Microplastics in animal nutrition: Occurrence, spread, and hazard in animals

Determination of polystyrene nanospheres and other nanoplastics in water via binding with organic dyes by capillary electrophoresis with laser-induced fluorescence detection

The purpose of this research work was to develop a new method for the quantitative analysis of water samples containing nanoplastics in the presence of microplastics and other colloidal particles. Our approach involved a mixture of fluorescent organic dyes that was added to each water sample for binding with the target nanoplastics. Binding was proven by zeta potential measurements that revealed the point of zero charge shifting from pH 4 for polystyrene nanoparticles, to pH 6.13 after binding with the dye mixture. Centrifugation effectively separated the free dyes from all dye-bound particles in the heterogeneous mixture, thus eliminating any potential interference. Electrokinetic injection of the free dyes in the supernatant allowed efficient separation by capillary electrophoresis (CE), for accurate quantitation individually with laser-induced fluorescence detection. A diode laser was operated at λex of 450 nm to induce fluorescence from the dyes, and an optical interference filter to collect only emission photons with λem of 520 nm. The fluorescence peak intensity decreased for each dye, thereby determining the total binding activity of all plastics and other particles. This new method enables high-throughput screening of water samples for nanoplastics, based on their fast binding with organic dyes in 5 min, rapid analytical separation of dyes by capillary electrophoresis within 10 min, and instantaneous fluorescence intensity measurement of individual dye peaks. Binding percentages as high as 149(±2) %/μg of 9.5-nm polystyrene nanoparticles were attained when using a concentration of 125 μg/mL for each dye. The binding mechanism was mainly attributed to hydrophobic interaction and modified by electrostatic forces. Binding of the four dyes with polystyrene microparticles, casein micelles, and transition metal oxide nanoparticles was verified to demonstrate minimal interference. The method was successfully applied to rapid testing of water samples from various sources, ranging from drinking fountains and household faucets to flowing rivers. The method also applied to a decontamination study wherein a removal of 94 % polystyrene nanospheres (diameter = 80 nm) was achieved by adding only 20 mg of casein powder into 1.6 mL of water containing 36 mg of the nanoplastics initially.

Low-Density Polyethylene Microplastics in the Rumen: Implications for Rumen Fermentation Dynamics and Utilization of Concentrate Feed

Microplastics (MPs) have emerged as a significant environmental threat, infiltrating livestock systems. This study presents the first in vitro investigation of the effects of low-density polyethylene (LDPE) MP contamination on rumen fermentation dynamics and feed utilization in a simulated ruminal digestive system. Concentrate feed was incubated in buffered rumen fluid collected from lambs, supplemented with LDPE MPs at concentrations of 3.3 g/L and 6.6 g/L and compared to the concentrate incubated in the buffered rumen fluid without MP contamination. The results demonstrate that both levels of LDPE MPs significantly altered rumen fermentation dynamics by reducing asymptotic gas production by 11% and 15% and increasing the constant rate of gas production by 16% and 19% at low and high addition levels, respectively, compared to the control. However, the early-stage fermentation dynamics remained unaffected. Furthermore, both levels of LDPE MPs reduced rumen protozoal populations (20% and 23%) and ammonia-nitrogen levels by 11% at both of addition levels. Despite these disruptions, rumen pH remained unaffected. Increasing the addition level of LDPE from 3.3 to 6.6 g/L did not exacerbate the disruptions. The results of this study highlight the potential risks posed by LDPE MPs in ruminal nutrition. Further in vivo investigations are essential to validate these findings and assess their impact on animal performance.

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.