Grass-based feeding strategies for organic growing-finishing pigs during temperate summer conditions

Green protein can replace soy in organic pig diets without performance loss. Pigs on Green protein with fresh grass-clover have higher lean meat percentage. Grass-clover roughage intake is higher than silage, regardless of concentrate type. Fresh grass-clover provides more nitrogen, allowing reduced protein in feed. This study evaluated substituting soy press cake with Green protein—derived from biorefined grass-clover—and the provision of grass-clover-based roughage for organic growing-finishing pigs under temperate summer conditions. A total of 150 pigs were assigned to five dietary treatments combining soy or Green protein-based compound feed with either fresh grass-clover or silage. Growth performance, feed intake, lean meat percentage, and blood metabolite levels were assessed. Replacing soy with Green protein did not negatively impact growth performance and pigs fed Green protein and fresh grass-clover had higher lean meat percentage than those fed soy with silage (P<0.01). Roughage intake was greater with fresh grass-clover than with silage (P<0.01), contributing with more nitrogen (N; P<0.01). A 10% reduction in lysine in the Green protein compound feed, when paired with fresh grass-clover, did not compromise productivity and increased lean meat percentage compared to the soy-silage group. Blood metabolite levels were only minimally affected by dietary treatment. In conclusion, Green protein can replace soy in organic pig feed without compromising animal performance, offering a promising alternative. The higher lean meat percentage associated with Green protein indicated a more favourable amino acid profile for growth compared to soy. While the overall nutrient contribution from grass-based roughages remained limited, the inclusion of fresh grass-clover allowed for a reduction in Green protein-based compound feed. This adjustment could positively impact both feed cost efficiency and the reduction of nutrient leaching into the environment.