The information below has been supplied by dairy marketers and other industry organizations. It has not been edited, verified or endorsed by Hoard's Dairyman.

Cows in a well-cooled barn

As the summer heat approaches, the animals in your care will be at risk of suffering from heat stress. Besides the obvious signs such as panting, heat stress can negatively affect the productivity and health of dairy cattle by impacting dry matter intake and delaying reproductive success. Nationally, heat stress results in total economic losses of approximately $1.5 billion per year driven by production and reproductive losses and an increase in morbidity and mortality of lactating cows (Casarotto et al. 2021). The impact of heat stress on lactation can result in an average reduction of 10 lb/d (Ferreira et al. 2016). “Beyond this, heat stress can affect every animal on a dairy including dry cows and heifers born to heat stressed lactating dams,” states Dr. Keith A. Bryan, technical services specialist at Chr. Hansen. Documented evidence shows us that milk production of heat stressed daughters averaged 4.9 lb/d lower than that of cooled daughters during 35 weeks in milk and peak milk was 8.6 pounds lower (Laporta et al. 2020). This deficit continued into the second lactation resulting in a 5.1 lb/d reduction for the heat stressed group. Bryan continues, “Numerous research results highlight the economic advantage of investing in a heat abatement infrastructure for lactating and dry cows and heifers. In conjunction with infrastructure, managers should also implement effective feeding strategies to improve the animal’s ability to mitigate heat stress.”

Probiotics fit into an effective feeding strategy that can be implemented in conjunction with infrastructure to combat the high economic cost of heat stress. Bryan states, “The main benefits of probiotics within the rumen are to remove oxygen and, in doing so, encourage an increase in fibrolytic bacteria and lactic acid utilizers, helping to stabilize pH.” Probiotics improve the production of important volatile fatty acids, like propionate, that can be absorbed through the rumen wall and transported to the liver, where it is converted to glucose. In the lower gastrointestinal tract (GIT) probiotics have the ability to compete with enteric pathogens, increase the digestibility of the feed through effective enzyme production, enhance mucosal immunity, and improve tight junction protein function which help alleviate leaky gut syndrome.

Consequences of a Leaky Gut

Some of the most commonly used probiotic bacteria and yeast are Lactobacilli (also known as lactic acid bacteria), Bacilli (hardy spore forming bacteria with tremendous stability and lower GIT function), and Saccharomyces cerevisiae (live yeast that can support normal rumen function).

According to Bryan, “To help your cattle before, during, and after the hot season, we recommend daily feeding a combination of effective probiotic bacteria and live yeast. Our best product choices are BOVAMINE® Dairy Plus, a combination of four highly selected bacterial strains, Lactobacillus animalis LA-51, Propionibacterium freudenreichii PF-24, Bacillus subtilis CH201, and Bacillus licheniformis CH200 and BIOMATE® YC-20 (a live yeast). This combination helps support the normal integrity and function of the rumen and lower GIT by reducing heat stress-induced leaky gut syndrome; thereby minimizing health and financial losses associated with heat stress”.


Ferreira, F. C., R. S. Gennari, G. E. Dahl, and A. De Vries. 2016. “Economic Feasibility of Cooling Dry Cows across the United States.” J. Dairy Sci. 99:9931–9941.

Laporta, J., F. C. Ferreira, V. Ouellet, B. Dado-Senn, A. K. Almeida, A. De Vries, and G. E. Dahl. 2020. “Late-Gestation Heat Stress Impairs Daughter and Granddaughter Lifetime Performance.” J. Dairy Sci. 103:7555–7568.

Casarotto, L. T., J. Laporta, and G. E. Dahl. 2021. “Financial impacts of late-gestation heat stress on cow and offspring lifetime performance,” UF/IFAS

About Chr. Hansen
Chr. Hansen is a global, differentiated bioscience company that develops natural ingredient solutions for the food, nutritional, pharmaceutical and agricultural industries. At Chr. Hansen we are uniquely positioned to drive positive change through microbial solutions. We have worked for over 145 years to enable sustainable agriculture, better food and healthier living for more people around the world. Our microbial and fermentation technology platforms, including our broad and relevant collection of around 40,000 microbial strains, have game-changing potential. Matching customer needs and global trends we continue to unlock the power of good bacteria to respond to global challenges such as food waste, global health and the overuse of antibiotics and pesticides. As one of the world’s most sustainable companies, we touch the lives of more than 1 billion people every day. Driven by our legacy of innovation and curiosity to pioneer science, our purpose – To grow a better world. Naturally. – is at the heart of everything we do. (