Incubating turkey eggs is often considered to be more challenging than incubating broiler eggs, yet, in essence, the basic principle of success is the same in both turkey and broiler hatcheries. Continuously monitoring the incubation process is crucial to understand what the embryo inside the egg is experiencing and to ensure incubation success. This article highlights four key points a turkey hatchery should closely monitor to reach excellent hatchability and poult quality.
Key points for turkey egg incubation
There are some differences between turkey and broiler eggs. First, turkey eggs generally take 28 days to incubate compared to the 21 days of broiler incubation. Second, turkey eggs are larger than broiler eggs: While the average egg weight of a broiler egg through production increases from 50 to 70 grams, the average turkey egg weight increases from 79 to 97 grams. Third, most - but not all - broiler breeder flocks worldwide are naturally mated whereas the vast majority of turkey breeder flocks are artificially inseminated. Consequently, fertility tends to be higher in turkey eggs, particularly towards the end of production.
Even though there are species-specific considerations to manage, the starting point always is what the embryo experiences during incubation. A turkey hatchery should closely monitor four key points to understand what the embryo inside the egg is experiencing and to ensure incubation success. The following sections each focus on one of these key points.
1. Incubation temperature
Of all the parameters that determine incubation success, temperature is the most important one; more specifically, the temperature experienced by the embryo inside the egg. Below graph shows the temperature inside a turkey egg, the temperature on the surface of the eggshell and the incubator air temperature approximately 10 mm from the egg (= micro-environmental air) when turkey eggs are incubated at a fixed machine temperature of 37.5°C:
- During the first 11 days of incubation, the internal egg temperature is slightly lower than the micro-environmental air temperature because of evaporative cooling. The embryo is still small, so it produces little metabolic heat.
- However, as the embryo starts to grow larger and larger, it produces more and more metabolic heat. Around mid-incubation, the metabolic heat level exceeds the level of heat loss through evaporative cooling. By the end of incubation, the internal egg temperature exceeds the micro-environmental air temperature by approximately 0.5°C.
- The difference between the internal egg temperature and the macro-environmental air temperature (= temperature measured near the machine sensor and indicated on the incubator controller) is assumed to be even bigger than 0.5°C, depending on the machine layout and the airspeed over the egg. To avoid overheating of the eggs and reduced incubation results, it is therefore important to continuously monitor and control the internal egg temperature, especially during later phases of incubation, because the temperature increases as the embryo grows.
The internal egg temperature is of paramount importance… But how to monitor this parameter? An important finding illustrated by the graph is that the eggshell temperature closely follows the internal temperature. Hence, the eggshell temperature is routinely used in commercial incubation to pragmatically estimate the internal temperature. For both turkey and broiler eggs, the consensus is that the optimum eggshell temperature during incubation is around 37.8°C (100°F). When the eggshell temperature deviates from the optimum, incubation performance is at risk.