Energy Value Evaluation And Associative Effects Of Forages For Sheep

A study on energy value evaluation and associative effects of forages for sheep was carrying out in this paper.The nutrient composition and CNCPS nutrient indexes of 13 kinds of forages were measured, furthermore, those forages energy values and the associative effects in forages-based mixtures under different forages and concentrate ratios were evaluated by in vitro and in vivo, and some regression equations by using the nutrient composition and CNCPS nutrient indexes to predict forages energy values, which could be adjusted by their associative effects index(AEI). Finally the comparison of the predicted values and the determined values by in vitro and in vivo was made. The results obtained in the study were as follows:(1) Significantly positive associative effects was observed when each forage mixed with different ratio of same formulated concentrate in the In Vitro trail.Associative effects index(AEI) of 0.080 was the highest when the ratios of concentrate and forages was 3:7, and there was a significant difference(P<0.05) between the five groups, but when the ratio was 4 : 6, the AEI value reduced to 0.040. The AEI values, for different forages, were ranked in following order: silage corn> Russian wildryegrass > Agropyron cristatum > sainfoin> Astragalus absurgens> Alfalfa > Bromus ciliatus, Rape seed stalks > Pea stalks > Soybean stems > Corn stovers > Green naked oat > Wheat straws.(2) The significantly positive correlation was observed between ME and chemical compositions of the forages. So a series optimum regression equations was developed by Multivariate Linear Regression. The results showed that the equation predicting the single forage adjusted by associative effect index was better than that predicting compound feed according to a comparative analysis between the predicted values and determined values. The accuracy of the model is higher and can be used for prediction purpose in practice.(3) The determined values of ME and DE had some difference between in vitro and in vivo values in different forages based mixtures. But the predicted value in vitro was mostly similar to the value determined in vivo for corn silage. Bromus ciliatus occupied in the next. The predicted accuracy for Alfalfa was the poorest one. Those results indicated that it's reliable for using the regression equation to predict the energy values of cereal forages and silages. But there were still some limitation to use for legume forages. Even though The predicted values could be adjusted by correction factors listed in this paper. In the future, it needs some further study for developing the correction factors.