45. Consumption, Ruminal Degradation, and Rumen Accumulation of a Novel Compostable Hay-bale Net-wrap.

Abstract The replacement of synthetic plastic twine and net wrap with biodegradable or compostable alternatives has the potential to reduce single-use plastic waste and minimize health risks associated with accidental ingestion by livestock. A recently developed compostable net wrap [Nature's Net Wrap (NNW)] has been proposed as an environmentally sustainable alternative, although little is known about its fate following consumption by ruminants. Therefore, three studies were conducted to evaluate the ruminal disappearance and potential accumulation of the NNW when ingested by cattle. In Study 1, ruminal degradability of NNW was evaluated using in situ ruminal incubation. Grass hay alone or grass hay plus NNW (6 × 28 cm; ∼0.43 g) placed in sealed nylon bags was incubated in the rumens of four cows for 0, 1, 7, 14, 28, 56, 84, 112, and 140-d. Samples were analyzed to determine dry matter (DM) disappearance over time. In Study 2, feeding behaviour and inadvertent intake of NNW were assessed in a 7-d trial with six ruminally cannulated heifers fed grass hay containing NNW at 0.042 ± 0.005 % of diet DM following a 14-d adaptation period. On d 7 of the trial, a total rumen evacuation was performed to recover any ingested NNW still present in the rumen. In Study 3, the same heifers each received 26.2 g of NNW weekly through the ruminal cannula for four consecutive weeks. Total rumen evacuations were performed before the first insertion and 7 and 14-d after the final insertion to determine whether NNW accumulated in the rumen. In Study 1, data were analyzed using the MIXED procedure of SAS with d as a fixed effect for the evaluation of the NNW disappearance, and treatment, d, and treatment × d as fixed effects for hay disappearance, with cow included as a random effect, and significance declared at P < 0.05. The NNW DM disappearance increased over time (P < 0.01), but only 0.6% DM loss was observed after 140 d. Grass hay incubated with NNW had slightly greater DM disappearance than hay alone (P < 0.01), but no treatment × d interaction was detected (P = 0.50). In Study 2, heifers consumed 61.6 ± 11.5% of the NNW offered, and 20.6 ± 15.2% of NNW consumed was recovered upon rumen evacuation. In Study 3, of 96.1 ± 7.4% of the NNW inserted into the rumen had disappeared by 7-d, and 99.6 ± 0.8% by 14-d. Overall, NNW exhibited minimal ruminal degradation when placed in nylon bags but disappeared rapidly from the rumen when consumed freely, likely due to mechanical fragmentation from chewing and rumination, and ruminal passage. These results suggest that while NNW is not ruminally degradable, it does not appear to accumulate in the rumen when small quantities are ingested.