New research targeting nutrients for stress mitigation

Originally published in the Milk Producer magazine and authored by Sarah Dean & Victoria Asselstine, Jefo Nutrition Inc. & Essi Evans, E+E Technical Advisory Services

Modern dairy cows face an array of physiological and environmental stressors that can impair performance, health and longevity. From heat stress to the metabolic upheaval of the transition period, these challenges alter nutrient needs, compromise Immunity, and increase inflammation and oxidative stress.

Across these stressors, one theme consistently emerges: targeted nutrient supplementation, particularly with specific vitamins, minerals and rumen-protected nutrients, plays a pivotal role in stabilizing cow physiology when it matters most.

Importantly, these stressors rarely occur in isolation. Dairy cows encounter predictable stress periods, with the transition period, nutritional fluctuations and heat stress, that frequently overlap, compounding physiological strain. Each of these stressors reduces dry matter intake and simultaneously increases nutrient demands, creating a dangerous mismatch between supply and requirement.

For example, during the transition period, cows enter a state of negative energy balance as fetal growth and the onset of lactation outpace dietary energy intake. This triggers extensive fat and protein mobilization, elevating NEFA (non esterified fatty acids) and BHB (β hydroxybutyrate) levels, compromising liver function, and weakening immune capacity. Dysfunctional inflammation and oxidative stress follow, elevating the risk of metabolic disease, mastitis, ketosis and impaired reproduction.

Heat stress presents a different, yet equally severe, challenge. Even at moderate THI (temperature–humidity index) levels (68 and above), cows reduce milk production, shift glucose away from the mammary gland, experience compromised rumen function and increase maintenance energy needs. High-producing cows are especially vulnerable due to greater metabolic heat output. Heat stress also carries long-term effects. Dry cows exposed to it produce less milk in the subsequent lactation and give birth to calves with poorer growth and reproductive performance.

The central role of liver function

The liver faces extreme pressure during both thermal and metabolic stress. As the hub for gluconeogenesis, fat metabolism, detoxification and hormone synthesis, compromised hepatic function amplifies the negative cascade of reduced intake, elevated NEFA and weakened immune response.

During inflammation or heightened metabolic activity, free radical production can exceed antioxidant capacity, particularly in the liver where metabolic and detoxification demands are greatest. This results in cellular damage, impaired immunity and reduced tissue function. The glutathione redox cycle, one of the body’s primary antioxidant defense systems, is especially critical in hepatic tissue and relies heavily on key nutrients, including selenium and vitamins B2, B6 and B9.

Why targeted supplementation matters

Targeted nutrient supplementation, especially rumen-protected B vitamins and certain minerals, helps bridge the gap between increased physiological demand and limited dietary supply during stress.

B vitamins: critical co-factors under stress

1. Enhanced immune function

   Riboflavin (B2) boosts neutrophil production and function, ensuring cows can mount rapid innate immune responses during the high-risk transition phase. Protected vitamin blends (B2, B6, B9, B12 and choline) have been shown to reduce incidence of mastitis, metritis and ketosis.

    

2. Oxidative stress mitigation

   Vitamins B2, B6 and B9 support glutathione recycling, enabling cows to deactivate reactive oxygen species and limit cellular damage. This becomes vital during inflammation, heat stress and rapid fat mobilization.

    

3. Improved energy and liver metabolism

   B vitamins function as coenzymes in glucose synthesis and reduce the risk of fatty liver, especially important when NEFA levels rise or when heat stress shifts energy use away from the mammary gland. Studies show protected B vitamin blends increase dry matter intake, reduce BHB, lower liver fat content and support more stable energy metabolism.

    

4. Reproductive and performance benefits under heat stress

   Supplementation during heat stress increases energy-corrected milk by nearly 4 kg/day compared to biotin alone. Cows supplemented with protected B vitamins also demonstrate improved reproductive performance, including higher conception rates, even in hot climates.

Targeted supplementation as herd health strategy

While good management practices remain essential including: adequate cooling, forage consistency, proper stocking density, nutrition is the lever that ensures cows can physiologically withstand stress. Protected B vitamins and supportive minerals such as selenium act directly on the metabolic and immune bottlenecks that limit performance during stress events.

By bolstering antioxidant capacity, stabilizing energy metabolism and supporting immune cell function, targeted supplementation offers producers a proactive, science-based strategy to minimize losses during unavoidable stress periods. It transforms nutrition from a maintenance input to a cornerstone of herd resilience and productivity.

Dairy cows today operate in demanding biological and environmental conditions. Stress is inevitable, but the consequences do not have to be. Specific vitamins, minerals and rumen-protected nutrients consistently demonstrate their power to stabilize physiology, sharpen immune responses and preserve performance when cows need support most. As research from these three resources confirms, targeted supplementation is no longer a marginal strategy, it is foundational to modern herd health management.