Digestibility of some conventional and non-conventional feedstuff and co-products to be used in liquid feed growing-finishing pigs

Two different in vivo digestibility experiments were conducted to investigate the potential value of some co-products from food and agro-industries in liquid feed diets. In the first experiment, four conventional co-products (liquid bakery co-product, brewery co-product, hominy feed and high-moisture corn) were studied by the difference method with an inclusion of 50% (in dry matter basis) to the basal diet (2.7:1 water:DM ratio). A total of 30 finishing pigs (initial body weight, BW, of 86 kg) were individually allotted and distributed to the four co-products and a control diet without co-products (n = 6). The second experiment was divided into four trials for the study of four non-conventional co-products (mayonnaise, almond meal, cocoa meal and kiwi co-product). Non-conventional co-products were studied by the regression method with increasing levels of inclusion (2%, 4%, 7% and 10%, except for kiwi, at 4%, 8%, 12% and 16%) to the feed (2.7:1 water:DM ratio) with 16 growing pigs individually allotted in each trial (initial BW 40 kg; n = 4). The chemical composition of the co-products showed that the most energy-rich co-products were mayonnaise (8.7 Mcal/kg) and almond meal (7.5 Mcal/kg), the highest high-protein co-product was brewery co-product (27%), and almond meal, liquid bakery and high-moisture corn had low levels of fiber fractions. In contrast, cocoa meal, kiwi and brewery had higher crude fiber and neutral detergent fiber levels (>5% and ≥20%, respectively). The dry matter digestibility (DMd), organic matter digestibility (OMd) and gross energy digestibility (GEd) values were less than 80% for high-moisture corn, liquid bakery co-product, mayonnaise and almond meal but did not reach 80% for brewery co-product, hominy feed, cocoa meal and kiwi. The ether extract digestibility (EEd), crude protein digestibility (CPd) and fiber fractions digestibility follow a similar tendency among co-products. The standard errors of the digestibility values obtained by regression were higher than those obtained by difference. It may be concluded that mayonnaise, almond meal, liquid bakery co-product and high-moisture corn have a high potential for being used in liquid diet for pigs. However, brewery co-product, hominy feed, cocoa meal and kiwi, if used, should be included in low levels, due to their high fiber content.