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Ewe experience during the perinatal period increases with each litter produced. Thus as ewes age mothering ability should improve consequently having a positive impact on lamb survivability and the performance of their progeny. The effects of ewe age on ewe productivity and the performance of their lambs are presented in Table 1. As ewe age increases to 4 years prolificacy, number of lambs reared per ewe joined and lamb performance, as determined by weaning weight, all increased and lamb mortality declined. The decrease in lamb mortality is probably associated with the greater experience of rearing lambs as ewes age and the higher weight at birth of progeny born to older ewes. Ewes that lambed as 5 year olds had the same lamb output as 4 year old ewes. It is anticipated that ewe prolificacy, or the performance of their lambs, does not decline when ewes lamb at older ages. Consequently, retaining older ewes in the flock (provided there are no reasons to cull e.g. udder problems, mouth issues, poor body condition etc.) reduces replacement rate, and consequently, replacement cost, without any adverse effects on the weight of lamb weaned per ewe.
Table 1. Effect of ewe age on progeny performance