Clearance of Biodegradable Polymer and Polyethylene Films from the Rumens of Holstein Bull Calves

SIMPLE SUMMARY: Domestic and non-domestic ruminants indiscriminately ingest plastics, such as hay netting, typically developed from polyethylene. Due to their indigestible nature, plastics accumulate in the rumen when ingested and animal health and production problems arise. Therefore, it is necessary to find biodegradable materials that will break down in the rumen when consumed to replace polyethylene. In pursuit of this, we fed twelve Holstein bull calves capsules containing a biodegradable polymer, polyethylene, or nothing for 30 d and evaluated animal health. At the end of the 30 d, animals were euthanized to evaluate the rumen for potential damage and to characterize polymer residues in rumen contents. No calves presented any signs related to the building up of polymer in the rumen and animal health was not affected by any treatment. Calves that received polyethylene retained 7% of the total dosed material, while calves that received the biodegradable polymer retained less than 1%. The biodegradable residues were fragmented to 10% of their original size. Based on our results, we suggest that agricultural plastics developed from biodegradable polymers may be a potential alternative to conventional plastics in the case of animal ingestion due to their improved ruminal degradation and decreased accumulation in the rumen compared to conventional polyethylene. ABSTRACT: Due to the occurrence of plastic impaction in ruminants and its deleterious effects on health and production, it is necessary to determine the suitability of biodegradable polymers to replace polyethylene-based agricultural plastics, such as hay netting. The objectives of this study were to evaluate the clearance of a polyhydroxyalkanoate (PHA) and poly(butylene succinate-co-adipate) (PBSA) melt-blend polymer from the rumen when fed to cattle and subsequent animal health. Twelve Holstein bull calves were dosed with an encapsulated 13.6 g of PBSA:PHA (Blend), 13.6 g of low-density polyethylene (LDPE), or four empty gelatin capsules (Control) for 30 d. The feed intake, body weight, and body temperature were evaluated, and hemograms were run on d 0 and d 30. On d 31, calves were euthanized to evaluate gross rumen measurements and pathology, papillae length, and polymer residues in rumen contents. No calves presented any signs related to plastic impaction. The feed intake; body weight; rectal temperature; hematological parameters; gross rumen measurements and pathology; and rumen pH and temperature were not affected by treatments. Calves dosed with LDPE had 27 g of undegraded polymer retained in the rumen while Blend calves had only 2 g of fragmented polymers that were 10% of their original size. Agricultural plastics developed from PBSA:PHA may be a suitable alternative to LDPE-based products in the case of animal ingestion and may reduce the incidence of plastic impaction.