The Heat is on: Plan now to avoid Productivity Losses in Dairy Cows
As global temperatures continue to rise, dairy farmers around the world will be watching their herds carefully for warning signs of heat stress. The impact of climate change on livestock production is growing, with dairy cows particularly susceptible because of their high metabolic heat production and limited ability to cool themselves.
The 2023 European State of the Climate report (ESOTC 2023), published this month, confirms long-term warming trends with the three warmest years all occurring since 2020. In 2023 there was a record number of days with ‘very strong heat stress’ across Europe where the temperature feels higher than 46C. In France, for example, even nighttime temperatures reached over 30°C. For dairy cows, this level of heat lowers feed intake, rumination and absorption, which reduces milk intake and decreases immune function.
Dr Marta Aguirre , veterinarian from Omya, says the issues get worse the higher the temperature gets. “Stress is an adaptive response that allows animals to cope with environmental challenges, including changes in temperature. The problem is that at very high temperatures, particularly above 30 degrees, the cows’ adaptation mechanisms fail, so they can’t cool themselves down. This has a significant impact on productivity, with losses of up to €400/cow not unusual.”
Heat stress is becoming a worldwide phenomenon. Even in European countries, where the frequency and temperature of hot days is a relatively new consideration, farmers need to plan for its impact on their dairy herds. Research undertaken in the United Kingdom estimates the economic impact of heat stress at between £13.4m in an average year to £33.8m in extreme years (Fodor et al., 2018)
Dr Aguirre advises farmers to mitigate the impact of heat stress in their herds by first evaluating the risk. “The temperature and humidity index (THI) is a way of working out how stressful environmental conditions are becoming for cattle. Combining the air temperature with the relative humidity gives a score that predicts heat stress, with anything above 80 representing severe heat stress.”
The negative effects of heat stress can cause lasting problems. For example, a reduction in feed intake not only creates a loss of condition in the cow, but will change the composition of rumen microbiota, which will damage the rumen epithelium. The associated reduction in rumination can lead to an increase in ruminal acidosis, which is caused by extended periods at low rumen pH.
“Keeping a healthy rumen will eliminate some of the more damaging effects of heat stress,” explains Dr Aguirre. “OmyaFeed C MgO is a palatable buffer which helps maintain rumen pH even during times of reduced saliva recycling or fiber intake, which happens during heat stress. It’s important when the cow is eating less, to make sure the feed is both palatable and offers good electrolyte and mineral balance. OmyaFeed C MgO contains essential calcium and magnesium which are both quickly absorbed by the animal.”
During periods of heat stress cows often experience a reduction in dry matter intake leading to a drop in milk production. This can be mitigated by feed rations with a high dietary cation-anion balance (DCAD). OmyaFeed C MgO has a DCAD of 504 mEq/100 g DM calculated after Horst and Goff (1997) helping to increase the DCAD of the feed formulation to counteract the negative effects of heat stress.
William Plaut, Sales Manager at Eilyps Group, has been using OmyaFeed C MgO for some time. “The product disintegrates perfectly and makes the ration very homogenous. This makes it possible to prevent acidosis without any ruminal disturbance, and the product’s mineral values are a plus, particularly calcium which is sometimes in short supply. OmyaFeed C MgO is a very good alternative so sodium bicarbonate, with an excellent price to performance ratio.”
Other ways in which farmers can help animals cope with extreme temperatures include providing shade and a continuous supply of fresh, clean water, as well as feeding in the early morning or late evening when temperatures may be lower. “Anything that can be done to reduce heat stress will help both the animal and the farm profitability,” concludes Dr Aguirre. “A reduction in milk production and immune function is a regular consequence of heat stress and will affect the animal’s health, reproductive performance and disease resistance. We recommend combatting heat stress early by managing feed intake and quality. OmyaFeed C MgO is easy to include in the ration and will provide a cost-effective solution for farmers when temperatures soar this summer.”
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