Potential Use of Tropical and Subtropical Fruits By-Products in Pig Diet: In Vitro Two-Step Evaluation

Pineapple (<i>Ananas comosus</i> L.), cashew (<i>Anacardium occidentale</i> L.) and mango (<i>Mangifera indica</i> L.) are among the most cultivated plants in tropical and subtropical regions due to the high demand around the world. Following the harvesting and processing of pineapple, cashew and mango fruits, a huge amount of waste is generated, which is generally discarded into the environment, contributing to global pollution and water contamination. This study aims to propose alternative feeds for pigs by characterizing cashew, pineapple and mango fruit by-products through an in vitro two-step (gastro-intestinal and caecum) study to provide feeds not competing with humans and promoting eco-sustainable livestock. Ten by-products [i.e., pineapple peel and pomace; cashew nut testa, cashew (var. yellow) whole fruit and pomace; cashew (var. red) whole fruit and pomace; mango peel, kernel and testa] were sampled in Benin. The samples involved chemical analysis and an in vitro two-step digestion method (enzymatic + microbial digestibility). The results report a low dry matter (DM) content specifically in the pomace, peel and whole apple (13.0-27.2%), while higher lipids were observed for cashew nut testa and mango kernel (26.4 and 11.2% DM). The investigated by-products fall within the interval of referenced feeds for structural carbohydrates (NDF: 7.6-47.1% DM) and protein (6.21-51.2% DM), except mango by-products with a low content of protein (2.51-4.69% DM). The total dry matter digestibility, short-chain fatty acid and gas production were low for cashew by-products and stopped after 48 h of incubation. Pineapple pomace, cashew whole apple, pomace and testa can be considered as feedstuff in fattening pigs, presenting characteristics partly similar to beet pulp. Indeed, mango peel and kernel should be combined with a protein feed source to feed pigs. Presently, fruit by-products, such as those from cashew, pineapple and mango, are thrown into the environment, contributing to global warming and water pollution. These problems would be reduced by recycling these wastes in other fields, such as pig nutrition, creating a circular economy to provide feeds promoting eco-sustainable livestock. Indeed, in vivo studies are needed before proposing these by-products for pig diets.