Dairy Program Heat Stress


Heat stress is defined as an increase of core body temperature above its normal range due to increased total heat load, exceeding the capacity for heat dissipation. Heat stress modifies feed intake, cow behaviour, maintenance requirements, and metabolic processes. This has tremendous consequences for feed efficiency, milk yields, reproductive efficiency, and disease incidence.

The combination of ambient temperature and humidity (THI) determines the level of heat stress.


Heat-stressed animals reduce their feed intake. This is presumably a survival strategy, especially in ruminants, as digesting and processing nutrients generates heat (i.e. thermic effects of feeding). It has traditionally been assumed that inadequate feed intake caused by the thermal load is responsible for decreased milk production (Fuquay, 1981; DeShazer et al., 2009).

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Improving rumen function with yeast probiotic Actisaf® Sc 47

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Studies have demonstrated that feed supplementation with Actisaf® Sc 47 enables rumen redox potential to be reduced. This leads to better fibre digestion, as well as increased anaerobic bacterial activity and lactate-utilising bacteria. These benefits have been achieved under challenging heat stress conditions.


Adding Actisaf® Sc 47 to the feed of heat-stressed cows reduced negative impacts through increasing dry matter intake and milk yields, and improving feed conversion rates.

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Actisaf® Sc 47 restores positive energy balance

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Adding Actisaf® to the diet of heat-stressed cows also changes some important blood parameters, like glucose which has a direct impact on cows’ physiology and metabolism.

Producing more milk and solids

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Actisaf® Sc 47 has been shown to improve milk yield by 1.3 kg or 5.12%. Increased daily fat and protein production has also been reported, confirming that Actisaf® enhances both milk yield and solids under heat stress conditions.

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dairy stress heat

By stabilising the rumen environment and supporting microflora activity, Actisaf® improves rumen function, leading to improved metabolism.

Improved metabolism and heat stress adaptation in dairy cows leads to greater comfort (higher DMI, lower respiratory rate) and higher production (milk quantity and quality).


Higher feed intake, better feed conversion, improved rumen function, and lower respiratory rates, indicate that dairy cows are more comfortable when receiving a live yeast supplement. This leads to increased health and productivity.

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