Genotypic variation in in sacco dry matter degradation kinetics in perennial ryegrass (Lolium perenne L.)

Fast degrading perennial ryegrass (Lolium perenne L.) is a desirable characteristic to select for because it can result in increased feed intake by grazing ruminants. Sufficient range in genotypic variation of dry matter (DM) degradation kinetics is a prerequisite for selection. To investigate the genotypic variation, 77 perennial ryegrass accessions sourced internationally, grown in autumn in the same conditions and harvested in the vegetative state, were examined using an in sacco technique. From the time course of DM disappearance, soluble fraction 'A', potentially degradable fraction 'B', indigestible fraction 'C' and the degradation rate k of fraction 'B' were estimated. The results indicated that a large range in genotypic variation was present in all degradation parameters. Fraction 'A' ranged from 0.48 to 0.60, with the highest five accessions being 21% higher than the lowest five. Degradation rate k of fraction 'B' ranged from 0.069 to 0.199/h, with the fastest five being 125% higher than the slowest five. There were no strong correlations between degradation parameters and chemical composition. In conclusion, there was considerable genotypic variation in DM degradation kinetics among perennial ryegrass accessions and this presents plant breeders with ample opportunity to select for fast degrading perennial ryegrasses.