چكيده لاتين :
Measuring the preferred value of rangeland plants is one of the most important factors in
determining rangelands' grazing capacity. The preferential value of rangeland plants is measured based on the
type of livestock which uses the rangeland and the changes made in the rangeland during the grazing season.
This study sought to investigate the palatability of rangeland plant species within the Sirik rangeland
(Hormozgan province) during the grazing season (January to May) of the years 2007-2010.
Materials and Methods: The study area was located at sand dunes of Sirik city (Hormozgan province) at 26˚
39ʹ 12ʺ and 57˚ 4ʹ 26ʺ overlooking the sea. The 30-year ambrothermic curve of the study area showed that the
wet and dry seasons lasted one and eleven months, respectively. The average minimum and maximum
temperatures of the study area in the coldest and warmest months of the year were found to be 14.36 °C and
33.78 °C, respectively. However, the lowest and highest temperatures in the region were 5.5 and 48.5 °C,
respectively, and its average 30-year rainfall rate was 121.8 mm.
The region's rangeland type was a mixture of Sphaerocoma aucheri and Cenchrus pennisetoformis. In the
study area, seventy plant species from twenty-eight genera were collected and identified, the most important of
which were Moltkiopsis Ciliata, Heliotropium bacciferum, Cyperus conglomeratus, and Panicum turgidum. The
livestock examined in this study was Tali goat that is bred in Hormozgan, Sistan and Baluchestan, and Bushehr
provinces.
This study was conducted in Sirik rangeland, Hormozgan province, throughout the grazing season (January to
May) for four consecutive years (2007 to 2010). The study area comprised a one-hectare enclosed area located
on sand dunes ten kilometers away from Sirik city, overlooking the sea. At the beginning of the grazing season,
five similar rootstocks were selected for each species and marked inside and outside the enclosed area.
The forage of each rootstock was placed in a separate bag and weighed. Then the consumption percentage
was determined for each species. Each species' share in the livestock diet was determined throughout the grazing
season by calculating the percentage of production and consumption of species inside and outside the enclosed
area. Moreover, the preference index was obtained by dividing the species' share outside the enclosed area by its
share inside the area. Finally, preferential value indices were determined according to the classification proposed
by Rosiere et al. (1975). The study's results were analyzed in a time-based split-plot statistical design through a
complete randomized block design in SAS software, followed by comparing the statistical mean of the studied
features with the results of the LSD test.
Results: The analysis of the variance of the preferred index showed that there was no significant difference
among the studied years. However, a significant difference was found between the months of the study period and between the species examined. The years of the study period were grouped together in one statistical
category, and the months of the study period were classified into two statistical categories. The highest value of
the preference index was found in March, which was in the same group as January. Cenchrus pennisetoformis
showed the highest preference index with the value of 1.516, followed by Cyperus conglumeratus, whose value
was reported to be 1.338, both of which were not statistically significant. It was also found that Cenchrus
pennisetoformis was a relatively palatable species (relative preference), Cyperus conglumeratus, Sphaerocoma
aucheri, Moltkiopsis Ciliata, and Panicum turgidum were moderately palatable species (moderate preference),
and Heliotropium bacciferum was identified as almost a non-palatable (relative avoidance) species.
Discussion and Conclusion: Cenchrus pennisetoformis was identified as the highest livestock preference in
Sirik rangeland, Hormozgan province. According to the classification table proposed by Rosiere et al. (1975),
the species is classified as palatable with a preference index of 1.516. Moreover, Cenchrus pennisetoformis was
one of the region's low-density and highly consumed species. The second livestock preference in Sirik rangeland
was Cyperus conglumeratus, whose preference index was found to be 1.338, representing a boundary between
the ratio of good food and average good food. The two species were then grouped together in a statistical
category. The third preference rank belonged to Sphaerocoma aucheri with a value of 0.960, which was a highly
distributed and consumed species in the region with the highest dense value. It should be noted that this species
plays an essential role in Tali goat's nutrition at the end of the grazing season, i.e., April and May, when the
annuals are dried up.
Other preference indices belonged to Moltkiopsis ciliate and Panicum turgidum, with index values of 0.819
and 0.800, respectively, both of which are classified as moderately palatable species. Moreover, annuals with a
preference index of 0.729, including Stipa capensis, Plantago psylium, Erucaria hispanica, Mathiola
longipetala, Fagonia bruguieri, Anagalis arvensis, and Medicago polymorpha were among the moderately
palatable species. However, it should be noted that at the beginning of the grazing season, the livestock tends to
graze those plants that are more than one year old, while at the end of the grazing season, when the grasses are
dried up or sowed, the one-year-old plants are less favored by the livestock. Finally, the last preference index
belonged to Heliotropium bacciferum with an index of 0.605, which was classified as an almost non-edible
species.
