Effects of pre-lamb shearing on feed intake and associated productivity of May- and August-lambing ewes

The effects of pre-lamb shearing on feed intake and wool/lamb production of May (autumn)- and August (spring)-lambing ewes were examined. Mixed age Border Leicester x Romney ewes mated to lamb in May or August (60 ewes/ lambing policy) were divided at random into two groups (balanced for pregnancy status and liveweight). One group was shorn on Day 118 of pregnancy (P118) and the second group left unshorn. Measurement of pasture intake was carried out over three periods before lambing (P113-117, P119-130, and P141-144) and three periods after lambing (L (lactation day) 8-11, L21-25, and L29-33) using intraruminal chromic oxide controlled release capsules. Intake of ewes was not affected by shearing treatment during pregnancy or lactation except during P141-144 when organic matter intake was significantly greater for shorn ewes than for unshorn ewes (1739 ±58 versus 1526 ± 59 g/day, P < 0.05). Ewe liveweights and condition scores were similar for both shearing treatments during pregnancy and lactation. Over the period P118-LI3, pre-lamb shorn May-lambing ewes had significantly (P < 0.01) higher clean wool growth rates than comparable unshorn ewes (0.927 ± 0.042 versus 0.721 ± 0.048 mg/cm 2 per day), but this effect was not found in the August-lambing group (0.542 ± 0.041 versus 0.641 ± 0.045 mg/cm 2 per day, P > 0.10). Clean wool growth rate was greater in shorn ewes than in unshorn ewes (additive with effects of lambing policy) over L13-84 (0.896 ± 0.024 versus 0.801 ± 0.025 mg/cm 2 per day, P < 0.10). Lamb liveweights at birth and at three subsequent measurement times to weaning were not affected by dam's shearing treatment. In general, feed intake and productivity responses to pre-lamb shearing were similar in both lambing policies, except for wool growth rates which were influenced by shearing to a greater extent in May-than in August-lambing ewes. Pre-lamb shearing is likely to be a viable option for autumn-lambing policies and appears to have a more marked positive effect on wool growth of autumn-lambing ewes than that of spring-lambing ewes.