The inclusion of salty and sugary food leftovers in the feed of growing and finishing pigs does not impair the diet digestibility

A more sustainable feeding strategy in pig production needs to be achieved in terms of reducing food waste and environmental footprint. One of the potential alternatives is the reintroduction into the feed chain of the food industry leftovers, also known as ex-food or Former Food Products (FFPs). The presence of manufacturing errors, packaging defects, and logistic challenges, makes these products no longer suitable for the human market. Due to the richness in lipids, starch and energy, FFPs-based diet could meet the needs of growing and fattening pigs. In this study FFPs were divided in two main categories (sugary and salty) and they were used in growing-finishing’s diets in order to replace conventional ingredients and investigate their effects on diet digestibility. Thirty-six Swiss Large White male castrated pigs were assigned to the three grower and finisher experimental diets: 1) standard diet (ST-G; ST-F), 0% FFPs; 2) 30% conventional ingredients replaced by sugary FFPs (SU-G, SU-F); 3) 30% conventional ingredients replaced by salty FFPs (SA-G, SA-F). The grower and finisher diets were formulated to be iso-energetic and iso-nitrogenous. Fecal samples from 24 selected pigs (eight pigs from each treatment) were collected to assess the apparent total tract digestibility (ATTD) of gross energy (GE), crude fiber (CF), and crude protein (CP). ATTD were calculated for both the growing and finishing phases. Data were analyzed with the MIXED procedure of SAS. The model used included the dietary treatments as fixed effect and the pigs as random effects. Least squares means were calculated and considered statistically significant at P < 0.05. In both the growing and finishing periods, the energy digestibility of the SA diets was greater (P < 0.05) than that of the ST diets, with intermediate values for the SU diets. In the finisher but not the grower period, the crude fiber digestibility of the ST diet was greater (p < 0.05) than that of the SA and SU diets. The crude protein ATTD did not differ among the groups. Despite the digestibility of energy, CF and CP were affected by dietary treatments in different ways, this study confirms that the inclusion of 30% FFPs in the feed of growing-finishing pigs do not have any detrimental effects on diet digestibility.