The use of sugary and salty food industry leftovers as alternative to cereal grains does not affect the growth performance in growing and finishing pigs

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 growth performance. 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. The body weight of all animals was monitored weekly starting from birth and right before the slaughter. In addition, the total feed intake (FI), the average daily gain (ADG), the average daily feed intake (ADFI), the feed conversion ratio (FCR) and the gain to feed were calculated for both the growing and finishing phases. These measurements were carried out to evaluate the growth performance of the animals according to the different experimental diets. 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. The results showed that the feed efficiency in terms of FCR was significantly higher (p < 0.05) in grower pigs fed ST diet than those fed the SA and SU diets, even though the days on feed, total FI, the ADFI were similar between the groups. However, when considering the overall mean of the entire period (growing-finishing), the use of FFPs did not affect the growth performance of pigs. In particular, BW, ADFI, ADG and FCR were similar between the three groups (p>0.05). In conclusion, no detrimental effects on growth performance are present when sugary and salty FFPs are included in the diets of growing pigs and finishing pigs up to 30%.