Study on dominant pasture grasses in different types of natural grasslands and their combination effects with supplemental maize

<p indent="0mm">With the intensification of conflicts between the yield of natural grassland forage and the demand for feed by livestock intensifying, the degradation of grasslands has led to a decrease in the quality of forage provided. Therefore, supplementing corn for grazing livestock has become common. Improving the utilization rate of forage is beneficial for maintaining the balance between grass and livestock. Therefore, it is particularly important to clarify the types and nutritional values of dominant forage and supplementary feed in grasslands, as well as their digestion and interaction in animal bodies. <italic>In vitro</italic> fermentation technology is widely used in the evaluation of forage nutritional value and the study of feed combination effects due to its simple, rapid, and economical methods. This technology effectively overcomes the complexities of animal trials and the variability influenced by individual animal differences and physiological conditions. The aim of this study is to investigate the nutritional value of main forage grasses in different types of grassland and their interactions in the rumen of ruminants. By collecting samples of the top three dominant forage grasses in the four different types of grassland in China, including typical steppes, desert steppes, meadow steppe, and alpine steppes, and combining them with corn in pairs, the nutritional fermentation characteristics and gas production kinetics were studied using rumen <italic>in vitro</italic> fermentation technology, and the comprehensive combination effect index (MFAEI) was evaluated. The results showed that most of the dominant grasses in the four types of grasslands were combined with each other, or adding corn to the grass combination could improve the digestibility of dry matter (DM), crude protein (CP), and crude fat (EE). The combination of forage can improve the neutral detergent fiber digestibility (NDFD) and acidic detergent fiber digestibility (ADFD) of forage to varying degrees. Although it does not affect the rumen fermentation parameters and gas composition ratio, and adding corn will change the structure of fermentation substrates, increase the content of short chain fatty acids such as butyric acid and ectopic acid, and increase the proportion of methane to varying degrees. Among of them, adding corn to forage combinations in typical grasslands will significantly increase the proportion of methane. Most grass combinations and their MFAEI after mixed fermentation with corn exhibit a positive combination effect. Among them, the first dominant grass in typical grasslands and desert grasslands, such as Leymus chinensis and Stipa breviflora, and the Artemisia genus grass in meadow grasslands and alpine grasslands, all show a positive effect. Therefore, by utilizing the digestion characteristics of dominant forage in different types of grasslands and leveraging the combination effect of forage, the utilization rate of forage can be improved, promoting the conversion efficiency from primary productivity (forage production) to secondary productivity (livestock production).