Impact of Micro Plastics on Ruminant Digestion

A recently published article has provided some early indications of a negative impact of polyethylene terephthalate micro plastics (PET MPs ) on ruminant digestive systems. PET MPs are a common type of plastic, which is increasingly reported as an environmental contaminant. The work¹, exposed rumen contents obtained from Piedmontese bulls to a mixture of hay contaminated with PET MPs at various concentrations. The results are concerning in that, in this in vitro testing system, a significant  reduction in the digestion of crude protein, of between 9 and 16%, was reported. The higher the concentration of PET MPs in the diet, the greater the impact on digestibility.  The plastics also appeared to inhibit the breakdown of fibre, as measured by neutral detergent fibre (N.D F.), by a similar amount. Lower concentrations of PET MPS were shown to have an impact on protein digestibility in the gastro-intestinal phase of digestion. 

Reports of increasing concentrations of PET MPs in ruminant faeces and general environmental contamination are increasing and concerns about their potential impact has grown. Another recent study in pigs, has shown inflammation and shortening of micro-villi lining the intestine of pigs exposed to the plastics². The authors of this study also warn of the potential for reduced productivity and animal health issues linked to chronic inflammation. 

This is the first paper that has indicated some negative impacts from this exposure on the digestive system of ruminants. The authors hypothesise that this result could be linked to negative impacts on rumen microbiota or digestive enzymes. The implications of this reduced digestive efficiency are widespread, including reduced productivity and growth rates, as well as increased levels of environmental contamination from undigested protein and other environmental pollutants. The overall impact upon the carbon footprint of the animal production system will also be negative in that reduced efficiency of digestion will lead to increased unproductive methane generation.

Admittedly there is still much work to do to further assess this worrying trend but this early result provides sufficient evidence for continued investigation and adds to the growing demand for measurement and reduction of micro plastics in the environment. It is somewhat ironic that this paper has been published not long before an international conference failed to arrive at an agreeable plastic reduction policy³.