PSXI-5 - Transforming Retailer's Food Waste into Silage for Sustainable Animal Nutrition.

Abstract: Food waste (FW) represents a major environmental and socio-economic problem. In Canada, about 11.2 million metric tons of avoidable food waste is produced yearly. An alternative to reduce this impact would be preserving a greater proportion of this, for livestock feed. Therefore, the objective of this study was to use discarded fruits, vegetables, and bakery products from retailers (FW), ensile them, and assess their nutritional value and contribution to a sustainable livestock feed supply. For this, two treatments for reducing the moisture content of FW were evaluated: Sun-dried (SD), and Passive-dried (PD), were compared to Control (C), using laboratory mini-silos over 60 d of ensiling. Although dry matter (DM) increased by 1-5% for PD and SD, respectively, up to 41.9% of bread products were required to produce a targeted silage DM of 38%. Silage aerobic stability was assessed during 20 d exposure to air. Chemical analyses (pH, volatile fatty acids, lactic acid, ammonia) were assessed in pre-fermentation (D0), and post-fermentation (D60). Nutritional quality was evaluated according to AOAC standard methods. Statistical analyses employed mixed models for nutritional and fermentation data, with drying treatments (C, PD, SD) as fixed effects. All mature silages were high in crude protein (15.2 to 15.7%), crude fat (6.0 to 6.3%), sodium (0.48 to 0.52 %), sugars (WSC; 0.95 to 1.53 %), and low in neutral detergent fiber (6.2 to 7.6%) as compared to traditional silages used as livestock feed. Fermentation parameters showed that lactic acid content was higher than acetic acid, and pH decreased from a maximum of 5.26 at D0 to a minimum of 3.85 at D60. Mycophenolic acid was the only mycotoxin above the limit of detection in D0 silage, with all mycotoxins below reference concentrations at D60. Plate counts of molds and yeasts declined (P < 0.001) by 5-7 log colony-forming units (CFU) over 60 d of fermentation and were not detected in mature silage. Silage showed aerobic stability after 20 days of aerobic exposure (pH 3.86+0.027). In conclusion, ensiling FW could be a viable way of converting low-value waste products into good-quality feed. However, approaches other than SD and PD are required for increasing silage DM as insufficient bread products may be available for this purpose in all batches of FW. Further study of palatability along with digestibility testing will be needed for a scaling-up process.