Oyster mushroom bioprocessing enhances the nutritional value of olive pomace for ruminants

Abstract

Incorporating olive pomace (OP) into ruminant feed can alleviate the environmental impact of OP disposal, minimize food–feed competition, and bolster food security. However, high fibre and low crude protein (CP) reduce its nutritional value for ruminants. The study assessed the effect of oyster mushrooms (OYM) on the nutritive value of OP. To this end, chemical composition and in vitro ruminal fermentation parameters of spent OP substrate were evaluated. The OYM was spawned on 200 g OP at the rate of 0 (OP0), 10 (OP10), 20 (OP20), 30 (OP30), 40 (OP40), and 50% w/w (OP50) and cultivated for 35 d with 10 replicate pots per spawning rate. Dry matter, organic matter, CP, and ash increased linearly, whereas neutral detergent fibre and crude fat declined linearly. In vitro cumulative gas production at 12, 24, 36, 48, 72, and 96 h showed a positive quadratic response. Spawning rates linearly enhanced the immediately fermentable fraction (a) and rate of gas production from the slowly fermentable fraction (c), while the partitioning factor increased linearly. Positive quadratic responses were noted for the slowly fermentable fraction, potential gas production, effective gas production, and in vitro organic matter degradation at 96 h of ruminal incubation. In conclusion, OYM enhanced the nutritive value of OP by reducing fibre content, a, and c fractions while improving CP content and fermentation efficiency. This approach facilitates the bioconversion of OP into sustainable ruminant feed, leading to lower feed costs, addressing waste disposal issues, and creating supplementary income for the olive oil industry.