A replicated trial design with ewes continuously stocked on mixed ryegrass/white clover pastures at three target sward surface heights (SSH) of 4, 6 and 8 cm, and 16 ewes per sward treatment (total 96 ewes), was carried out from February through to April 1993. Herbage intake was assessed indirectly from faecal output measured using chromium controlled release capsules and the in vitro digestibility of herbage samples obtained from oesophageal- fistulated sheep run with the ewes. Intake measurements were taken before and after the rams were joined with the ewes. Pasture measurements for the 4, 6 and 8 cm SSH treatments were: SSH, 4.12 vs 6.18 vs 7.97 cm (PSE 0.54 cm, P<0.05); mass, 3358 vs 4291 vs 5231 kg DM/ha (PSE 389 kg DM/ha, P<0.1); dead mater content, 38.9 vs 26.7 vs 40.4% (PSE 5.8%, NS); and organic matter digestibility, 68.0 vs 71.9 vs 63.8% (PSE 1.21%, P<0.0001). Organic Matter (OM) intakes fro the 4, 6 and 8 cm SSH treatments were 1.39 vs 1.86 vs 1.06 kg OM/ewe/day (PSE 0.08 kg OM/ewe/day, P<0.05) for the pre-mating intake and 1.26 vs 1.34 vs. 1.09 kg OM/head/day (PSE 0.06 kg OM/ewe/day, NS) for the mating intake period. Production responses of the ewes for the 4, 6 and 8 cm SSH treatments were: liveweight gain, 72 vs 83 vs. 73 g/day (PSE 5 g/day, NS); and wool growth rate, 1.37 vs 1.44 vs 1.42 mg/cm2/day (PSE 0.03 mg/cm2/day, NS). These results suggest that, in the autumn, maximum herbage intake and ewe performance on ryegrass - white clover pastures can be obtained at a sward height of about 4 cm, and that pasture digestibility and dead matter content in the pastures are the major limiting factors at this time of year.
Proceedings of the New Zealand Society of Animal Production, Volume 54, , 75-78, 1994
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