Author:
Young J.,Doyle P. T.,Booth P.
Abstract
We compared strip grazing (SG) as a means of controlling wool growth rate,
reducing variation in fibre diameter along the staple, and of carrying more
Merino sheep through winter on green annual pastures, with set stocking (SS)
in 3 experiments. In experiments 1 and 2, SG involved grazing to a residual
feed on offer (FOO) of 400 kg DM/ha with an estimated intake of about 0.8
kg DM/day for each sheep. Treatments commenced after pasture establishment
in autumn–winter, with both treatments stocked at 20 wethers/ha
until late spring. During spring, average liveweight changes were lower
(P<0.01) under SG than SS (55
v. 153 g/day experiment 1; –16
v. 217 g/day experiment 2). Strip grazing, compared
with SS, reduced (P<0.01) the variation in wool
growth rate and fibre diameter along the staple leading to lower
(P<0.01) clean wool weights (3.54
v. 3.94 and 2.97 v. 4.12 kg), but
finer (P<0.01) (20.9 v. 22.0
and 19.5 v. 21.5 mm), stronger
(P<0.01) (28.6 v. 25.3 and 39.9
v. 35.5 N/ktex) wool. However, there was also an
increase in vegetable matter content of the wool. The effects on annual
pastures were to increase grass (79 v. 48 and 59
v. 25%) and reduce legume (12
v. 36 and 22 v. 54%)
content at the end of spring.
In experiment 3, two strip grazing treatments were used: SGl with a residual
FOO of about 400 kg DM/ha and a stocking rate of 28 wethers/ha; and
SGh with a residual FOO of about 800 kg DM/ha and stocking rate of 14
wethers/ha. The stocking rate for SS was 12 wethers/ha. SGl, following
an autumn deferment, enabled a stocking rate of 28 wethers/ha to be
sustained through winter without supplementary feeding. This is substantially
higher than the district average stocking rate of about 7 sheep/ha. Strip
grazing reduced (P<0.01) liveweights at the
completion of treatments (SGl 41.9 v. SGh 47.9
v. SS 60.3 kg), reduced
(P<0.01) clean wool weights (3.40
v. 3.72 v. 4.54 kg) and mean fibre
diameter (19.1 v. 19.0 v. 20.9 m),
but increased staple strength (21.3 v. 19.0
v. 16.9 N/ktex).
These results are discussed in relation to opportunities to utilise strip
grazing in sheep production systems on annual pastures in south-western
Australia.
Subject
General Agricultural and Biological Sciences
Cited by
6 articles.
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