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-I sheep Significant differences in intake were found * Correspondence and reprints.

Genetic vadation in the feeding efficiency of maize genotypes was evaluated from experiments with dairy cows. Maize genotypes were chosen to represent a range of digestibilities from previous experiments with standard sheep.The vadation in milk yield observed with dairy cows fed genotypes with low or high digestibilities or energy values was about 1.0-2.0 kg per animal per day. Moreover, the range of vadation in body weight was about 10-30 kg during the 3 months ofthe experiments. Hybrids with similar energy values had a similar effect on milk yield, but the intake of each hybdd could be very different when they were fed to dairy cows, even if no difference in intake had been observed in sheep. The higher silage maize intake of 'DK265' was mostly converted into a body weight gain rather than an increased milk yield, probably because the milk yield potential of the animals was soon reached. It appeared that those hybrids whose predicted energy value from sheep measurements was low led to relatively low performances in cows. Dairy cow performances also appeared to be related to the enzymatic solubility values of the whole plants.For maize breeders, the prediction of hybdd efficiency in dairy cow rearing must include digestibility and ingestibility factors. The most important challenge for maize breeders now will probably be the adjustment of a criterion for predicting intake because the stover digestibility and the starch content can be predicted reliably with the use of NIRS calibrations.Maize is nowadays a major forage crop for dairy cattle, and more than 3 300 000 ha are cropped in the European Union for silage-making. Silage maize is used as an energy source and its low protein content is easily corrected with soya or sunflower cattle cakes, as well as lucerne pellets. For a long time, breeders and farmers relied on the assumption that a good grain maize was also the most suitable for silage. But genetic variation in digestibiUty and energy value has been clearly demonstrated among experimental and registered hybrids. As reported by Deinum et al. (1984), Dijkstra and Becker (1960) probably performed one of the first in vivo digestion trials with standard sheep in digestibiUty crates. DigestibiUty of organic matter (DOM) of observed silages ranged from 59.2 to 72.7%. Andrieu and Demarquilly (1974), Gallais et al. (1976), Deinum et al. (1984 and Barriere et al. (1991) reported similar results, but with a narrower range of variation. However, the last two studies also reported values for brown midrib {bm2>) maize hybrids, the DOM of which neared around 4 points more than the best normal maize silages. Variation in DOM, digestibility of crude fibre (DCF) and UFL was investigated with standard sheep on a much broader genetic basis, by Barriere et al. (1992) (where UFL is the INRA fodder energy unit for milk production (Jarrige 1988) equivalent to 7.11 MJ/kg DM). Observed values ranged between 65.1 and 73.5% for DOM, 44.0 and 62.2% for DCF, and 0.79 and 0.94 for UFL, when investigating early and medium-early register...

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This paper reports on the first results of feeding value experiments, assessed with sheep, of hybrids between tetraploid Italian ryegrass {Lolium multiflorum, 2/7 = 4.x = 28) and a progenitor of tall fescue, Festuca arundinacea var. glaucescens (2n = 4x = 28). Three hybrid populations resulting from either high, low or no selection for palatabihty were compared with a variety of Italian ryegrass as control and two varieties of the cultivated hexaploid (2« = 6x = 42) tall fescue, one of which had been selected for high palatability. On average, the hybrid populations were found to be as palatable as the improved tall fescue with voluntary intake (VI), in vivo digestibility of organic matter (DOM), and net energy expressed in fodder units for milk, similar to the best palatable tall fescue and to Italian ryegrass. However, selection for improved palatability among hybrids did not result in any further improvement of other traits, except VI in the hybrid selected for high palatabihty which significantly exceeded VI of Italian ryegrass. In conclusion, intergeneric hybridization between L. multiflorum and F. arundinacea var. glaucescens led to an immediate increase of feeding value compared with selection for palatability in tall fescue. However, to improve feeding value of hybrids further, similar selection for high palatability appeared questionable and possibly detrimental for other agronomic traits because of complicated inheritance in tetraploid L. multiflorum x F. glaucescens hybrids.

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