Valorisation of Selected Fruit Pomaces in Animal Nutrition

Rising feed costs and the shift towards circular bioeconomy systems have generated interest in agro-industrial by-products as livestock feeds, but the evidence on fruit pomaces is fragmented across single pomaces, single species and single processing methods. This review compares apple, citrus and grape pomaces against a common set of nutritional, processing, functional and environmental criteria, and grades the strength of the evidence supporting each comparison. Under particular species-, processing- and dose-specific conditions, properly prepared pomaces have been reported to improve ruminal fermentation, nutrient digestibility, milk composition and oxidative status in ruminants, and gut health, antioxidant status and product quality in non-ruminants. Responses are heterogeneous, and null or adverse effects on intake, digestibility and performance also occur, particularly at high inclusion levels and with lignin- and tannin-rich material. Reductions in enteric methane have been measured in vivo for grape by-products in dairy cattle, whereas the evidence for citrus flavonoids remains in vitro; whole-system environmental and economic benefits are unquantified. Research priorities include standardised processing and compositional reporting, routine control of mycotoxins, pesticide residues and heavy metals, species-specific dose–response trials, and whole-chain techno-economic and life-cycle assessment.