SPRING SUMMER BONUS MAGAZINE 2026

Another contributing factor to weak eggshell strength during periods of heat stress is a lower feed intake. A lower feed intake means that less essential minerals required for eggshell synthesis, such as calcium and phosphorus, are consumed and utilised by the hen. Higher percentages of cracked eggs on a layer farm can thus often be traced back to periods of heat stress. Recognising signs of heat stress When hens are experiencing heat stress, they will pant to evaporate moisture from their respiratory tract; this is often the first noticeable sign. On closer inspection, hens spread or droop their wings to increase exposed skin surface for heat loss, often crouching slightly. This behavioural change is not as effective in hens that are housed under high stocking density, as airflow between the hens is limited. During periods of heat stress, water intake dramatically increases, while appetite falls, leading to reduced nutrient intake. Due to the changes in feed and water intake, the droppings from hens may appear watery. It is important that during times where there are high environmental temperatures, sensors in the house are not only functioning correctly, but that they are also at the level where the hens are housed. Prevention of heat stress is the main goal, not treating hens for heat stress when they first show symptoms. Effect on egg production Heat stress can negatively impact egg production, not just by reducing the number of eggs laid, but also by reducing egg size. Heat stress during critical periods of development, such as the rearing and pre-peak phases, can have a negative effect on egg production for the rest of the hen’s life. Hens that have experienced heat stress during rearing can have delayed egg production, reduced uniformity, low egg weights at the onset of egg production and can cause poor eggshell strength even after the period of heat stress has passed. While egg production decreases as a result of heat stress, the eggs that are produced can be of a smaller size with weak eggshell strength, decreasing the number of marketable eggs farmers can sell. Prevention Prevention of heat stress focuses on housing, ventilation, water access, and management adjustments. It is better to act before extreme heat arrives and negatively affects production. Provide strong air movement (fans, tunnel ventilation, or natural flow) to remove excess heat and moisture from the house. In closed houses, aim for adequate exhaust capacity and consider evaporative cooling systems like foggers, misters, or cooling pads when humidity allows. Avoid adding moisture in already humid conditions. Water consumption increases significantly during periods of high temperatures, and it is therefore important to ensure plenty of clean, cool water (ideally 10–15°C). Water lines and drinkers should be in shaded areas and away from warm surfaces such as the roof of the layer house. Hens should also not have to compete for drinkers, with a maximum of 6 hens per water nipple. Lowering stocking density can reduce the heat buildup and improve airflow around each hen. Where possible, use reflective roofing or Figure 1: Hen panting www.agribonus.co.za Spring/Summer 2026 BONUS 17