Utilizing a multi-index decision analysis method to overall assess forage yield and quality of C3 grasses in the western Canadian prairies

Seasonal dynamic of forage quality and yield has a major impact on livestock production. A sound evaluation on quality and quantity of forage is useful for cost-effective utilization of forage. However, forage quality and yield can vary with forage species, harvest seasons and yearly climate conditions. To improve forage use efficiency, a field experiment (2008-2010) was conducted in Swift Current, Saskatchewan, Canada. Dry matter yield and quality indicators (fiber, protein, digestibility and minerals) were measured for nine cool-season grasses harvested in June, August and October. The interrelationships and attributes among quality indicators were determined by principal component analysis (PCA) and the weights of quality indicators were calculated by entropy weight (EW) method. To synthesize different attribute indicators into a comprehensive index that reflects quality ranking of different forage species, an integrated multi-index decision analysis method, i.e., PCA-based TOPSIS with EW, was used in this paper. The evaluation process and results showed that the interrelation patterns and positive or negative attributes for quality indicators were consistent with years and harvest seasons, whereas the rankings of most grasses in yield and comprehensive quality varied with years and harvest seasons. According to the yearly and seasonal rankings of forage quality and yield, flexible production tactics and adaptive management techniques should be considered within the western Canadian prairie region. For instance, Northern wheatgrass (Agropyron dasystachyum) can be recommended to be mixed with high quality forages due to its high yield in any harvest season. Meadow bromegrass (Bromus Riparius) can be recommended to be mixed with high yield forages due to its high quality in summer and fall. These findings will provide valuable information for forage breeders, and livestock and forage managers to maximize grass utilization efficiency while balancing yield and quality.