Nutritive evaluation of common cultivated forage crop for dairy cattle in Heilongjiang Province

The study was conducted to determine chemical composition and 72 hours dry matter degradability of 14 variety of common cultivated grass by nylon bag method with objective of evaluating nutritional value of grass for dairy cattle.The results showed: in terms of chemical composition and ruminal dry matter degradability(RDMD),rampant wild-soybean(Glycine max L.) and wild soybean had highest nutritional value of all legume grass,and almighty alfalfa(Medicago sativa L.),No.2 grassland alfalfa,sickle alfalfa(Medicago falcata L.) and Pangduo alfalfa were second to wild soybean,erect milkvetch(Astragalus adsurgens),No.2 Tumu alfalfa,No.1 grassland alfalfa were medium.Large-leaf alfalfa,yellow sweetclover(Melilotus officinalis L.) and teke alfalfa were the lowest.There was significantly positive correlation between RDMD and CP content in legumes(P0.001).Ruminal dry matter degradability(RDMD) of legume hay can be predicted content by the regression equation in which CP content was an independent variable.Grading index of various legume forages were estimated by using DMI and NE prediction model.The present research classed these forages into five categories according to GI value as follows.wild soybean was excellent grade,almighty alfalfa was very good grade,No.2 grassland alfalfa was good grade,rampant wild-soybean,No.1 grassland alfalfa,Pangdu alfalfa,Japanese alfalfa,No.2 tumu alfalfa,erect sickle alfalfa and erect milkvetch were fair grade,teke alfalfa,large-leaf alfalfa and yellow sweetclover were poor grade.It is impossible to precisely evaluate nutritional value of forage using single index(for example,chemical composition,dry matter degradability).As long as DMI,nutrient content,digestibility and available energy were together taken into account,evaluation of forage with precision is possible.Differentiation of a variety of forage with minor nutrient discrepancy by using GI can indicate that GI is an authoritative index evaluating forage quality.