Studies on the breeding season of Icelandic ewes and ewe lambs

• Published in: The Journal of Agricultural Science
• Main Author: Dýrmundsson, Ø. R.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Cambridge University Press (CUP) 1978
• Subjects: Iceland
• Online Access: http://dx.doi.org/10.1017/s0021859600055350; https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0021859600055350

Summary The paper reports on a study, conducted in four successive seasons, of sexual development and breeding activity in females of the Iceland breed, the only breed of sheep kept in the country. The ewe lambs normally attained puberty in their first year of life, on average at 7 months of age, with marked individual variation in both age and body weight at first oestrus. Ewe lambs always showed oestrus on average slightly later than mature ewes (2–9 years), the mean date of onset of the breeding season of the latter being 8 December, however, with considerable individual variation. Furthermore, ewe lambs had a shorter breeding season (1–4 months) than ewes (4–6 months) and they appeared to experience more silent heats resulting in less regular cyclic activity. There seemed to be a minor increase in the duration of the oestrous cycle with age and ewe lambs clearly exhibited shorter oestrus (heat) than ewes. With seasonal breeding activity ranging from November to May the mid-breeding season occurs some 4–7 weeks after the shortest day.