Why Incubation is Key to Best Broiler Results

Once eggs are delivered to the hatchery, incubation is the first step to raising a profitable flock. Hatchery managers that create the optimum physical conditions for embryos will produce the highest number of top-quality chicks and ultimately achieve the best broiler results.

The measure of success of any hatchery is the number of top-quality chicks produced, called hatchability. This number is expressed as a percentage of all eggs set for incubation. Hatchability is influenced by many factors at both the breeder farm and the hatchery. 

No matter which type of incubation system or setter machine a hatchery uses, all devices manage the temperature, humidity, ventilation and turning of the eggs, creating the optimal incubation environment. 

Temperature Control

Temperature determines the metabolic rate of the embryo and, hence, its rate of development. Because today’s broilers produce higher embryonic temperatures, the risk of embryos overheating is higher than ever.

  1. Any temperature higher or lower than the machine’s recommendations will lead to faster or slower development and decrease hatchability.
  2. Temperatures should remain constant throughout any type of machine, avoiding any hot or cold pockets.
  3. In single-stage incubation, temperature can be altered as embryos grow, starting at a higher temperature and reducing in stages through transfer. In a multi-stage machine, temperature should remain constant.
  4. Incorrectly balanced, too empty and too full can all have adverse affects on hatchability and chick quality.
  5. What to Measure? Use a thermoscan thermometer to accurately estimate embryo temperatures by scanning eggshells at their equator at 15-16 days of incubation. Temperatures between 100-100.5°F (37.8-38.1°C) are optimum and will lead to a good hatch and good chick quality. 


During incubation, water vapor is lost from the egg through the pores of the shell. For best hatchability, an egg must lose 12 percent of its weight by 18 days of incubation.

  1. Due to differences in shell structure, there will be a variation in moisture loss when all eggs are incubated under the same humidity conditions. This variation does not generally have any significant effect on the hatchability.
  2. However, when age, nutrition or disease reduces the eggs’ quality, it may be necessary to adjust incubator humidity conditions to maintain optimum hatchability and chick quality.


Setters draw fresh air from the rooms they are in, supplying oxygen and moisture to maintain the correct relative humidity (RH) levels. The air entering the machines is pre-humidified to closely match the internal RH. The temperature of this air should be 76-80°F (24-27°C). Air leaving the setter removes carbon dioxide and excess heat produced by the eggs. 


Eggs must be turned during incubation to prevent the embryo from sticking to shell membranes, particularly during the first week of incubation and to aid development of the embryonic membranes. As embryos develop and their heat production increases, regular turning will aid airflow and assist cooling. 

Remember, optimum hatchability and chick quality can only be achieved when the egg is held under optimum conditions. Once the egg is laid, its hatching potential can at best be maintained, not improved. For more information, download our guide on Hatchery Management.

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