Characterization of the productive performance of Highlander sheep in Southern Chile. I. Female reproductive traits

• We characterize seasonality, follicular dynamics and ovulation and the reproductive performance exhibited by the Highlander breed.
• Based on progesterone profiles Highlander ewes have longer breeding season than Suffolk ewes.
• Highlander ewes have an average interovulatory interval characterized mainly by 3-follicular waves that ended in double ovulations.
• Reproductive performance at commercial farms met the requirements for prolificacy under easy-care systems.

The present study aimed to characterize seasonality, follicular dynamics and ovulation and the reproductive performance exhibited by the Highlander breed. In the first part of the study, 32 ewes were allocated to two experiments: in the first one, 8 Highlander and 8 Suffolk ewes used as reference were subjected to serial blood sampling to characterize seasonality by progesterone profiles measured by RIA; in the second experiment, 16 Highlander ewes were used to characterize the follicular dynamics and ovulation during an interovulatory cycle by systematic transrectal ultrasonography. In the second part of the study, lambing records of 4740 Highlander ewes from 3 commercial farms were used to characterize the reproductive performance of the breed during 3 breeding seasons. Results showed that in our latitude the breeding season of Highlander ewes starts by the end of January and finished by the end of August, 15 days earlier and 15 days later than Suffolk ewes, respectively. The average features of the interovulatory cycle were as follows: the cycle lasted 16.8 days, luteolysis took place at day 13.4 of the cycle and it took another 3.9 days to ovulate; 16/16 ewes ovulated 1.88 follicles of 5.9 mm in diameter that led to corpora lutea (CL) of 10.9 mm in diameter. Ewes exhibited mainly (>70%) 3 follicular waves during the cycle, with a cohort of 3.3 follicles ≥3.5 mm in diameter emerging at days 1.7, 7.2 and 11.9 of the cycle; follicular waves lasted 6.7 days with a growth phase of 4.4 days during which large follicles grew at a rate of 0.67 mm/day. About 50% of ovulated follicles in double-ovulating ewes emerged in the precedent follicular wave. When the reproductive performance was assessed in commercial flocks, 82.3%, 95.6%, 182%, and 174% was obtained for conception, fertility, fecundity and lambing rates respectively with no differences between flocks and seasons; a lamb frequency of 22.8%, 59.2%, 17.5% and 0.56% for 1, 2, 3 and 4 lambs was registered at lambing.