The grazing response of ewe hoggets offered tall
fescue, endophyte-infected (+E) or endophyte-free
(-E) perennial ryegrass all sown with white clover
into a fertile silt loam was examined in April
1990. In a second experiment 2 grazings were
observed where 5 grasses had been overdrilled
into old lucerne growing on stony infertile land.
Pregnaht ewes (August) and ewes with young
lambs (October) grazed 3 replicates of tall fescue,
+E perennial ryegrass, cocksfoot, phalaris and
prairie grass. After the August grazing nitrogen
fertiliser was applied at 0 and 300 kg N/ha to 5 x
2 m subplots in each 30 x 9 m grass plot. April
observations showed that on day one 76% of
grazing time was on tall fescue. During the first 4
days of grazing grass leaf height decreased 60
mm in tall fescue, 43 mm in +E and 42 mm in -E
ryegrass while in the last 5 days decreases were 5,
3 and 25 mm. Over the 9 days’ grazing, pseudostem
height declined 5.2, 1.5 and 5.0 mm, green grass
cover from 62 to 30,65 to 44, and 68 to 33%, and
herbage removal was 940, 1100 and 1300 kg DM/
ha from tall fescue, +E and -E ryegrasses. During
the first 3 days of the August grazing, grass leaf
heights of cocksfoot and +E ryegrass declined at a
much slower rate than in the other 3 species. The
October grazing showed a similar defoliation
pattern on plots without N. Addition of 300 kg N/
ha resulted in very rapid defoliation of all 5 species
during the first day of the 7-day grazing period.
April grazing showed that initially sheep preferred
tall fescue. Even though grazing time was similar
for +E and -E ryegrasses the hoggets consumed
less +E than -E ryegrass, possibly owing to
reluctance to penetrate the +E pseudostem horizon.
The August and October grazings demonstrated
the ability of sheep to discriminate between grass
species and strong rejection of cocksfoot and +E
ryegrass. However, N at a rate similar to a urine
patch produced leaf in all species which was
equally attractive to sheep. The reduced intake of
+E ryegrass measured in the April grazing may
explain some of the lower animal performance of
sheep on +E ryegrass pastures. Equally, grazing preference shown by rate of canopy height decline
in any pasture is probably highly correlated with
pasture intake and animal productivity.[Show full abstract]
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