Dalagh: An Iranian half-tailed sheep breed with continuous annual ovarian activity at a mid-latitude temperate region

摘要: At mid and high latitudes, seasonal breeding is prevalent in sheep production which makes ewes to reproduce for a restricted window of time. Unconfirmed local reports have declared continuous reproductive activity half-tailed breed, Dalagh, at midlatitude region (371N) Golestan province, northern Iran. The present study aimed evaluate the ovarian thyroidal Dalagh during one-year-long trial. Fifty-five fertile healthy were isolated from rams bled weekly quantify serum levels progesterone (P4), tri-iodothyronine (T3), tetra-iodothyronine (T4), using radioimmunoassay. day-length ambient temperature recorded daily. lowest overall mean P4 level was winter; whereas, no differences found among those other seasons. values T3 comparable spring, autumn, winter, being higher than that summer. highest value T4 winter ones observed spring summer with autumn lying between these extremes. variation showed decreasing trend towards end trial, where late May September one noted March. Interestingly, individual records each ewe revealed none animals studied an 8-week or longer period wherein fell below 1 ng/mL, threshold reported anestrous status. Although had steady trend, increasing as trial proceeded, January July, respectively. Correlation coefficients ,T 3, þ0.21, –0.25, –0.42, corresponding þ0.30, –0.57, –0.84 T4, Data suggested despite reproducing temperate region, cyclicity throughout year would be beneficial exploit it schemes decrease seasonality possibly latitudes. Future studies may interested searching underlying mechanism(s) involved.