PSXIII-B-2 - Clearance of Poly(butylene succinate-co-adipate):polyhydroxyalkanoate and Low-density Polyethylene Films from the Rumens of Holstein Bull Calves

Abstract: Replacing undigestible, polyethylene-based agricultural plastics like net wrap with biodegradable alternatives polyhydroxyalkanoate (PHA) and poly(butylene succinate-co-adipate) (PBSA) may reduce the incidence of plastic impaction in ruminants. The objectives of this study were to evaluate the ruminal clearance of PBSA:PHA compared to low-density polyethylene (LDPE) and to evaluate animal health when these materials are fed. Twelve Holstein bull calves, blocked by age and weight, were randomly allocated to one of three daily bolus treatments for 30d: 13.6g of PBSA:PHA in 4 capsules (Blend), 13.6g of LDPE in 4 capsules (LDPE), or 4 empty capsules (Control). Hemograms were conducted on blood samples collected on d0 and d30. On d31, animals were sacrificed to evaluate gross rumen measurements, pathology, and papillae length, and to characterize polymer residues in rumen contents. Data were analyzed with PROC MIXED in SAS and least squared differences were adjusted by Tukey’s method. No animals presented any symptoms related to plastic impaction and animal health was not affected by treatment. Daily grain and hay intake, body weight, rectal temperature, hematological parameters, gross rumen measurements and pathology, and rumen pH and temperature were not affected by treatment. Methylene blue reduction time of Blend calves tended to be decreased by 30% compared to LDPE calves (P=0.06), and caudal ventral papillae length of Blend calves were 50% longer than those of Control animals (P< 0.01). Thus, PBSA:PHA may have beneficial impacts. Calves dosed with LDPE retained 27.42g of undegraded polymer in the rumen while 1.72g of fragmented polymers 10% of their original size were detected in Blend calves (P< 0.01). Our results indicate that if net wrap is developed from PBSA:PHA and incorporated into ruminant feed, aggregation of filamentous material will not occur in the rumen, and incidences of plastic impaction will be decreased compared to net wrap developed from LDPE.