Improving in sacco incubation technique to evaluate fresh forage for selecting fast-degrading perennial ryegrass (Lolium perenne L.).

摘要

Grasses with fast fibre degradation are required by intensive pasture-based animal production systems to maximize intakes and productivity. To select fast-degrading elite cultivars, a repeatable, rapid and inexpensive screening method should be developed, so large numbers of samples can be evaluated. This study refined the experimental procedure for the in sacco incubation technique using fresh (not dried) perennial ryegrass (Lolium perenne L.). Pre-ruminal incubation treatment and ratio of forage weight to the surface area of the in sacco bag have been tested to evaluate their effects on ryegrass degradation kinetic parameters in the bovine rumen. The timing of sampling and the number of sampling time points were also examined. Results indicated that warming the bags in water prior to incubation led to a faster dry-matter (DM) degradation in the first 12h. If ratio of forage to bag surface area was between 26 and 45 mg DM cm-2, degradation parameters were not affected by bag fill. Sampling between 9 and 12h was critical for determining degradation rate. From these results, an improved in sacco incubation procedure is recommended for screening of ryegrasses used for cultivar selection. The principles demonstrated here for ryegrass may be applicable to other forages, although the critical sampling times for measuring degradation rate are likely to differ.