Gas production and environmental impact indicators from in vitro fermentation of diets with nopal silage (Opuntia ficus-indica L.)

Abstract

Objective: To evaluate the global warming potential index (GWPI) and in vitro gas production (GP) of diets of fattening lambs fed with silage of agricultural by-products of cactus and prickly pear (Opuntia ficus-indica L.)-hibiscus grain (Hibiscus sabdariffa L.)-oats straw (Avena sativa L.)

Design/methodology/approach: The PG technique was used to obtain the GWPI of isoproteic (crude protein (CP)) and isoenergetic diets 15%CP and 2.8 Mcal ME (metabolizable energy)): conventional diet (CD; control), with corn silage (CSD), and with 10 or 20% of cactus-prickly pear-hibiscus grain-oats straw silage (CHSD10, CHSD20), offered during 60 d to 24 fattening bighorn sheep.

Results: Although in vitro dry matter digestibility at 72 h (IVDMD₇₂) was better in CSD, it was similar for CHSD10, CHSD20, and CSD. CHSD10 and CHSD20 had the lowest CH₄ production, GWPI, and environmental impact index (EII). The low fermentable fraction (LF; GP=24-72 h) was related to IVDMD₇₂.

Findings/conclusions: The cactus pear-hibiscus grain silages inclusion had the same IVDMD₇₂ that conventional diets but decreased the CH₄ emissions and the GWPI.