Sugary and salty former food products in pig diets affect energy and nutrient digestibility, feeding behavior but not the growth performance and carcass composition

Former foodstuff products (FFPs) are promising alternative ingredients for reducing the waste of natural resources and the environmental impact of food production. This study investigates the effects of salty and sugary FFPs on growth performance, apparent total tract digestibility (ATTD), and growing-finishing pigs' empty body and carcass composition. Thirty-six Swiss Large White male castrated pigs were assigned to three growing (G) and finishing (F) diets: 1) standard diet (ST), 0% FFPs; 2) 30% conventional ingredients replaced by sugary FFPs (SU); and 3) 30% conventional ingredients replaced by salty FFPs (SA). Fecal samples from 24 selected pigs were collected to assess the ATTD of gross energy, crude fibers, and CP. The BW was measured weekly, while feed intake was determined daily. Average daily gain (ADG), average daily feed intake (ADFI), feed conversion ratio (FCR), and ATTD were calculated for both the growing and finishing periods. Pigs' body composition was determined at ≥ 20 and ≥ 98 kg using dual-energy X-ray absorptiometry. In the growing but not finishing period, the FCR was lower (P<0.05) in ST compared to SA and SU pigs. Considering the entire growing and finishing period, neither the inclusion level nor the type of FFPs influenced (P>0.05) ADG, ADFI, FCR, or BW at slaughter. In both the growing and finishing periods, the gross energy ATTD was higher (P<0.05) in the SA than in the ST group, with intermediate values in the SU group. In the growing period, the CP ATTD was higher (P<0.05) in the SA than in the SU and ST groups. In the finishing period, the crude fibre ATTD was lower (P<0.05) in the SA and SU than the ST group. Throughout the overall period, the average daily fat intake was higher (P<0.05) in pigs fed a SU diet, even though both categories of FFPs had no (P>0.05) effects on the parameters related to the pigs' body composition (e.g., average daily fat weight gain). Finally, the carcasses of the SU group had the thickest belly fat, even though the total fat content was similar among the groups. This study confirms that including FFPs has no detrimental effects on growth performance or live body/carcass composition in growing and finishing pigs.