ISSUE FOCUS 34 FEED & ADDITIVE MAGAZINE July 2023 Heat stress can disrupt average daily gain (ADG) in beef cattle, but new tools are available to help nutritionists and farmers around the world estimate losses — and take steps to regain production. Plus, recent research investigates the specific critical temperature for beef cattle linked to heat stress and mortality. It appears that some breeds need specific management to better cope with such challenges. WHY IS HEAT STRESS SUCH AN ISSUE IN BEEF CATTLE? Cattle live with a heat-producing engine inside their body: their rumen. A rumen generates heat from fermentation. In addition, the ability of cattle to sweat is limited and only about 10% of an average human’s capacity to perspire. The main way cattle regulate their internal temperature is through panting. This is also why observation of respiration rate is an easy way to detect visible signs of heat stress. Other factors can modulate the severity of heat stress such as coat color, hair length and degree of fat covering (Horner, 2015). Beef cattle in the finishing period can experience more severe heat stress because of their fat covering, which acts like insulation. NEW DATA ON CRITICAL TEMPERATURES FOR BEEF CATTLE Comparing different studies conducted in different countries — France and Italy — shows cattle are able to adapt to the normal climate of the region. Interestingly, cattle coming from France were better adapted to lower temperatures than cattle from Italy, which is further South. Researchers from France (Morignat et al., 2015) show that elevated temperatures (every 1° above the thermoneutral zone) increase the risk of mortality between 4.4 and 5.6%. These results were confirmed by other authors. Studies with dairy cattle show that herd size, breed and age have no effect on THI-related mortality (Crescio et al., 2010). The ability to cope with heat is related to the usual thermoneutral temperature of beef cattle but also to the usual climate of the region. As producers are facing more hot periods, they need to find solutions and to mitigate the consequences when the temperatures reach unusual levels. Reducing the heat burden can be accomplished through: barn design, shade provisions, fans to HOW BEEF CATTLE COPE WITH HEAT STRESS Bruno Martin Ruminant Technical Support Lallemand Animal Nutrition
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