Yeast extract could be used as a partial substitute for spray-dried porcine plasma in diets for weaned pigs

•Weaning diets supplemented with yeast extract (YE) and spray-dried porcine plasma (SDPP) could improve growth performance (ADG, feed efficiency and ATTD of CP) of piglets compared with control diet.•YE as a partial replacement of SDPP in diet could stimulate the immune responses by improving IgG and IgM content and decreasing TNF-α and IL-6 concentration in serum.•Yeast extract could be a partial substitute for spray-dried porcine plasma in diets for weaned pigs in terms of positive growth performance and immune function.