Evaluation of Border Leicester × Romney (BR), Poll Dorset × BR, and Suffolk × BR ewes for out‐of‐season lambing

Abstract Three different year groups of Border Leicester × Romney (BR), Poll Dorset × BR (PBR), and Suffolk × BR (SBR) ewes were evaluated for yearling liveweight and greasy fleece weight, and for their 2– and 3–year‐old lambing performance under both June– and August‐lambing policies. Mating of the June‐lambing ewes was induced using progesterone treatment and high ram:ewe ratios. Suffolk × BR hoggets were significantly ( P < 0.01) heavier than PBR and BR ewe hoggets in May, October, and January (at about 16 months of age). Border Leicester × Romney hoggets produced significantly ( P < 0.01) more greasy wool at the yearling shearing than PBR or SBR hoggets. Lambing policy did not influence the proportion of ewes lambing but there were more ( P < 0.05) multiple births in August‐lambing ewes. Birth weights and weaning weights of June‐born lambs were lower ( P < 0.001) than those of their August‐born counterparts. Weight of lamb weaned per ewe joined was 22.1 kg for June‐lambing ewes and 24.3 kg for August‐lambing ewes. June‐lambing ewes produced more wool than August‐lambing ewes but the magnitude of this difference varied between years (0.1–1.1 kg) reflecting a significant ( P < 0.001) policy × year interaction for fleece weight. Differences between the three ewe crosses in the proportion of ewes lambing and the incidence of multiple births were small and non‐significant. Poll Dorset × BR ewes reared the heaviest lambs, whereas lambs from BR ewes were the lightest. Border Leicester × Romney ewes produced more wool (by 0.7–1.2 kg across years and ages) than PBR ewes ( P < 0.001) whereas PBR ewes outperformed the SBR ewes (0.3–0.5 kg, P < 0.01) for wool production. The results of these studies are discussed in the context of the development of out‐of‐season lambing systems and highlight the need for higher prices for out‐of‐season lambs to compensate for the lowered lamb production.