Mineral-chemical compounds, digestibility and buffering capacity of Carthamus oxyacantha, Echinops ilicifolius, Silybum marianum, and Eremurus luteus

Khorasan Razavi province has several rangeland species that their nutritive value is still unknown for the animal husbandman. Hence, this experiment was conducted to determine the nutritional potential of some range species containing Carthamus oxyacantha, Echinops ilicifolius, Silybum marianum, and Eremurus luteus (at the flowering stage) with a completely randomized design in 2019. The chemical-mineral compositions, gas production parameters, buffering capacity, and some ruminal fermentation parameters were determined in vitro. The lowest neutral detergent fiber (NDF, 16.41%), acid detergent fiber (ADF, 12.82%), acid detergent lignin (ADL, 5.52%), and crude fiber (CF, 17.63%) contents were obtained in Eremurus luteus (p < 0.0001). The highest crude protein (CP, 19.88%) and ash (21.69%) contents were observed in Silybum marianum (p < 0.0001). Higher calcium (Ca, 30.42 g/kg DM) content was observed in Eremurus luteus (p < 0.0001). The highest contents of nitrogen, potassium, sodium, magnesium, iron, zinc, manganese, and cobalt were related to Silybum marianum (p < 0.0001). Metabolizable energy (ME) ranged from 6.48 for Carthamus oxyacantha to 9.84 MJ/kg DM for Eremurus luteus. Eremurus luteus exhibited the highest (p < 0.0001) dry matter digestibility (DMD, 73.15%) and acid-base buffering capacity (213.05 mEq×10-3). The pH of the plant also ranged from 5.36 for Eremurus luteus to 6.05 for Echinops ilicifolius. The present study showed that each of the four rangeland species can easily meet part of the maintenance requirements of ruminants for nutrients and minerals. According to the measured parameters, Eremurus luteus had the highest nutritive value compared to the other plants.