Formulating total mixed rations from forages - defining the
digestion kinetics of contrasting species
J.L. Burke, G.C.Waghorn, I.M. Brookes, G.T. Attwood and E.S. Kolver
AgResearch, Grasslands Research Centre, Private Bag 11008,
Palmerston North, New Zealand
Proceedings of the New Zealand Society of Animal Production.
2000 60: 9-14
The work described here is the first step in formulating
forage-based TMR rations for dairy cows, based on digestion kinetics
derived from in vitro and in sacco incubations. Kinetic
information has been obtained from 23 contrasting fresh and conserved
forages species, including temperate and tropical grass species, legumes
(including Lotus spp. containing condensed tannins), herbs, silages,
lucerne hay and maize grain. All forages were minced to a particle size
similar to chewed material. Estimates of DM solubility (% DM) and
fractional dry matter degradation rates (h-1) determined by
in sacco incubations include: white clover (39%, 0.195),
perennial ryegrass (45%, 0.114), tall fescue (46.8%, 0.051), paspalum
(27%, 0.068), sulla (51.4%, 0.121), chicory (41.8%, 0.260), pasture
silage (41%, 0.083), maize silage (28%, 0.042). In vitro
incubations resulted in five-fold differences between forages in net
ammonia release, 2-3 fold differences in volatile fatty acid yield and a
three-fold difference in acetate:propionate ratio. The data will be used
in simulation models to identify optimal forage mixtures for meeting the
nutritional needs of high-producing dairy cows.
Keywords: NZSAPAB;
in sacco; in vitro; forages; digestion kinetics;
dairy cows.
Last Updated 12-07-2000
