Replacing soybean meal and maize with white lupin (Lupinus albus L.) seeds alters growth performance, rumen fermentation, fatty acid metabolism, and meat quality in growing lambs

This study evaluated the impact of replacing soybean meal and part of maize with white lupin (Lupinus albus L.) seeds in growing lamb diet on animal performance, rumen fermentation, fatty acid (FA) metabolism, and meat quality. Twenty male lambs were assigned to a control diet (CON) or to an experimental diet (LUP) in which white lupin seeds were included at 350 g/kg dry matter (DM) of the total diet. In the LUP diet, soybean meal was completely replaced and 30 % of maize was substituted with lupin seeds. Diets were formulated to be similar in crude protein content and metabolizable energy. Over 56 days, lambs fed the white lupin-based diet exhibited significantly lower feed intake, final body weight, and average daily gain compared to control, likely due to reduced palatability and the presence of antinutritional factors. Moreover, white lupin-based diet altered ruminal fermentation by increasing acetate and butyrate proportions, and shifted FA biohydrogenation pathways, favoring the production of C18:1 t11 and C18:2 c9, t11 beneficial to human health. Meat from white lupin-fed lambs had a higher n-3 PUFA content and a reduced n-6/n-3 ratio, with no detrimental effects on meat oxidative stability or color during storage. These findings suggest that fully replacing soybean meal and 30 % of maize with white lupin seeds could beneficially influence meat lipid quality, though adjustments to diet formulation are necessary to mitigate negative effects on feed intake and growth.