FIRST IN-VIVO ASSESSMENT OF FEEDING VALUE OF FESTULOLIUM HYBRIDS DERIVED FROM FESTUCA-ARUNDINACEA VAR GLAUCESCENS AND SELECTION FOR PALATABILITY

This paper reports on the first results of feeding value experiments, assessed with sheep, of hybrids between tetraploid Italian ryegrass (L olium multiflorum, 2n = 4.r = 28) and a progenitor of tall fescue, Fes tuca arundinacea var. glaucescens (2n = 4x = 28). Three hybrid populat ions resulting from either high, low or no selection for palatability were compared with a variety of Italian ryegrass as control and two va rieties of the cultivated hexaploid (2n = 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 th e best palatable tall fescue and to Italian ryegrass. However, selecti on for improved palatability among hybrids did not result in any furth er improvement of other traits, except VI in the hybrid selected for h igh palatability 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. Howeve r, to improve feeding value of hybrids further, similar selection for high palatability appeared questionable and possibly detrimental for o ther agronomic traits because of complicated inheritance in tetraploid L. multiflorum x F. glaucescens hybrids.