Challenges in Maintaining the Hatch Window

Challenges in Maintaining the Hatch Window

Through genetic evolution, broiler chickens reduce their field-rearing time, reaching slaughter weight sooner.

• In mid-2010, chickens reached a weight of 2.5 kg at 42 days.
• Meanwhile, in 2020, chickens reach the same weight at 36 days.

However, the embryonic development time has not changed, taking 21 days to develop and hatch, although the percentage of their life spent in the hatchery has increased due to improved efficiency in the field (Graph 1).

Graph 1. Participation of incubation in the life of a 2.5 kg chicken. Source: COBB

Hatch window

One of the key points for the quality of the chick is the hatch window which is the interval between the first and last chick born.

• However, in practice, it is very difficult to know this precise interval of birth.
• In a more didactic and practical way, the hatching window is calculated based on the percentage of chicks hatched x hours of incubation, thus establishing a curve of chicks hatched.

Hatcheries strive for excellence in chick quality, which can be greatly affected during the hatching window itself. Added to this is the time spent handling the chicks (sexing, vaccination, shipping, and transport), which can subject them to fasting for up to 72 hours until they arrive at the producer’s housing facility.

• This long time from hatching to placement can cause dehydration, impaired yolk sac absorption, and damage to intestinal development that weakens the chicks. This can increase mortality in the first week of life and lead to decreased weight at seven days.

The wider the hatching window, the longer the fasting period for the first chicks to hatch, and together we will have chicks that are too bloated, as they were born very close to the withdrawal and did not have the necessary time to lose the moisture needed after birth.

Figure 1 represents:

• A more uniform hatching window (blue line), shorter hatching time between the first and last chicks, with a large concentration of chicks hatching at the same time.
• A more open hatching window (yellow line) shows a large time difference between the first and last chicks hatched and there is no concentration of chicks hatching in the same interval.

Figure 1.

To ensure a suitable hatching window, care begins even before incubation:

• Egg quality and uniformity.
• Egg storage management.
• Incubation management, with correct loading into incubators.
• Proper management of embryonic development.

These four management points are very important for chick quality and, in addition to being fundamental in controlling the hatching window, they correlate with the total incubation time of the chicks.

DIFFERENCE BETWEEN HATCH WINDOW AND INCUBATION TIME

A very important point is differentiate the hatching window time from the total incubation time for removing the chicks from the hatchers.

• The total hours of hatching or removal of chicks from the hatcher are counted from the time of incubation until the removal of the ready chicks and these hours will vary according to each hatchery, which can be 504 to 516 hours.
• At the end of these hours the chick is removed from the hatcher and processed to be sent to the farm.

In Table 1 below we have some indicators that can influence the hatching window and/or chick collection time.

Table 1. Indicators that can influence the hatch window

1. Incubation too early or too late

When we talk about incubation we must take into account the total number of hours incubated, which refers to the time from the start of incubation until the chicks are removed from the hatcher.

• This indicator is closely related to incubation hours, as different strains have different incubation schedules and egg storage days also interfere with incubation hours.

Examples: When we have storage of 6 or more days, there tends to be an increase in the incubation time of 0.5 to 1 hour per day of additional storage, since we have slower embryos that need more incubation hours the longer they are stored.

Another factor that interferes with incubation hours is the seasons of the year.

• In winter, due to low temperatures, eggs reach a temperature of 23ºC faster than in summer, and they tend to have less embryonic cell development.
• In summer we have more embryonic cells and therefore fewer hours of incubation than in winter because the embryo is more developed at the time of incubation.

2. Incorrect incubator and brooder temperatures

The temperature of embryonic development is a very important factor for the quality of the chicks and will interfere with both the window and the time of removal of chicks from the hatchers.

• High temperatures during development accelerate embryo development, causing them to be born earlier.
• We can notice this problem when there is a high rate of pecked eggs in the transfer, between 18 and 19 days of incubation, and chicks can be found born inside the incubator.
• Ideally, there should be no pecked eggs during transfer, or less than 2%.

Graph A shows an example of an incubator with a uniform temperature that is high for embryos at 18 days, with an average temperature of 102ºF (38.9ºC).

Graph A. Temperature at 18 days of embryonic development – temperature higher than ideal 37.8 °C – average – 37.5 °C

In Graph A1: the birth window in this case will be a window in which 80% of the chicks were born between 468 hours and 492 hours (24-hour interval).

• However, most of the chicks were born 32 hours before the brooder’s departure time.
• In this case, we can find chicks already in the early stages of dehydration, lower chick weight gain, and reduced liveliness upon arrival at the farm.

Graph A1. Window design for developing embryos at a higher temperature throughout the incubation period

When there is a development problem at temperatures below 37.8ºC, embryo growth is slower and, when transferred at 19 days, their physiological age will be behind their chronological age.

In Graph B, we can see that the larger blue area shows an average embryo temperature of 37.5 °C, which is uniform throughout the machine.

Graph B. Temperature at 18 days of embryonic development – lower than the ideal temperature of 37.8ºC – with an average of 37.5ºC

In Graph B1, the birth window has the majority of chicks born between 484 and 508 (24-hour interval),

• However, the peak of birth occurred 12 hours before completing the 512 hours of incubation.
• In this case, when the chicks are removed, they will still be quite wet and swollen (with high moisture yield).
• In this case, we have a higher percentage of chicks eliminated in the classification, chicks with low liveliness.

Graph B1. Window model for embryos that were developing at a lower temperature throughout the incubation period

3. No preheating

Preheating is a very important factor in restarting embryonic development. The preheating allows all eggs to be heated evenly and resume uniform embryonic development.

• When preheating is not performed or is only partially performed on the eggs to be incubated, there are consequences for the eggs to be incubated due to temperature inconsistencies between them.
• In multi-stage incubators, eggs without preheating enter the incubator at an average temperature of 21ºC and are placed in the incubator where the other eggs are already at a temperature very close to 37.8ºC.
• These warmer embryos lose temperature to the environment, as an aid to warming the incoming egg load, slowing their development.

4. Storage days of eggs

Managing egg inventory days is very important in the hatchery to prevent mixing between egg production dates and leaving larger stock egg loads in the hatchery, resulting in younger eggs being incubated.

• In the loading operation it is essential to always start from the highest date of laying to the lowest, so that it is taken as maximum 3 production dates within the same incubator.

5. Reproductive age

An important point is to do an incubation load between the same lineage and the same age among the breeders or very close ages.

Example: if you incubate eggs from two farms, it is preferable that the age of the breeders of the incubated eggs is no more than 5 weeks, within the same incubator.

• The quality of the shell is associated with the age of the breeder and as it ages there is an increase in egg weight, lower fertility rate, higher embryonic mortality and consequent drop in hatching.
• This is because older birds produce eggs with thinner shells and larger pore diameters, and a higher yolk-to-white ratio.

These changes in eggshell quality directly interfere with the gaseous moisture exchange between the embryo and the incubator environment, which is an important factor in the incubation process because it directly affects the weight, incubation time, and quality of the chick at hatching.

6. Microclimate inside incubators and hatchers

A very important point is to monitor the temperature of the embryos inside the incubator to check that the temperature is uniform.

• The more uniform the embryonic development temperature, the more uniform the hatching window will be among chicks.

Let’s look at some examples of eggshell temperature graphs for 18-day-old embryos.

Example 1:

In Temperature Graph C, we observe that there is an unevenness in the development temperature of the embryos inside the incubator, which we call a heat island—embryos further back in the incubator are warmer (average red coloration 39.2 °C) and embryos located at the front of the machine are at an average of 38.5 °C.

• This shows us a large heat island that will directly interfere with the hatching window and the quality of the chicks.
• The chicks located at the back will hatch before the chicks located at the front of the incubator.

Graph C. Shell temperature of embryos at 18 days of development inside an incubator

A well-opened window curve trend, ending with a healthy chick beginning the dehydration process. Wet chicks are born later, closer to the time they are removed from the hatcher, as shown in Graph C1.

Graph C1. Hatching window of Graph C with heat islands within the incubator

The hatch window will always be a challenge for all hatcheries, as it involves many variables from the farm to the hatchery.

• We need to understand each variable and how to minimize or synchronize them so that, together, they result in high-quality chicks for the customer, allowing them to demonstrate their full potential.