A long-term Polypay flock study found higher lifetime lamb totals among ewes that first lambed at one year, alongside a lower rearing ratio.
Records from a long-running flock
A USDA Agricultural Research Service analysis published in July 2026 used 10,094 production records from 2,941 Polypay ewes born between 1995 and 2016. Of these animals, 2,399 first lambed at one year and 542 at two years. The researchers compared the groups' production over their time in the research flock.
Lifetime results differed
Ewes in the one-year group recorded more lambs born and weaned over their lifetimes, greater total lamb weight at 120 days and higher stayability in the flock. Their maternal rearing ratio, measured as lambs weaned relative to lambs born, was lower. The results describe associations in this research flock rather than a controlled change in breeding age.