Short communication: Artificially reared ewes cannot be distinguished from natural reared ewes based on observed maternal behavior or lamb weaning weights

Authors: POSBERGH, CHRISTIAN - Montana State University; Miles, Asha; PETTIFOR, NATASHA - Cornell University; THONNEY, MICHAEL - Cornell University

Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/16/2024
Publication Date: N/A
Citation: N/A

Interpretive Summary: Artificial rearing of lambs is a standard practice used in sheep systems. However, producers sometimes view lambs reared artificially as poor candidates for selection due to not having been maternally raised. This study investigated if artificially reared ewes could be differentiated from naturally reared ewes through maternal behavior observation after birth and historical weaning weight data from the Cornell sheep flock. We found no maternal behavior differences between artificial and naturally reared ewes and a slightly higher weaning weight average for lambs born to artificially reared ewes. This result enables artificially reared ewes to be considered as selection candidates, given no other faults, for producers to increase flock productivity.

Technical Abstract: Artificially rearing lambs is an important aspect of United States sheep production as some flocks select for increased litter size to boost productivity. However, there is a conception among shepherds that artificially reared ewe lambs will ultimately result in poor mothers since they were not naturally raised. The objective of this study was to determine if differences in maternal behavior could be detected between ewes raised artificially and those raised naturally and if dam rearing type had an impact on lamb growth performance. Forty-eight ewes were enrolled comprised of four equal sized groups: artificially reared primiparous, naturally reared primiparous, artificially reared multi-parous, and naturally reared multi-parous. Ewes were observed using remote cameras to record maternal behaviors toward the lambs during and shortly after parturition. Behavior of twenty-nine ewes during the first hour after parturition was analyzed. Independent multivariable regression models were evaluated for: proportion of time spent grooming, proportion of time spent helping the lambs nurse, number of helpful bouts, and the number of negative bouts. No statistically significant difference (p<0.05) was detected between artificially reared and naturally reared ewes for the proportion of time spent grooming and the proportion of time spent helping the lambs nurse. Historical flock data was utilized to evaluate lamb growth between artificially and naturally reared ewes. No detrimental associations between artificially reared ewes and lamb weaning weights were observed. This study shows that artificially reared ewes are no different in terms of mothering behaviors and may be used as potential replacement candidates.