual crates. Ingestibility, in vivo digestibility and palatability were assessed and significant differences were found between cultivars. Ingestibility was positively correlated with the lamina to pseudostem ratio, while digestibility was negatively correlated with the quantity of dead leaves in the fresh forage. No correlations were found between the intake under grazing and ingestibility, in vivo digestibility and palatability measured with the housed animals. The potential value of perennial ryegrass cultivars under grazing can not be drawn from the feeding value assessment with housed animals. Green lamina mass could be a good trait to assess in an evaluation process of grass cultivars and to select for since it seems to be related to the potential intake by grazing sheep at a given management. ((C) Elsevier/Inra).