Glycerol may not always be effective as a nutritional strategy to reduce methane production. Likewise, glycerol did not decrease lipolysis sufficiently to limit the intense biohydrogenation of unsaturated fatty acids in the rumen fluid, hence would possibly not increase the healthy UFA deposition in meat and milk. Our findings also indicate that the effect of glycerol on ruminal fermentation may depend on differences in the fatty profiles of different lipid sources. Therefore, they pave the way for further research using other sources of lipids, or alternative forms of lipid protection. Indeed, soybean and linseed oil have a high cost owing to the costly extraction process. Alternatively, feeding the animals with these vegetable oils in the form of seeds could reduce costs while ensuring a lower ruminal biohydrogenation.