The present study aimed to evaluate the chemical composition, profile and fermentative losses, microbial population and the aerobic stability of mixed silages of cactus pear and gliricidia. the treatments corresponded to the addition levels of gliricidia (Gliricidia sepium (Jacq.) Steud), in the silages of cactus pear (Opuntia ficus indica Mill.), at ratios 0%, 25%, 50%, 75% and 100% gliricidia. The data were subjected to analysis of variance and regression to evaluate the effect of the addition levels of gliricidia. the average related to the opening days were compared by the tukey's test and the average hours of exposure to air were compared by the Student's t-test. the addition of gliricidia in cactus pear silage provided a linear increasing effect for pH, crude protein (CP), neutral detergent fibre (NDF), acid detergent fibre (ADF), acid detergent lignin (ADL), neutral detergent insoluble protein (NDIP), and increased aerobic stability (AS). The highest dry matter recovery was estimated in the silages with 58% gliricidia. Based on the fermentative, chemical composition and silage losses, all the silages tested were adequate. However, considering aerobic stability, the addition of at least 25% gliricidia is recommended to provide the animal a feed with important quality and high nutritional value.Both from the productive point of view of the palm and the conservation of the forage nutritional value, cactus pear ensilage would maximize the use of this forage resource, allowing farmers to create a new alternative for the conservation of feed rich in water and energy 1,2 . Cactus pear silage is even more valued for use in feeding ruminants in arid and semi-arid regions, that according to Souza et al. 3 and Borges et al. 4 the inclusion of cactus silage in the ruminant diet reduce water intake, and decrease human-animal competition for water in arid and semi-arid environments where water resources are limited. Furthermore, cactus pear silage allows harvesting of the entire palm planting, standardizing and increasing the regrowth capacity and hence productivity, besides reducing labour with harvest and periodic supply throughout the dry season.Despite some attributes unfavourable to silage, other characteristics of cactus pear as its bioactive compounds should be considered. The cladodes of the cactus pear are chemically modified structures, composed by chlorophyll and a large percentage of water internally, which exerts the photosynthetic functions of the leaves 5 , as well as the percentage of organic acids found in cladodes, which are oxalic, malic, citric, malonic, succinic and tartaric acid, the latter two being smaller 6 and showing great variation, especially when evaluated in relation to the planting site and cultural practices.Another aspect to be evaluated in the cactus pear ensiling process is related to its percentage of water soluble carbohydrates (WSC), since cactus pear is a forage rich in pectic polysaccharides 7 , i.e., esterified sugars with a high concentration of galactose, arabinose, xylose an...