Novel biodegradable plastics in sheep nutrition 1. Effects of untreated plastics on digestibility and metabolic energy and nitrogen utilization

The potential for nutritional use of the novel biodegradable polymers polyc aprolactone (PCL) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) T vas tested in sheep. Six wethers were fed at approximately maintenance leve l on hay and corn meal diets (1:1) supplemented with 0 (C) or 8% barley str aw meal (S), PCL (P1) and PHBV (P2), respectively, according to a Latin squ are design. Gross energy contents were 28.8 and 23.2 MJ per kg dry matter ( DM) for PCL and PHBV, respectively. A simultaneous measurement of respirato ry exchange and excretion was carried out. The results provided direct and indirect evidence for a low digestibility of the biodegradable plastics. Th e average PHBV digestibility coefficient was 0.04. Faecal energy losses wer e 5% higher for the biodegradable plastic-supplemented diets compared with C. The energy digestibility coefficients significantly decreased from 0.72 for C to 0.70, 0.65, and 0.67 for S, P1 and P2, respectively. The average n eutral detergent fibre digestibility was 0.61, 0.57, 0.59, 0.53 for C, S, P 1, and P2, respectively, with C and P2 significantly differing. The balance data also indicated a similarly low digestibility for PCL as that for PHBV . The metabolizable energy concentration was intermediate for S and lower ( p < 0.05) for P1 and P2 in comparison with C (11.3, 10.7, 10.6 and 10.4 MJ/ kg DM for C, S, pi and P2, respectively). The energy loss via urine and met hane did not show significant differences between the treatments. Nitrogen digestibility was not affected by biodegradable plastic consumption.