Effects Of Different Areas And Seasons On The Quality Of The Native Forage Grass From High-cold Steppes

This 4×2 factor experimental study was to evaluate the effects of different areas and seasons on the quality of the native forage grass in high-cold steppes. Eight kinds of native forage grass in high-cold steppes form four areas (winter-spring and summer-autumn grassland in Luqu and Hezuo region) and two seasons (cold-season and warm-season) in Gannan were selected to measure the nutritional components, evaluate the rumen degradation characteristic by the Cornell Net Carbohydrate and Protein System (CNCPS). Results indicated that:(1) General nutrients:Areas had significant effects on the contenhts of dry matter (DM), ether extract (EE), crude protein (CP), crude ash (Ash), nitrogen free extract (NFE) and organic matter (OM) of native forage grass in high-cold steppes (P<0.05). Irrespective of areas, the contents of free water, DM, EE, CF and OM had marked difference between warm-season forage grass and cold-season forage grass (P<0.05). Moreover, there was a significant interaction effect on the contents of EE, Ash, NFE, OM, CP and crude fibre (CF) of native forage grass in high-cold steppes between areas and seasons (P<0.05). Among them, the contents of Ash of the forage grass from Hezuo summer-autumn gasssland (HZX) and the forage grass from Hezuo winter-spring gasssland (HZD) were markably higher than that of the forage grass from Luqu summer-autumn gasssland (LQX) and the forage grass from Luqu winter-spring gasssland (LQD) (P<0.05), and the contents of OM of LQD and HZD were higher than that of LQX and HZX significantly (P<0.05), and yet, the contents of Ash were lower significantly lower than that of LQX and HZX (P<0.05). At the exclusion of areas effects, the contents of free water, CP and EE of warm-season forage grass significantly higher than which of cold-season forage grass (P<0.05), yet the contents of CF were lower than that of cold-season forage grass (P<0.05), moreover, the contents of Ash had a trend to rise when cold-season. In addition, considering the general nutrients, the quality of the warm-season forage grass from Luqu winter-spring gasssland (LQD-N) were the best, while which of the cold-season forage grass from Hezuo summer-autumn gasssland (HZX-L) were the worst.(2) Carbohydrates:The contents of total carbohydrates (CHO), neutral detergent fiber (NDF), acid detergent lignin (ADL) and the nonstructural carbohydrates accounted for the proportion of the total carbohydrates [NSC (%CHO)] were significantly different in all areas (P<0.05). Compared with HZD and HZX, the contents of CHO, Starch, hemicellulose (HC), and NSC (%CHO) of LQD and LQX were higher (P<0.05), while the contents of NDF, ADF and ADL were lower (P<0.05). On the other hand, the contents of CHO, NDF, ADF, ADL and cellulose (C) of cold-season forage grass in high-cold steppes were higher remarkably than that of warm-season forage grass in high-cold steppes (P<0.05), while the value of NSC (% CHO) were lower significantly than which of warm-season forage grass (P<0.05). Then, the interaction effects between different areas and seasons on the contents of CHO, Starch, ADF, ADL, HC, C and the value of NSC (%CHO) of native forage grass in high-cold steppes met the significant level (P<0.05).(3) Proteins:Areas had significant effects on the contents of acid detergent insoluble protein (ADIP) and neutral detergent insoluble protein (NDIP) (P<0.05). The contents of NDIP, ADIP, non-protein nitrogen (NPN) and soluble crude protein (SOLP) of HZD and HZX were higher than that LQD and LQX (P<0.05), meanwhile, the contents of ADIP of LQD and HZD were lower than that of LQX and HZX (P<0.05). Regardless of areas, the contents of NDIP, ADIP, NPN and SLOP of native forage grass in high-cold steppes had marked difference between warm-season forage grass and cold-season forage grass (P<0.05). The contents of NDIP, NPN and SOLP of forage grass in warm-season were higher than that in cold-season (P<0.05) while the contents of ADIP and CHO significantly decreased (P<0.05). In addition, areas and seasons had interaction effects on the contents of NDIP, ADIP and NPN of forage grass (P<0.05).(4) Minerals:The contents of macroelement (Ca, Mg, Na and K etc.) and microelement (Fe, Cu and Mn etc.) and the ratio Ca to TP had significant differences in all areas (P<0.05); futhermore, the contents of Fe, Cu and Mn of LQD were low but the contents of Cu and Mn of HZX were high. (P<0.05). The contents of Ca, Mg, Na of HZD and HZX were higher than that of LQD and LQX (P<0.05). Regardless of areas, the contents of TP,Mg, K and Zn in warm-season forage grass were significant higher than that in cold-season forage grass (P<0.05) while the contents of Na, Fe, Mn and the ratio Ca to TP markedly decreased (P<0.05). In addition, areas and seasons had significant interaction effects on the contents of TP, Na, K, Cu, Mn and the ratio of Ca to TP of forage grass from high-cold steppes (P<0.05).(5) Degradation characteristic:In this study, the contents of repid degradation fractions of carbohydrate (CA), low speed degradation fractions of carbohydrate (CB2), nondegradable fractions of carbohydrate (CC), repid degradation fractions of non-protein nitrogen protein (PA), repid degradation fractions of true protein (PB1), medium speed degradation fractions of true protein (PB2), and nondegradable fractions of protein (PC) of native forage grass were significantly differet in all areas (P<0.05), furthermore, LQD-N had the highest contents of CA and CB2 (P<0.05) while had the lowest contents of CC and PC (P<0.05). Regardless of areas, season had marked effects on the contents of CA, CC, PA, PB1, low speed degradation fractions of true protein (PB3) and PC of native forage grass (P<0.05), furthermore, the contents of CA, PA and PB3 in warm-season forage grass were markedly higher than that in cold-season forage grass (P<0.05), however, the contents of CC, PB1 and PC of native forage grass decreased significantly in warm-season (P<0.05). In addition, areas and seasons had significant interaction effects on the contents of CA, medium speed degradation fractions of carbohydrate (CB1), CB2, CC, PB1, PB2 and PC (P<0.05).In summary, it indicated that areas and seasons had different degree of influences on the nutrients, minerals, and the degradation characteristic of native forage grass in high-cold steppes. Generally, the nutritional value of forage grass in warm-season was better than that in cold-season, the LQD-N region was the best, and the HZX-L region was the worst.