The growing biofuel industry generates by-products that have shown promise as energy and protein feeds in ruminant diets. The objective of this project was to determine the effects of by-products of biodiesel production, obtained from different sources of oilseeds, on the in vitro degradability of nutrients, in vitro ruminal fermentation and methane gas production. Palisadegrass ( Brachiaria brizantha) was used as a model. Its isolated incubation was considered as a control and the treatments consisted of its combination with twelve biodiesel by-products, as follows: 1) cotton cake ( Gossypium hirsutum); 2) sunflower cake ( Helianthus annuus); 3) castor bean cake ( Ricinus communis); 4) moringa cake ( Moringa oleifera); 5) purging nut cake ( Jatropha curcas); 6) soybean cake ( Glycine max); 7) canola cake ( Brassica napus); 8) black sunflower cake ( Helianthus annuus); 9) forage turnip cake ( Raphanus sativus); 10) glycerin in a 7:3 ratio (70% palisadegrass and 30% glycerin); 11) glycerin in a 5:5 ratio; and 12) glycerin in a 3:7 ratio. Samples of each treatment were incubated in vitro, in a water bath, for 48 hours and removed after 6, 12, 24 and 48 hours, to determine the cumulative production of methane gas (mL/g of dry matter incubated). Methane production (mL/g) and dry matter disappearance were measured at 6 and 12 hours post-incubation. Crude protein concentrations ranged from 121 to 577 g/Kg and Fiber in Neutral Detergent concentrations ranged from 202 to 652 g/Kg. After 48 h, pH and in vitro dry matter degradability were affected by different levels and supplementations. The castor bean cake treatment had the lowest dry matter degradability index, but resulted in a soluble fraction comparable to that of the control. The treatments with moringa and sunflower cakes exhibited rapid degradation rates, both in crude protein and in dry matter. In addition, both treatments showed the highest crude protein degradability compared to other food sources. The results suggest that the by-product of moringa seed oil extraction can be included in ruminant diets to reduce methane production without affecting nutrient degradability. The generated data can be used in the future in the calibration of a mathematical model for the evaluation of animal performance under different diets.