| Summary: | Abstract Background The high amount of soluble carbohydrates and the reduced dry matter content in cactus pear can cause excessive fermentation, resulting in nutrient losses, when it is preserved in the silage form. Thus, the association of cactus pear with elephant grass in the production of mixed silages may reduce nutritional losses during the ensiling process. Thus, the aim was to evaluate the mineral profile, carbohydrates fractionation, nitrogen compounds, and in vitro gas production of elephant grass silages associated with a cactus pear levels (0, 150, 300, and 450 g/kg on dry matter basis). The study was carried out in a completely randomized design, with 4 treatments and 5 replications, totaling 20 experimental silos. Results The increase in cactus pear levels in elephant grass silages composition provided an increase in the contents of K (P = 0.013), Ca (P < 0.001), Mg (P < 0.001), Na (P = 0.001), B (P = 0.044) and Zn (P = 0.016), reduced P (P = 0.039) and promoted a quadratic effect for Fe (P = 0.045) content. The addition of cactus pear levels in elephant grass silages increased the total carbohydrates (P < 0.001) and A + B1 fraction (P = 0.002) and promoted a quadratic effect for B2 fraction (P = 0.032). For nitrogen compounds, the increase in cactus pear levels in elephant grass silages composition reduced the B1 + B2 fraction (P = 0.002) and increased the C fraction (P = 0.007). There was no effect of cactus pear levels on the in vitro gas production of elephant grass silages (P > 0.05). Conclusions Under the experimental conditions, the addition of cactus pear in elephant grass silage at levels up to 450 g/kg dry matter does not affect the in vitro gas production, however, it improves the mineral profile, contributes to the increase in the total carbohydrate content and the A + B1 fraction in the silages. Besides this, cactus pear addition reduces the B1 + B2 protein fraction, increasing the fraction C content in the silages, suggesting the necessity to supply an additional soluble nitrogen source for good ruminal functioning.
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