The recycling of tropical fruit peel waste-products applied in feed additive for ruminants: food manufacturing industries, phytonutrient properties, mechanisms, and future applications

Tropical fruits are grown on tree varieties native to tropical regions, presenting a high concentration of phytonutrients (PTNs). Tropical fruits are often used in the extraction of juice, as well as in the preparation of jams, jellies, and canned products. The residual components, particularly fruit peels, are frequently discarded as wastes. This approach intends to reduce waste accumulation while meeting the growing public demand for PTNs, which are believed to possess antibacterial, antioxidant, methane production inhibitory, and rumen fermentation-enhancing properties. The tropical fruit wastes under consideration include banana, citrus fruit, dragon fruit, durian, jackfruit, mango, mangosteen, passion fruit, pineapple, pomegranate, and rambutan. Therefore, the objective of this review is to provide a comprehensive overview of the existing research focusing on the biological capabilities of tropical waste products derived from fruit peels, as well as their PTN profile, targeting their potential as supplements as feed additives for ruminants. The main attention of using PTNs found in tropical fruit peels is for enhancing rumen fermentation characteristics and production, while simultaneously mitigating the methane (CH4) production. Results provided by the present review showed that fruit peel waste products could buffer rumen pH levels, improve nutrient digestibility, ammonia-nitrogen (NH3-N) concentrations, blood urea nitrogen (BUN) levels, volatile fatty acids (VFAs) concentrations, and microbial populations, as well as enhancing milk production, and decrease CH4 production. These waste products could be a potential alternative plant-based PTN compound supplement to be use as a feed additive in ruminants.