Evaluation of nutritional properties of alfalfa and sainfoin forages by gas production techniques

Two forage species alfalfa (Medicago sativa), and sainfoin (Onobrychis viciifolia Scop.), at two consecutive growing season (spring and summer), were studied for their chemical composition and in vitro gas production characteristics. Data on cumulative gas production (mL gas/g DM) were fitted to the non-sigmoidal model, and for evaluation of model, the concordance correlation coefficient (CCC) was used to assess the agreement between predicted and observed data. Chemical analysis showed that nutrient composition was affected by the forage type. Concentration of fiber components (NDF, ADF, cellulose and crude fiber) were higher in alfalfa compared to sainfoin (P < 0.05). Concentration of fiber components was higher in the first cut compared to the second cut (P < 0.05) in both forages, but cellulose content was not affected by the growing season (P > 0.05). The results showed that there is a great potential for improving the analytical capacity of the technique, by reducing the length of incubation from 48 to 24 h for studies on high quality forages. This study showed that 24 h incubation provided informative results with high reproducibility of the measurements, clear relationship and high correlations between different parameters and the relative feed value (RFV), and also reliable models for prediction of metabolizable energy with high values for the coefficients of determination. The results indicated that the logistic model can be used to describe the in vitro gas production kinetics (CCC = 0.992). It was concluded that, in addition to chemical analysis, the in vitro gas production is a useful and simple technique for determination of the relative feeding value of these forage species.