Biological enrichment of mustard oil cake by solid-state fermentation using lactic acid bacteria and its impact on rumen fermentation

Mustard oil cake (MOC) is a protein-rich agro-industrial by-product with potential as an animal feed ingredient; however, its utilization is limited by anti-nutritional factors and reduced nutrient availability. The present study evaluated the effect of solid-state fermentation (SSF) using a Lactobacillus consortium (Lactobacillus plantarum and Pediococcus acidilactici) on the nutritional quality and in vitro rumen fermentation characteristics of MOC. Fermentation was carried out at 37 °C for 72 h, and fermented mustard oil cake (FMOC) was analysed for pH, lactic acid production, chemical composition, and rumen fermentation parameters. The pH decreased significantly from 5.66 to 4.35, while lactic acid concentration increased from 47.18 to 667.04 µg/mL, confirming successful fermentation. Fermentation significantly increased crude protein content (30.55% to 35.96%) and reduced crude fibre (5.86% to 4.72%) and ether extract (8.52% to 7.16%). in vitro evaluation revealed significantly higher net gas production (34.00 ml), dry matter digestibility (66.08%), organic matter digestibility (68.27%), ammonia nitrogen (10.20 mg/dL), and total volatile fatty acids (89.87 mM/L) in TMR containing 100% FMOC compared to control. These improvements indicate enhanced microbial fermentation, nutrient availability, and substrate utilization. The results demonstrate that solid-state fermentation using lactic acid bacteria effectively improves the nutritional value and rumen fermentability of mustard oil cake, making it a promising strategy for sustainable utilization of oilseed by-products in ruminant feeding.