Determination of diet selection of livestock with direct observation technique, bite-count and time recording in arid rangelands(Case study: Nodoshan rangelands of Yazd province)

Arid and semi-arid rangelands cover a large part of Iran. Identifying of diet selection by livestock is very important for grazing management of arid rangelands. To determine diet of sheep and goats in the arid rangelands of Yazd, direct observation technique (bite-count and time recording) were employed in a mixed herd of local herders. A least 6 animals (sheep and goat) were marked and chased from distance of 50 to 80 cm for the period of 15 minutes. The number of bits taken and time spent for the important range spent forms (grasses, forbs, and shrubs) were recorded for early, mid-, and late grazing periods. Factorial experiment of randomized complete design was used to compare different growth forms for each kind of animal in the three grazing periods using the counted bits and time recording. Diet variation were similar for sheep and goat (p<0.05). In general, the highest percent of bite-count and time recorded were related to brushes and there wan no any changes in diet selection during the grazing periods. Brush’s preference index was more than one but this index for grasses and forbs were less than one. These results show that the brushes have higher palatability. Similarity Index of diet selection by sheep and goat were more than 76%. Therefore, diet selection by sheep and goat are similar in this rangelands. Also, variation of counted bits and time recording were similar and Similarity Index by bite-count and time recording were more than 75%. However bite-count method is estimated by a limited tools and resources, therefore, it has preference to time recording methods.