SPRING SUMMER BONUS MAGAZINE 2026

Heat stress is becoming amore prevalent occurrence in layer hen operations due to increasing global temperatures. Birds in general are particularly vulnerable to heat stress because they lack sweat glands and rely on panting and behavioural changes to cool down. When environmental temperatures rise above a layer hen’s thermoneutral zone (roughly 18–25°C), their productivity can drop sharply, egg quality suffers, andmortalities can increase. Heat stress can not only affect the short-termperformance of a layer hen, but can also affect their performance for the rest of their lives. Early recognition and proactivemanagement can protect flock health and maintain egg production. Reducing heat stress and its effect on egg production in layer hens Joshua de Kock - Technical Advisor: Monogastric Understanding heat stress Heat stress is caused by high temperature- humidity index values, which means that the thermal neutral zone of layer hens is dependent not only on temperature, but on humidity as well. When humidity is high, the thermoneutral zone of layer hens decreases, meaning that lower environmental temperatures are required to prevent heat stress. High humidity negatively affects the dissipation of heat from layer hens into the surrounding air. De Heus has a mobile application, CoolCare, that enables farmers to determine if their animals are experiencing heat stress by simply checking the weather in their region or manually inputting temperature and humidity levels. By understanding what environmental conditions might increase the likelihood of layer hens experiencing heat stress, farmers can be proactive in their response in order to prevent heat stress from occurring. While extreme cases of heat stress can increase mortalities and significantly decrease egg production, at less extreme temperatures, the effects are often overlooked. When hens experience heat stress, they will start panting in response. This panting can lead to respiratory alkalosis, which can reduce the amount of calcium and carbonate that is transferred via the bloodstream to the shell gland. This causes a decrease in eggshell strength, which cannot be offset by the addition of additional calcium in the diet. Spring/Summer 2026 BONUS www.agribonus.co.za 16