Associative effects of ensiling mixtures of sweet sorghum and alfalfa on nutritive value, fermentation and methane characteristics

Combining sweet sorghum (SS) with alfalfa (AF) for ensiling has the potential to improvethe nutritive value and fermentation characteristics of resultant silages. However, the opti-mal combination and the associative effects of SS and AF for ensilage have not been studied.Therefore, the aim of this study was to determine the fermentation characteristic and nutri-tive value of silage mixtures with six different SS to AF ratios. The two forages were ensiledin air free silos for 150 days at room temperature as mixtures containing 0:100, 20:80, 40:60,60:40, 80:20, and 100:0 of SS:AF on a fresh weight basis. As the proportion of SS increasedin silage, the content of ash, crude protein, saponins, ammonia, acetic acid, propionic acidand pH decreased, while neutral detergent fiber, acid detergent fiber in organic matter, aciddetergent lignin, water-soluble carbohydrate, starch, total phenolics and condensed tan-nins content increased. The silages were evaluated in 24-h incubations with rumen liquor.The in vitro rumen degradability of dry matter and organic matter as well as gas produc-tion, pH, ammonia, total volatile fatty acids and methane decreased as the proportion of SSincreased in the silage mixtures. This study suggests that high quality silages can be made with SS:AF ratios of 20:80 and 40:60. These silage mixtures offer an opportunity to optimizethe nutrient supply for ruminant production.