Immunohistochemical localization of IL-1β in udder of rats fed different diets at different reproductive stages. The microphotograph from one rat with the positive primary IL-1β antibody was visualized with DAB reaction. The area positive for IL-1β in mammary tissues of rats fed the SO diet (B) or FO diet (C) at day 0 and 14 of gestation was quantified by Easy Image 3000 software. IL-1β production is presented as the average percentage of the positively stained areas (A). Statistics are shown as means ± SE. Statistics with no common letters differ significantly (P < 0.05).