Tropical Grasslands (2003) Volume 37, 4552
Managing rhodes grass (Chloris gayana) cv. Callide to improve diet quality. 2. Effects of stocking rate and irrigation frequency
W.K. EHRLICH1, R.T. COWAN2 and K.F. LOWE1
1 Queensland Department of Primary Industries, Mutdapilly Research Station, and
2 The University of Queensland, Gatton, Queensland, Australia
effects of stocking rate and irrigation frequency on the milk production
of cows grazing nitrogen-fertilised Callide rhodes grass pastures was
studied in south-east Queensland. Pastures were stocked at 3.5, 5.25
and 6.1 cows/ha from January–May inclusive, and irrigated at fortnightly
or monthly intervals.
Yields on offer
pregrazing and pasture, leaf and stem residues after grazing decreased
at the higher stocking rates. Consumption of grass leaf averaged 10.6,
7.7 and 6.5 kg DM/cow/d for cows grazed at 3.5, 5.25 and 6.1 cows/ha,
respectively (P<0.05). Intake of stem averaged 1.3 kg DM/cow/d, with
no difference between treatments (P>0.05). Milk yields averaged 16.6
kg/cow/d for Weeks 7–18 and were unaffected by treatment. Liveweight
loss in the first 15 weeks of the experiment averaged 15, 28 and 43
kg at 3.5, 5.25 and 6.1 cows/ha, respectively (P<0.05). Cows stocked
at 3.5/ha recovered liveweight during the experiment, but liveweight
losses continued for cows at 5.25 and 6.1 cows/ha.
management should aim to harvest a high proportion of leaf, a result
which was achieved under a wide range of stocking rates in this experiment.
Reducing the frequency and total volume of irrigation resulted in reduced
levels of soil water and pasture yield, but did not affect milk production
until the final 3 weeks of the experiment (May).
rate of 3.5 cows/ha allowed cows to maintain body weight and appears
optimal for these pastures.
of the pastures to maintain DM yield with half the applied water input
demonstrates that efficiencies may be gained by closer monitoring of
soil and pasture production in autumn rather than the normal practice
of fortnightly watering. This, combined with the longer grazing interval
of 6 weeks and a stocking rate of 3.5 cows/ha, provided the most efficient
use of the tropical grass pasture resource in late summer and autumn.