Leaky epithelium at the centre of transition cow disorders How metabolic stress, oxidative imbalance, and dietary shifts disrupt the rumen and lower gut barrier. Why focusing on the rumen and lower gut matters during the transition period? Research shows that inflammation during the transition period negatively impacts cow reproductive performance as it decreases ovarian activity. Concluding remarksYeast-based nutritional additives can help maintain epithelial integrity during the transition period; this helps maintain cow health and high performance under such challenging conditions, yielding high economic outcomes. Leaky epitheliums are the central cause of inflammation and immune activation during the transition period; nutritional additives that help mitigate the negative consequences on cow productivity are important during the cow’s transition period.