Ewe productive life has a key economic role in sheep production, as longer-lived ewes generally contribute more to lamb outputs over time. In this context, the impact of various factors on the length of Katahdin ewe productive life defined as the time between their first and last lambing was evaluated. Most ewes (around 33%) had only one lambing record and were probably culled before their second lambing, furthermore, among the ewes that had 2 or more lambing events, around 50% were culled before reaching 3 yr of productive life. Ewes themselves born as twins or triplets, and that produced lambs with moderate average birth (approximately 5 kg) and weaning (20 to 25 kg) weights, had longer productive lives. The association between average lamb weights and ewe productive life likely reflects voluntary culling decisions by producers, which may have a positive impact on the annual genetic gain in lamb growth. However, the low number of lambs per ewe lifetime (4.3) is a concern that should be addressed to avoid low selection intensity in females. Moreover, future studies should quantify the involuntary culling rate in ewes to identify whether longevity-related traits should be included in broader breeding objectives.

Read the full article in the Journal of Animal Science.