Digestion kinetics of mature grasses
A.V. CHAVES, G.C. WAGHORN, I.M. BROOKES AND J.L. BURKE
AgResearch, Grasslands Research Centre, Private Bag 11008,
Palmerston North, New Zealand
E-Mail:
Proceedings of the New Zealand Society of Animal Production 2001. 61:
8-12
Digestion kinetics were measured for mature (green and
non-senescent) components of five grass species using in sacco and in
vitro incubations to define rates of degradation and nutrient release.
The data will be incorporated into a dairy nutrition simulation model to
identify limitations in nutrient supply to cows grazing mature pasture
in late spring. Perennial ryegrass, tall fescue, Yorkshire fog, phalaris
and paspalum were hand separated into leaf, stem and inflorescence for
incubations. Percentages of fibre (NDF) in DM fractions ranged from
50-69% (leaf), 63-75% (stem) and 50-68% (inflorescence). Crude protein
concentrations in the DM of the respective fractions were 7.5-23.7%,
3.8-8.3% and 7.9- 12.3%. Soluble DM (% of the total) determined after
mincing accounted for 31-53% of leaf, 26-55% of stem and 20-48% of
inflorescence, and fractional (h -1 ) degradation of the insoluble DM
was very slow, ranging from 0.034-0.113 (leaf), 0.025-0.036 (stem) and
0.033-0.072 (inflorescence). After 24 hours of in vitro incubation plant
nitrogen content become limiting for fermentation in most instances.
Keywords: NZSAPAB;
forages; digestion kinetics; in sacco; in vitro; plant maturity;
dairy cows
Last Updated 7/08/01
