Gestation length and some factors affecting in Iranian Arab mares of Tabriz

The length of gestation in 11 Persian Arab mares inTabriz horse stables was distinguished in 23 full-termdeliveries over the 5-year period 1380-1384. The mean gestation length was 331.43 ± 13.6 (SD) days, (307-361 days). There was no significant sex difference amongpregnancies. Season and month of birth had significanteffect on gestation length. Longer gestation period was seen with increasing age mare. Number of parturition had no effect on gestation length. Significant linger gestation period was seen in spring compare to summer and there was significant longer period (15 day) between second and first month of spring (p