Nutritional strategies key to mitigating impacts of heat stress

Multi-generational heat stress impacts can influence future profitability

The impact of heat stress on dairy cows is multi-generational, and how those impacts are mitigated, across all groups within the herd, can dictate current and future milk production and lifetime performance, producers are being advised.

With latest evidence from the United States revealing heat stress can have significant negative impacts on dry cows and in-utero calves, as well as lactating cows, producers must look to mitigate impacts across all groups within the herd.

“We know that all cows suffer from heat stress, but if you are heat stressing the in-utero calf in the dry cow, that has significant implications for that calf’s future productivity,” says KW Feeds technical manager, Dr Anna Sutcliffe.

Production capabilities

Data from a 2020 US study in Florida (Laporta et al, 2020), comparing milk yields from daughters born to dams that were heat stressed, against heifers born to dams that were cooled, recorded significant changes to milk production capabilities.

The heifer off-spring of those cooled cows recorded around 2kg per day higher milk yield, against the daughters of the heat-stressed dams at both first and second lactation, while there was a huge jump of 6.5kg per day, at the third lactation.

“While this study was in Florida, we are seeing more prevalent heat stress challenges in the UK, particularly as we experience increasingly frequent heatwaves and periods of high humidity,” says Dr Sutcliffe.

Mitigation strategies

Heat stress can be mitigated with good management practices for dry cows, with improved ventilation, such as fans and open sides, by reducing stocking density, alongside providing plentiful access to clean, fresh water.

When looking at the milking herd, it is also important to consider that those higher producing cows will most likely have a heat stress impact at lower Temperature Humidity Index (THI), particularly when in their cubicles, so this should be carefully observed.

As well as monitoring THI and following good management practices, Dr Sutcliffe says it is important to consider nutritional strategies, in particular adjusting diets and adding buffers to help stabilise rumen pH.

Supporting DMI

“One of the major impacts of heat stress is to reduce dry matter intake, meaning rumination time drops, and so the cow’s ability to buffer her rumen is compromised. Therefore, the likelihood of suffering from sub-acute rumen acidosis (SARA) is increased,” she says.

“In fact, SARA is just as likely to occur when grazing high quality grass as when feeding energy-dense winter rations. The use of a long-action, highly effective buffering agent such as AcidBuf is therefore beneficial throughout the summer,” she adds.

As well as supporting DMI and helping to increase milk production, by stabilising the rumen pH and providing a source of available calcium, AcidBuf supports gut integrity, reducing the release of endotoxins that can lead to inflammation. This immune response partitions energy and protein away from milk production, compromising milk yield and fertility.

There are also key benefits of feeding the essential oil Xtract, with the inclusion of capsicum in Xtract in particular stimulating the cows to get up to feed and drink, helping to maintain and support intakes.

Live yeasts such as Vistacell also help to stabilise rumen pH and support more consistent rumination behaviour, while Dr Sutcliffe also says the inclusion of the osmolyte-rich feed additive Betaine, can help maintain cell water balance in heat stress conditions.

Betaine helps the cells, both in the rumen and the cow, to maintain water balance and their functionality in those stress conditions,” she explains. “By preventing that cell dehydration, we can help the cow cope with heat stress conditions.”

Combination rumen buffer

KW Chillibuf from KW Feeds is a combination rumen buffer incorporating all of these components, acting to maintain an optimum rumen pH, promoting feed intakes, while improving cell hydration to enable improved performance in heat stress conditions.

“With milk contracts currently offering good returns on increased yields, managing heat stress can minimise any dips in milk production,” says Dr Sutcliffe.

“KW Chillibuf can play an important role in mitigating the negative impacts of heat stress, as part of  a careful nutritional strategy, crucial to supporting cow health, performance and productivity,” she concludes.

Take a look at AcidBuf or KW ChilliBuf to see how they can help with heat stress symptoms!