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This study compared ewe and lamb performance in twin-and triplet-bearing/rearing ewes offered varying sward heights from day 64 (P64) of pregnancy until weaning at day 87 (L87) of lactation. Ninety-six twin-and 90 triplet-bearing Romney ewes were randomly assigned on P64 to four replicated sward height treatments (2, 4, 6, and 8 cm sward height). Within 24-36 h of parturition (L1) the ewes were reassigned to two (4 and 8 cm) replicated sward heights until weaning at L87. Ewes grazing the 2 cm sward height during pregnancy were significantly (P < 0.01) lighter at P99 and P132 and at L1 than ewes grazing 4, 6 or 8 cm swards. These ewes also had significantly (P < 0.01) lower dry matter intakes, condition scores, and ultrasonic backfat depths. Litter size had no effect on ewe intake, ewe liveweight or condition score throughout pregnancy and lactation. Ewes grazing the 2 cm sward height had significantly (P < 0.05) lower dry matter intakes during pregnancy than ewes on the 4, 6, and 8 cm treatments. Estimated herbage dry matter intakes measured using n-alkanes were similar to calculated energy requirements. Lambs born to ewes grazing the 2 cm swards during pregnancy were lightest at birth (P < 0.01), but sward height during pregnancy or lactation had no effect on lamb weaning weight or lamb survival rate to weaning. Tripletborn lambs were 0.9 kg lighter (P < 0.05) than twins at birth, with the difference increasing in those lambs reared as a full triplet set to 4.7 kg at L87. Lamb losses were 14% in twin-born lambs and 32% in triplet-born lambs. There was no sward height by litter size interaction for ewe liveweight, intake or lamb birth and weaning weight or survival, therefore the results suggest ewes rearing either twins or triplets should be fed sward height allowances of 4 cm or better during pregnancy. However, there is no need to feed above 4 cm in pregnancy or lactation to optimise lamb weaning weight, lamb survival or ewe liveweight and condition score gain.

Liveweight and condition score of ewes at mating had small positive effects on growth rates to weaning of twin lambs. Shearing mid-pregnancy increased birthweights and weaning weights of twin lambs. To achieve high weaning weights of twin lambs, farmers should ensure ewes attain high liveweights and condition scores at mating and shear mid-pregnancy. It is speculated that the effects of liveweight and condition score of ewes at mating on weaning weights of twin lambs would be greater than those observed in the present study under conditions in which nutrition of the dam is below optimum.

Many farmers are sowing mixed swards containing chicory (Cichorium intybus), plantain (Plantago lanceolata), red clover (Trifolium pratense) and white clover (T. repens) (hereafter termed herb and clover mix). This herb and clover mix has comparable annual dry matter (DM) production to perennial ryegrass white clover pasture (rye/wc), however, it has a different pattern of growth, producing more DM during summer and autumn. The herb and clover mix also has a higher nutritive value and is able to support greater rates of animal production, especially over summer, than rye/ wc in both sheep and cattle. The herb and clover mix is most suited to a rotational grazing interval of 3-4 weeks to an 8 cm residual height, with no winter grazing. When managed appropriately the herb and clover mix is able to persist for at least 2 years and up to 5 years under both sheep and cattle grazing. Keywords: Cichorium intybus, Plantago lanceolata, Trifolium pratense, Trifolium repens, legume, perennial, nutritive value.

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This study compared the effect on foetal growth of shearing ewes in very early pregnancy (day 50) with the effect of shearing later in pregnancy (day 70 or 100). One hundred and sixty ewes were allocated at day 49 of pregnancy to four ‘time of shearing’ treatments — pregnancy day 50 (P50), P70, P100 (no. = 45 ewes per treatment) and unshorn (shearing of this group occurred 43 days after weaning) (no. = 25); two methods of shearing (by standard comb and cover comb); and two levels (1 or 2) of pregnancy/rearing rank. All ewes had been mated over a 28-day period and grazed pasture throughout the trial. The mid point of lambing was 27 August 1996. Live weights of ewes (corrected for fleece weight) were not influenced by shearing time at any stage except at day 45 of lactation when ewes shorn at P50, P70 or P100 were about 3⋅0 kg lighter than unshorn ewes. Shearing method had no effect on ewe live weight. Time of shearing and shearing method had no effect on ewe greasy fleece production or wool tensile strength. Shearing significantly (P < 0⋅05) influenced the birth weight of single- (by 0⋅7 to 0⋅8 kg) but not twin-born lambs. Maternal plasma triiodothyronine concentration increased proportionately by 0⋅47 to 0⋅85 (P < 0⋅05) and lasted for at least 20 days in response to shearing irrespective of time of shearing. No difference in plasma insulin concentration was detected between shearing groups but plasma glucose concentration proportionately increased by 0⋅06 to 0⋅16 (P < 0⋅05) for 10 to 20 days after shearing. These results indicate that shearing between day 50 and 100 of pregnancy can increase lamb birth weights and that the response is associated with an increase in thyroid hormone concentrations in the maternal circulation.

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