Document Type : Research Paper
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Abstract
In this study, samples were collected in several phenological stages (in two growing seasons of 2010 and 2011) to assess the effects of two grazing systems (continuous and short-term) on forage quality of three key range species of Bromus tomentellus, Cephalaria kotschyi and Ferula haussknechtii in Zardawan ranch, and two species of Bromus tomentellus and Ferula haussknechtii in Baharestan ranch. The grazing systems are short-term and continuous in Zardawan and Baharestan, respectively. The studied traits were dry matter digestibility (DMD), acid detergent fibers (ADF), water-soluble carbohydrates (WSC), ash and crude protein (CP). Near infra-red spectroscopy (NIRS) was used to measure these traits. A combined analysis based on unbalanced completely randomized design was conducted for statistical analysis. Mean comparisons were made by Duncan's multiple range test. Results indicated that for all species, phenological stages affected all studied traits, without any exception, so that the late vegetative growth stage could be recommended as a proper time for livestock entry to the rangeland. In the face of variation sources studied, different species showed different responses. The comparison of species habitats showed that none of forage quality traits of B. tomentellus and F. haussknechtii differed in the two sites studied. The mean of most forage quality traits were similar in the two years. According to the results, short-duration grazing system of the Shagaldari did not affect the measured traits negatively, but continuous heavy grazing caused to decreased forage quality.
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