Abstract Baling twine is commonly used to help preserve and store forage, but conventional synthetic materials, such as polypropylene, can cause risks to livestock health and the environment. Plant-based alternatives that are biodegradable and digestible may reduce these risks. Soybean hulls (SH), a highly digestible feedstuff, were evaluated as a component of a polylactic acid (PLA)-based twine. The objective of this study was to assess the ruminal digestibility of PLA/SH twines with 0%, 10%, 20%, and 30% SH (SH-0, SH-10, SH-20, SH-30) in two mature ruminally cannulated Jersey steers. Twine samples, along with a positive control (alfalfa), a negative control (commercial polypropylene twine), and an alternative plant fiber (sisal), were incubated in situ for 0, 24, 72, 120, and 168 hours. After incubation, samples were washed, dried, and disappearance was calculated as the proportion of material lost. The fiber degradation model did not fit this dataset, so a linear regression (SAS Institute Inc., Cary, NC) was performed for each substrate to evaluate the degradation over time, where degradation (slope) is reported in percentage points per day. Alfalfa started to degrade immediately in the rumen with a slope of 5.42 ± 0.001; however, the regression was linear but did not fit the model well (P = .02; R² = 0.44), as expected. Polypropylene gained weight linearly during incubation (did not degrade; P = 0.0018, R² = 0.69) with a slope of -0.29 ± 0.00003 likely due to moisture absorption or residual dry matter. Sisal broke down steadily over time, with a slope of 8.40 and a strong linear fit (P 0.0001; R² = 0.94). Among the PLA/SH twines, SH-30 had the fastest degradability (slope = 0.0073 ± 0.00005, R² = 0.83), followed by SH-20 (slope = 0.25 ± 0.00003, R² = 0.59), SH-10 (slope = 0.08 ± 0.00001, R² = 0.49), and SH-0 (slope = -0.01 ± 0.00001, R² = 0.69). Although PLA/SH twines were not as efficiently degraded as sisal, these results suggested that incorporating soybeans into twine can improve ruminal degradability compared to conventional polypropylene twine.
Finck et al. (Wed,) studied this question.