ARTICLE FEED & ADDITIVE MAGAZINE December 2024 81 timize milk production to ensure producers’ profitability, cow health, longevity and welfare, and the environment while offering consumers high-quality and safe dairy products. The supplementation of live yeast is on the top list of additives to ensure a smooth transition period in dairy cows. WHY DO COWS EXPERIENCE INFLAMMATION, EXCESSIVE LIPID MOBILIZATION AND OXIDATIVE STRESS AROUND CALVING? Inflammation during the transition period is associated with the stress and changes that occur in the cow's body as it prepares for parturition. What is also observed during the transition period is increased metabolic demand due to changes in nutrient intake and metabolism, often leading to a negative energy balance (NEB) and metabolic stress. Metabolic stress is characterized by excessive lipid mobilization, immune and inflammatory dysfunction, and oxidative stress. This period is the largest swing of metabolic status of a dairy cow in a short period of time. These three processes are intrinsically linked (Figure 2) and result in immune and metabolic disorders associated with an increased risk of metabolic and infectious diseases. In addition, the elevated NEFA and beta-hydroxybutyrate (BHB) concentrations from excessive lipid mobilisation and hypoglycaemia, as glucose is required for immune cell function, are important contributors to the periparturient imFigure 1. Simplified representation of LPS/pathogens passages due to leaky gut. LPS = lipopolysaccharide. Figure 2. Schematic representation of the intrinsic relationships among the components of the metabolic stress triad. NF-B=nuclear factor kappa-B; NEFA = Non esterified fatty acids, OS= Oxidative stress, ROS = Reactive oxigen species, TNF = Tumor necrosis factor alpha (Abuelo et al., 2019).
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