IN VITRO METHANE PRODUCTION AND IN SITU DEGRADABILITY OF PRICKLY PEAR PRETREATED WITH YEAST CULTURES

Background. Natural cycles and increases in temperature and droughts worldwide are being caused by the climate change effect. In addition, greenhouse gases (GHG) produced by anthropogenic causes are released to atmosphere. In this way, ruminants contribute with 30% of the total methane produced, whereas in Mexico this value represents over 50%. Since droughts are more frequent, production of forage sources which require more water are decreasing alarmingly. Due to the latter, researchers are looking for alternative forages which may alleviate this issue; Opuntia ficus-indica arises as a good forage source. Objective. To evaluate the effect of the solid state fermentation (SSF) of prickly pear with yeast cultures on in vitro gas production, ruminal fermentation parameters and in situ degradability. Methodology. Three experimental treatments were evaluated: solely prickly pear without previous SSF with yeast cultures (PP) as a control; PP+SC, previously fermented with Saccharomyces cerevisiae; and PP+KM, previously fermented with Kluyveromyces marxianus ITD00262. Treatments were fermented with ruminal liquor and dry matter and protein degradabilities, as well as ruminal fermentation parameters and gas production kinetics were measured. Results. The results obtained showed that total degradability of DM increased due to yeast pretreatment (p<0.05). Crude protein degradability and total VFA decreased with PP+SC; however, PP+SC increased total gas production (p<0.05). Otherwise, PP+KM increased propionate production and decreased methane and CO2 production (p<0.05). Implications. The information presented in this research is focused in the use of PP pretreated with yeast strains in order to increase the nutritional value by increasing its protein content. In addition, the presence of yeast cultures in feedstuffs contributes to decrease the methane synthesis in rumen. Additionally, the use of PP in arid and semiarid zones may increase the water availability for ruminants. Conclusion: The use of PP pretreated with strains of Kluyveromyces marxianus into livestock feeding increases the protein availability and contributes to a reduction in the in vitro methane synthesis in 23%.