Effect of Microplastic Contamination on In Vitro Ruminal Fermentation and Feed Degradability

This study examined the effects of microplastic (MP) contamination on rumen fermentation dynamics and concentrate degradability using an in vitro model with lamb rumen fluid. Three types of MPs—polyethylene terephthalate (PET), low-density polyethylene (LDPE), and polyamide (PA)—were tested at contamination levels of 0%, 0.6%, 1.2%, and 1.8% of dry matter. MP contamination significantly disrupted rumen fermentation dynamics, reduced feed degradability, increased gas production, accelerated fermentation rates, and shortened the lag time before gas production (p < 0.05). Additionally, MPs impaired microbial efficiency, increased ammonia-nitrogen (NH₃-N) levels, decreased rumen protozoa populations, and reduced concentrate degradability (p < 0.05). LDPE exhibited the most severe effects, causing the highest increases in gas production and NH₃-N levels (15% and 12%, respectively at LDPE highest dose) while decreasing microbial efficiency, protozoa count, and feed degradability (16.0%, 16.4%, and 4.5%, respectively at LDPE highest dose). The severity of MPs' impacts followed a significant linear trend, with higher concentrations leading to more pronounced negative effects. The findings highlight MPs as significant emerging pollutants that can adversely affect rumen function and animal nutrition.