BONUS SPRING SUMMER 2025

Are panting hens impacting your on-farmperformance? Mark Willment - Technical Advisor: Dairy South African summers are welcomed bymany locals and tourists each year for those who seek out the sun, longer days, andwarmer temperatures. When the heat rises though, so do the challenges for our poultry farmers. The previous summer seasonwas no different. In South Africa’s relentless summers, managing heat stress in commercial layer farms can become incredibly challenging, withmajor economic consequences. Even for egg producers along the coast, lower maximum temperaturesmight be observed than inland, but higher humidity levels contribute to heat stress during the summer months. This can profoundly affect the productivity of a flock, and in extreme cases lead to highmortality rates as well. It is particularly important to try andmanage our layer operations to support birds during these warmer periods. With specificmanagement practices, this can be possible. What is heat stress? Poultry function optimally in what is called the thermoneutral zone (TNZ) or comfort zone. This is the range of ambient air temperature, at bird level, within which a bird can maintain its normal body temperature. For chickens, the TNZ is between 18–26°C. To keep the body temperature within the normal limits, a continuous energy exchange takes place between the animal and the environment. Annalise Kotzé – Technical Advisor: Monogastric & Ostriches Heat stress occurs if this heat exchange becomes more difficult due to environmental factors (such as temperature, humidity, and air speed). When heat production by birds and the environment is greater than heat lost, the core body temperature rises. Measuring the rectal temperature can give you an accurate indication of the level of heat stress. An ideal rectal temperature for a chicken is 40,2–40,8°C, and temperatures that are above 41,1°C indicate heat stress. Birds will show behavioural signs in response to heat stress. Recognising heat stress in chickens It is important to keep a close eye on birds before and during warm periods to detect early signs of heat stress. These signs include: • Open-mouthed breathing, shallow panting • Decreased activity • Decreased feed intake • Increased water consumption Spring/Summer 2025 BONUS www.agribonus.co.za 48