Nutritional value of crude and partially defatted olive cake in finishing pigs and effects on nitrogen balance and gaseous emissions

Abstract By-products from the food industry can be valuable ingredients in animal feeds. One example is olive cake (OC), generated in large amounts by the olive oil industry, which contains oil with a high proportion of oleic acid and polyphenols. An experiment was performed using pigs to determine the nutritional value of crude (COC) and partially defatted (PDOC) olive cake, and to evaluate their effect on nutrient balance, slurry properties and potential ammonia (NH 3 ) and methane (CH 4 ) emissions. Five experimental feeds were designed; a basal diet and another four diets produced by substituting 100 or 200 g/kg of the basal diet with either COC or PDOC. Thirty finishing male pigs (76.1 ± 4.2 kg initial BW) were used in the experiment (6 animals/treatment). After a 14-day adaptation period, faeces and urine were collected separately for 7 days to measure nutrient digestibility and the excretory patterns of nitrogen. Potential NH 3 and CH 4 emissions were measured in reconstituted slurry samples over 11 and 100 days, respectively. The dry matter (DM), crude protein (CP), cellulose, starch and energy coefficients of total tract apparent digestibility (CTTAD) were negative and linearly (P 3 emissions per volume of slurry and in a lower biochemical CH 4 potential. Although slurry excretion increased with OC inclusion, daily NH 3 emissions still decreased with increasing OC inclusion. However, potential CH 4 emissions per animal increased. A global perspective throughout the production chain is needed to assess the impact of including OC in pig diets on gaseous emissions.