Impacts of liquid milk permeate supplementation on rumen microbial fermentation and community structure in an in vitro semi-continuous culture system

We investigated the potential of liquid milk permeate as a microbial energy source, in an in vitro semi-continuous culture system, and its impact on rumen microbial communities. Sixteen fermenters in a 2 × 4 randomized complete block design, over two 14-day periods to assess the impact of 50 mL/day of various liquids (C: control, no liquid; W: water; PW: 50:50 water:permeate; P: permeate) under two buffering conditions (N: normal; S: subacute ruminal acidosis). The V3–V4 region of the 16S rRNA gene was sequenced using Illumina MiSeq. Data analysis in R examined the effects of treatments on microbial taxa, pH, and short chain fatty acids (SCFA). Water addition did not significantly affect pH, gas production, or SCFA proportions ( p ≥ 0.05) but reduced NH 3 concentration in both buffer conditions ( p ≤ 0.001). Permeate lowered pH and NH 3 in both buffering conditions ( p ≤ 0.001) and altered microbial composition without negatively impacting bacterial diversity. These findings suggest that water can be added to a semi-continuous in vitro system without disrupting microbial balance, enhancing model accuracy. Permeate can be a source of energy in liquid form but it must be balanced with adequate protein to avoid reductions in NH 3 .