Effects of animal age and different months of grazing season on grazing behaviour and diet selection of Zandi ewes grazing in steppe rangelands (case study: Yekke bagh, Qom)

As animals graze selectively, prediction of their nutrient intake and intensity of the impact on rangelands vegetation needs an understanding of the animals’ foraging decisions. Therefore, a study area was selected in steppe rangelands in Qom province and one enclosure (1ha. area) was contracted in which forage plants production and intake were measured during grazing period. The feeding behaviour of 3 Zandi ewes (1, 3 and 5 years old) in free grazing system was evaluated considering the plant palatability and preference value based on close observation method in each month of grazing season. Then diet composition and preference index for each plant species were calculated and compared. Grazing cycle, distance and motivation speed and time spent for grazing / resting or walking were assessed using GPS equipment mounted on the back of the sheep. The results showed that during grazing season Buffunia macrocarpa and Annuals (grasses and forbs) had the highest preference index and diet composition. Diet selection and time spent on forage plants varied slightly among three ewe ages (p<0.01). There was no correlation between two evaluation methods of preference (paired plots and close observation). Considering the plants phenology and soil moisture conditions, middle Farvardin (April) for entrance and late Aban (November) for exit of livestock were proposed. The highest percentage of grazing time occurred in Farvardin and the lowest one was in Tir(June). Because of low species diversity, in arid rangelands, livestock diet selection will be restricted. Animal experience, plant’s flavor, plant cover and composition were the most effective factors on sheep preference. Due to high diversity and grazing on shrubs, grasses and forbs, Zandi sheep could be classified as Intermediate feeders, in Yekke bagh rangeland.