instructions how to enable JavaScript in your web browser

HEAT STRESS

yes

Benvenuti in Selko®. Questo sito è disponibile anche in italiano.

Benvenuti in Selko®. Questa pagina è disponibile anche in italiano.

Visita il sito Rifiuta

Bienvenido a Selko®. Este sitio también está disponible en español

Bienvenido a Selko®. Esta página también está disponible en inglés

Visitar la web Cancelar

Vítejte ve společnosti Selko®. Tyto stránky jsou k dispozici také v češtině

Vítejte ve společnosti Selko®. Tato stránka je k dispozici také v angličtině

Navštivte stránky Zrušit

Vítame Vás na Selko®. Táto stránka je k dispozícii aj v slovenskom jazyk.

Vitajte v spoločnosti Selko®. Táto stránka je k dispozícii aj v slovenskom jazyku.

Prejdite na webovú lokalitu Zrušit

Bem-vindo à Selko®. Este site também está disponível em língua portuguesa.

Bem-vindo à Selko®. Esta página também está disponível em português.

Visite o site Cancelar

Raising awareness of heat stress in dairy cattle

Key takeaways

Heat stress in dairy cattle can already occur at 20 C or a Temperature Heat Index (THI) of 62
The negative impact of heat stress on health and milk production is significant
Dairy Heat Load Index (DHLI) takes the temperature at the cow into account and is therefore more suitable for grazed cattle
A warning system based on DHLI but also a parameter based on the presence of heat stress is under development

Please click to accept the cookies for Youtube or you can watch the video on the Youtube channel.

Tom Chamberlain, BVSc, PhD, MRCVS, discussed how we can measure the effects of heat stress on cows living in countries with temperate climates and what can be done to avoid loss in performance.

In moderate climates, heat stress can already occur at 20°C

Heat stress in dairy cows is a common problem, even in moderate climates. Due to global warming, it is a growing problem[104]. Milk production[74], and fertility[67,68] in dairy cattle will be negatively affected by heat stress and the incidence of lameness and mastitis will increase[75,80]. Heat stress can be an important potential cause of systemic immune activation[69], which in term can result in involuntary culling of dairy cows[4].

Figure 2, Temperature Humidity Index calculated on the basis of humidity and temperature. If THI exceeds 72, cows can experience mild heat stress and a reduction of fertility. Above a THI of 78, milk production will be reduced. Above 82, very significant losses in milk production will occur in combination with signs of severe heat stress.

Temperature Humidity Index (THI)

A common way to quantify the risk of heat stress is the Temperature Humidity Index (THI), an index which combined environmental temperature and humidity. Threshold values are often based on studies working with cows that are acclimatized to high environmental temperatures and humidity. In those parts of the world, the risk that cows suffer from heat stress starts to occur at THI level of about 72[107] (see Figure 2). Cows in climate zones in which heat stress occurs regularly will adapt and as a result, threshold values will be much lower, can already show signs of heat stress at a THI of 62[74,78]. The THI is based on environmental temperature and humidity. It does not take into account the level of radiation. Therefore, the THI is suitable to quantify the risk of heat stress in housed dairy cattle but has its limitations in grazing cows that are exposed to direct sunlight.

Figure 3: real-time THI and DHLI data, from a farm in the South of England, taken from the website grazemore.co.uk.

Dairy Heat Load Index (DHLI)

With the support of Trouw Nutrition, Dr. Tom Chamberlain, veterinarian and owner of Chalcombe Consultancy, is running a project “Raising the awareness of heat stress problems with dairy farmers”. The project has a number of important targets. The first one is to increase awareness that heat stress can also affect cattle in temperate climate zones such as North West Europe and the coastal areas of Latin America and North America. Next to that, a target is to monitor the risk for heat stress with a parameter that is more suitable for grazing cattle, the so-called Dairy Heat Load Index (DHLI).

Dr. Chamberlain comments: “In grazing situations it is preferrable to work with the Dairy Heat Load Index, which is based upon recordings of humidity and temperature in a so called “black globe”. This black globe is placed where the cattle are grazing, giving you an accurate measurement of the conditions a cow really has to face. We now have real-time data for THI and DHLI available from seven farms in the South-West of England (See Figure 2). The results are available in real-time through our webpage.”

Towards a metric to diagnose heat stress in dairy cows

The third target of the project is to provide farmers with a better tool to help them with assessing heat stress in their herds. Both THI and DHLI are environment and not animal based. As such, they indicate to what extend animals are at risk, but they do not measure the effect of heat stress in animals. The project will develop a metric based on animal measurements. Dr Chamberlain continues: “Previous research workers have developed animal-based metrics, but these have been too invasive or expensive for commercial use. Our intention is to develop a metric that is simple to apply on commercial dairy farms.”

Questions asked during the webinar...

Question	Answer
What would be the critical heat stress temperature for heat adapted cows that reside in hot climates such as South Africa?	If cows are in hot climates, they adapt to heat more easily. Critical heats stress temperatures would therefore be about 26 °C.
How much does the heat stress contribute to the reduction of milk production in terms of cow milk?	As you have seen in the slides by Dr. Chamberlain the average production of heifers will drop by a THI between 62-72 with approx. 2 L/day, with a THI -79 you will loose 2-4 L/day and over 79 THI over 4 L/day.
Is there a difference in het tolerance of different breeds / animals reared in different conditions? and how to deal / with these differences with regard to recommendations?	There are indeed breed differences, especially the Zebu and Girolando (Gir x Holstein cross) cope more easily with warmer conditions. Of course, these varieties do have production differences with, for example, Holstein, which also plays a role in the extent to which the varieties can tolerate heat.
Is it good to wash the cow to reduce heat stress?	Cows cool down as a result of washing, as long as it does not result in an increase of te relative humidity. Thus, cows should be outdoors or in a well ventialted barn if they are being washed.
A very exciting presentation. In for example natural grazing systems what could be those critical interventions that can reduce heat stress?	In a grazing system it's crucial to have enough shadow places, direct sunlight is the biggest risk factor. Provide shade, aim 4 – 6 m2 shade per cow. Maximize eating time / opportunities in evening. ‘Siesta’ management, give best grazing in evenings and offer enough clean and cool water options near grazing areas.
What do you suggest on a nutritional point of view to reduce heat stress?	With more feeding moments, fresh and cool feed, cows will tolerate the heat more easily. For rumen health, sodium bicarbonate is a buffer and probiotics to support stressed rumen.

Download more research and documentation

You can access all of our documentation about Selko protocols, sustainable dairy farming and latest research insights about Dairy Cow health & fertility.

How we can measure the effect of heat stress in dairy cows

Presentation by Dr. Tom Chamberlain MRCVS during the CRV/Selko Webinar July 28, 2021.
Dr. Chamberlain discussed how we can measure the effects of heat stress on cows living in countries with temperate climates and what can be done to avoid loss in performance.

Download presentation - Heat stress in dairy cows

Or visit our download center for more information:

Go to download center

Thank you for your interest in Selko

We have just sent you an email. Follow the instructions in this email to complete your download. Notice that In some cases, spam filters can block automated emails. If you do not find the email in your inbox, please check your junk email folder.

Have a nice day!

Find out more about health and fertility...

Selko Feed Additives

Making sustainable dairy farming more profitable

Selko IntelliBond

Selko IntelliBond’s increased bioavailability and the positive impact on fibre digestion and gut barrier function support well-being and optimizes lactational performance of dairy cows.A recent trial by Professor Santos at the University of Florida showed improved colostrum production, an increase of ECM production of 1.5 kg per day, an improvement of health and fertility and a reduction of the culling rate in animals fed Selko IntelliBond trace minerals for dairy cows.

Selko IntelliOpt Cr

Selko IntelliOpt Cr is a conveneient blend of Selko IntelliBond hydroxy trace minerals in and organic Selko Optimin trace minerals, combined with chromium propionate. Selko IntelliOpt Cr is the result of intensive research, resulting in a trace mineral blend that improves health and perfomance of cattle herds.

Selko | LactiBute

Adding Selko LactiBute to the ration increases milk production while increasing fat and protein levels at the same time. This results in an increase of Energy Corrected Milk of 0.85-1 kg per head per day.

Selko | Fytera Balance

Adding Selko Fytera Balance to the ration of dairy cows reduces systemic inflammation, resulting in an improvement of lactational performance

Selko | TMR

Selko TMR® is a blend of organic acids that reduces the growth of yeasts, moulds and bacteria such as Enterobacteriaceae like Salmonella. As a result of the reduction in growth of micro-organisms, increases in temperature of the TMR are delayed by at least 6 hours in silages treated with Selko-TMR, resulting in a higher dry matter intake.

Selko | Renergy®

Selko Renergy® is a blend of organic acids that modifies rumen fermentation by increasing propionate production. Propionate is a key source of energy for ruminants and is also the most efficient volatile fatty acid (VFA) produced in the rumen. More energy from propionate in the rumen increases production efficiency.

Selko | NutriCool

Even the best heat stress control programme cannot always fully prevent problems with heat stress in dairy cows. Supplementation with Selko NutriCool can help to avoid a drop in dry matter intake and loss of milk production as a result of heat stress.

Selko TOXO HP-R

Discover the power of Selko TOXO HP-R, a mycotoxin mitigation product. Packed with a potent blend of bentonite, β-glucans, and antioxidants, this solution strengthens gut barrier function, boosts immunity, and reduces the impact of immune activation. Our trials prove it: Selko TOXO HP-R not only increases milk production but also enhances fertility in dairy cows exposed to high Fusarium mycotoxin levels.

Selko TOXO-MX

Selko TOXO-MX is part of our Selko Mycotoxin Risk Management Programme and consists of smectite clays, which have shown to have a high binding capacity for aflatoxin B1. With the bioavailability of aflatoxin B1 reduced, the production of aflatoxin M1 is diminished, meaning lower levels are excreted into the milk.

Selko | AOmix

Addressing oxidative stress in cattle with balanced diets rich in antioxidants like Selko AOmix, ensuring improved growth, immune function, and reproduction by offering optimal digestibility and full cellular delivery.

Benvenuti in Selko®. Questo sito è disponibile anche in italiano.

Benvenuti in Selko®. Questa pagina è disponibile anche in italiano.

Bienvenido a Selko®. Este sitio también está disponible en español

Bienvenido a Selko®. Esta página también está disponible en inglés

Vítejte ve společnosti Selko®. Tyto stránky jsou k dispozici také v češtině

Vítejte ve společnosti Selko®. Tato stránka je k dispozici také v angličtině

Vítame Vás na Selko®. Táto stránka je k dispozícii aj v slovenskom jazyk.

Vitajte v spoločnosti Selko®. Táto stránka je k dispozícii aj v slovenskom jazyku.

Bem-vindo à Selko®. Este site também está disponível em língua portuguesa.

Bem-vindo à Selko®. Esta página também está disponível em português.

Raising awareness of heat stress in dairy cattle

Key takeaways

In moderate climates, heat stress can already occur at 20°C

Temperature Humidity Index (THI)

Dairy Heat Load Index (DHLI)

Towards a metric to diagnose heat stress in dairy cows

Questions asked during the webinar...

Download more research and documentation

You can access all of our documentation about Selko protocols, sustainable dairy farming and latest research insights about Dairy Cow health & fertility.

Thank you for your interest in Selko

Find out more about health and fertility...

Aiming for longevity and profitability with healthy cows

Mechanisms and impacts of inflammatory diseases on reproduction in dairy cows

The impact of trace mineral management on reproductive performance of dairy cows

The impact of trace mineral management on semen quality of bulls

Systemic inflammation as a result of heat stress reduces performance of dairy cows.

Breeding dairy cows that are resistant to heat stress

Raising awareness of heat stress in dairy cattle

Global mycotoxin contamination report 2023: Key findings for ruminants

Challenges in the diagnosis of mycotoxicosis in dairy cows

New Fusarium mycotoxins are emerging in dairy cows

Strategies to manage mycotoxin risk in dairy cows

Mycotoxin exposure of dairy cows: animal health, welfare, and food safety