In vitro rumen fermentation characteristics of substrate mixtures with soybean meal partially replaced by microbially fermented yellow wine lees

Abstract

This study was conducted to evaluate the effects of replacing soybean meal (SBM) with unfermented and microbially fermented yellow wine lees (YWL) mix on the in vitro rumen fermentation characteristics of substrate mixtures. Both types consisting of YWL at 400 g/kg were included in the mixtures at different ratios (1:0, 1:1, 1:2, 1:5 and 0:1, w/w) to replace SBM. Microbial fermentation of YWL did not have a negative impact on gas value (p> .05), increased microbial protein (MCP, p < .01) and in vitro crude protein (CP) digestibility (p < .01), and improved the efficiency of nitrogen utilisation (p < .01). The ratio of YWL replacing SBM had linear and quadratic effects on gas production (GP, p < .01), the rate of GP (p < .01), MCP (p < .01), total volatile fatty acids (VFAs, p < .01), in vitro CP digestibility and efficiency of nitrogen utilisation (p < .01), with the optimal ratio at 1:1. The in vitro digestibilities of dry matter and organic were slightly (p < .01) reduced with the increasing ratio of YWL. Besides, positive associative effects were observed on GP parameters, VFA and MCP at some replacement ratios. Considering the in vitro rumen characteristics and their associative effects, the optimal ratio at which to replace SBM with microbially fermented YWL was indicated to be 1:1. Highlights The in vitro rumen fermentation characteristics performed better with microbially fermented than unfermented yellow wine lees (YWL) replacing soybean meal (SBM). The positive associative effects were observed on gas production parameters, volatile fatty acid and microbial protein at replacing ratio of 1:1. The optimal ratio at which to replace SBM with microbially fermented YWL was 1:1.