Dairy Farming
ENERGY DENSITY ESSENTIAL IN DAIRY RATIONS DURING SUMMER MONTHS
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s summer temperatures begin to increase, dairy producers should combine management and feed strategy changes to mitigate production loss due to heat stress. “Heat stress is a plague impacting dairy herds globally during hotter months. Not only is it detrimental to animal welfare, but it also impacts milk production, feed efficiency, overall health and even reproduction,” says Dr Richard Kirkland, ruminant nutritionist for Volac Wilmar Feed Ingredients. “Identification, diet and good management are all essential for combating this issue.” For most cows, heat stress can begin at around 25°C. But more important than the external temperature is the combination of temperature and humidity. “The higher the humidity, the more difficult it is for body heat to naturally dissipate
Dr Richard Kirkland, Global Technical Manager for Volac Wilmar Feed Ingredients
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despite sweating and panting. When humidity is involved, cows can suffer from heat stress at lower temperatures than usual, experiencing heat stress in the low 20s,” says Dr Kirkland. Signs of heat stress According to Dr Mike Hutjens, researcher and professor at the University of Illinois, USA, heat stressed dairy cattle are easy to identify with several clinical symptoms varying in degrees of severity. One of the preliminary signs is a shift in behavior. Overheated cows will spend more of their time budget standing and seeking shade. When insufficient shade is provided for an entire group, this may cause individuals to clump together making it even more difficult to dissipate body heat. Increased breathing is another evident sign of excessive heat. “Typically, anything over 60 breaths per minute is a sign of heat stress,” says Dr Hutjens. “This can easily go as high as 80 or 90 breaths per minute (and) that can lead to panting.” Maintenance requirements of heat-stressed cows can increase by up to 25 percent due to activities such as sweating and panting adds Dr Kirkland. The cost of heat stress Excessive heat has several consequences for a cow beyond obvious discomfort. Many of them are completely
unseen while silently eating away at efficiency and productivity. A major effect of heat stress is reduced dry matter intake, with intakes typically reducing by 20 to 40 percent. “The combination of lower dry matter intakes and increased maintenance requirements will quickly put a cow in an energy deficit,” says Dr Kirkland. “As a result, other functions including fertility and milk production are significantly reduced. According to various studies, conception rates can plummet to 10 percent during the hottest months of the year and milk yield by 35 percent.” With altered intake and shifting maintenance requirements, milk composition also suffers. According to Dr Hutjens, this could be in the form of lower milk fat and protein content. Other lessconsidered consequences include an increase in the risk
July-August 2021
