Review: Nutritional, production, and safety aspects of converting food loss and waste into feed for livestock

Agricultural activities place pressure on the environment through the demand of land, water, and nutrients, as well as the subsequent potential generation of emissions and pollutants. However, agriculture is essential to feed the growing population. Nutrient leakage from the food system in the form of food loss and waste (FLW) makes food production inefficient. The FLW refers to the deterioration of food quality anywhere in the food system that makes it unsuitable for human consumption. This includes vegetable and fruit leftovers, bakery leftovers and former foodstuffs products and properly processed food waste, depending on the legislation. A one-nutrition approach advocates for repurposing FLW into feed, thereby reducing nutrient leakage and food-feed competition. However, the evaluation of FLW in feed to produce a clear guideline for feeding FLW to livestock is not yet well established. Therefore, this review examines the use of FLW as a direct feed for livestock and FLW biotransformation via insects or microbes. These scenarios were evaluated based on their nutritional value and impact on livestock health, performance, and safety. After minimal to moderate processing of FLW, direct feeding offers a safe, nutrient-rich, and economically viable option for feeding FLW to livestock. Insects and microbes biotransform FLW into protein- and energy-rich biomass, providing macronutrients and supporting livestock performance under well-designed diet formulations and conditions. However, safety issues such as the presence of contaminants, spoilage and microbial risk in FLW can negatively impact livestock health and performance. Hence, beyond nutritional values, assessing the safety of using FLW as feed is mandatory, as discussed in this review. As of now, a full replacement of ingredients such as corn or soy is not possible due to a decrease in livestock performance in some instances and limitations in regulatory guidelines and infrastructure. This review proposes a categorisation of FLW based on the intensity of processing required to inactivate pathogens in the raw FLW, nutritional value, moisture content, logistics, and target species. The proposed categorisation offers a decision-making guideline for including FLW in feed. Further research is needed to prioritise a comprehensive assessment of the economic and environmental impacts of FLW use before reconsidering regulatory frameworks and substantially replacing conventional forage crops.