Diet composition, herbage intake and digestibility in Inner Mongolian Cashmere goats grazing on native Leymus chinensis plant communities

The botanical composition, intake and digestibility of the diet selected by Inner Mongolian Cashmere goats grazing on a native Leymus chinensis plant community were measured in two grazing periods (June and August) using the n-alkane markers. In each grazing period, 48 Inner Mongolian Cashmere goats (24 wethers and 24 does with an average live weight of 22.1 ± 1.2 kg and 19.6 ± 0.8 kg, respectively) were divided in two groups (G1: grazing group; G2: cage-fed group) of 24 animals each. Based on the observation of G1 grazing behaviour, G2 goats were fed on herbage obtained by a simulative method and were housed in metabolism cages to determine the alkane faecal recoveries. Diet composition was estimated by comparing the odd-chain n-alkane pattern (C₂₅–C₃₅) of the selected plant species with the n-alkane faecal concentrations, corrected for their incomplete faecal recovery. The alkane pair C₃₂:C₃₃ and C₃₆ alkane were used to estimate intake and diet digestibility, respectively. The results showed that the increase of herbage availability from June to August, resulted in higher (P < 0.05) DM, CP, ME, ADF and NDF intake of both wethers and does, with no evident changes in ADF and NDF intake in does., The intake of nutrients differed significantly between wethers and does in both experimental periods, except for NDF in EP1 and ME in EP2. Differences between grazing seasons and goats' sex in nutrients digestibility were not observed. Diet composition indicated seasonal differences, being Sonchus brachyotus, Artemisia frigida and Phragmites communis the main components of the diet in June. However, Suaeda corniculata, Chloris virgata, Xanthium sibiricum and Echinochloa crusgalli became the main diet components in August. Moreover, the sex affected significantly the diet choices in both grazing periods.