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Every day the customer demands more quality in the chicks that the hatchery delivers to his farm. Quality is measured in low mortality and good weight gain in the first days. Below we will describe 5 operations that will contribute to improving the quality of your chicks.
1.- Uniform preheating
This management seeks that the eggs that are in the cold room at 15-16 ° C achieve a temperature above the physiological zero (20-25 ° C) in the most homogeneous way possible before the incubation profile starts. The time to reach 25 ° C varies depending on the age of the breeders and the breed. Inside the single-stage incubator it is around 5 to 6 hours and in the corridor 12 hours. Check it!! Every hatchery is different !!
What is the purpose of preheating?
To synchronise the hatch time of all the eggs placed inside the incubators and not have hatched chicks waiting for the slower ones inside the hatchers, causing them to get dehydrated and decreasing the uniformity of the flock upon arrival at the farm. In multistage machines, this handling helps the loaded eggs to not drastically reduce the temperature of the ones already inside and reduces the possibility of eggs sweating, however it has the negative consequence of bacterial contamination –Photo 1–
Single-stage incubators
Single-stage incubators are ideal for preheating since due to their ventilation, the heat is distributed evenly within the machine and prevents eggs from sweating. In the case of multi-stage, it can be done in a nearby room, making sure that all the egg trolleys are exposed to the same temperature or in the corridor in front of the machines. It should be noted that some researchers recommend that eggs from older birds be preheated to lower temperatures for a longer period of time.
Meijerhof et al –1994– reported that 58-week-old breeder eggs pre-heated 16 hours at 20 ° C had a larger hatching than pre-heated 16 hours at 27 ° C (89% Vs 85.1%). 
2.- Correct embryonic temperature
Temperature is a crucial factor for the quality of our chicks. Most genetic companies and hatchery manufacturers recommend embryonic temperatures close to 100 ° F (37.78 ° C). 
It should be noted that studies carried out at much lower temperatures (36.7 ºC = 98.06 ° F) in recent days have reported better yolk-free muscle mass and a higher proportion of heart weight with respect to the body –Maatjens et al 2014–. Embryonic temperatures above 100 ° F (37.78 ºC) generate up to 5% more second-grade or to-be-culled birds–Lourens et al 2005–, due to problems with legs and unhealed navels (black buttons); and with less body mass free of yolk sac. They are birds with good weight but with a percentage of unused yolk sac that is often greater than 20% of the total weight of the chick (ideal is less than 10%). In other words, due to the high temperature, the embryo that was growing stopped using the nutrients of the yolk and used muscular glycogen –Maatjes et al 2014; Leksrisompong et al 2007–.
Additionally, the high temperature reduces the incubation time and therefore the opportunity to use available nutrients in the yolk, especially proteins –Molenaar et al 2010–. Photo 5 shows a very large yolk sac from a bird exposed to high temperatures, particularly in the last week of incubation.
In Photo 6 ,a chick just taken from a hatcher (moisture in neck feathers) with a small yolk sac as a result of good body mass.
Lourens et al 2005 and Joseph et al 2006 reported that chickens incubated at high temperatures (38.9-39.5 ° C) between 7 and 21 days, reached up to 13% less weight per week of age.
3.-Adequate humidity
During the incubation process the eggs must lose weight (water) so that an adequate air chamber is formed to facilitate the hatching of the birds. The maximum hatch is reached when the weight loss is between 12 and 14% at the transfer –Ar and Rahn 1980–.
- Very low humidity during incubation
Hatch is brought forward perhaps because the air would have less capacity to move heat and thus the temperature of the embryo would be higher. When hatching before the scheduled time, the birds would lose weight during their wait.
- High humidity
If the humidity is high, the formation of the air chamber will not be adequate, making it difficult for the birds to free themselves from the shell –Photo 7–, many will get tired and get trapped, and others after exertion will come out but many times injuring their elbows –red elbows -. 
- Very high humidity
If the humidity in the hatchers is very high after the birds hatch, the percentage of birds discarded due to umbilical “threads” will increase –Photo 8– 
4.-Correct temperature
After the chicks are sexed and vaccinated, they are housed in a waiting room to be loaded onto trucks for shipment to the farms. The waiting room should provide the ideal ambient conditions for the birds to find their comfort zone without making unnecessary metabolic costs. You should remember that chicks, the first 4-5 days after hatching, do not fully regulate their temperature and depend on the ambient temperature that surrounds them.
- The ambient temperature of the waiting room fluctuates between 24-28 ° C depending on the speed of the air generated by the fans.
- The best way to know what the correct temperature should be is to check the birds’ cloacal temperature, which should be 103-105 ° F (39.44 – 40.56 ºC).
- Carbon dioxide in the waiting room should be around 2000 ppm.
5.-Management
At the time of hatching, the chicks have some not fully developed physiological systems, including the digestive, immune and thermoregulatory systems.
During the incubation process the nutrients of the chick in formation come from the yolk – being mostly lipids- and the albumen. .
- Several studies have reported that birds that have immediate access to food achieve a higher slaughter weight than birds that did not have food the first 48 hours.
- More importantly, the proportion of breast becomes up to 10% higher in birds that were not subjected to a wait to access feed –Noy and Sklan 1998–
- In addition to the development of the intestinal system, early feed intake makes absorption of the yolk sac faster due to increased intestinal peristalsis –Vieira, 1999–.
- This absorption of the yolk sac is very important since the immunoglobulins that will protect the birds the first days are stored there –Dibner et al 1998–.
- Birds that eat feed early have a better developed Bursa of Fabricius up to 21 days than those that did not have immediate access to feed. This is believed to be due to the production of glucocorticoids during the fasting of birds.
- Glucocorticoids compromise the humoral and cellular immune response in various ways including synthesis of cytokines, interferon, proliferation of T cells, and induces cells to apoptosis etc.
- Additionally, the early presence of biliary IgA and germinal centers –secondary lymphoid organs– was reported in birds that have immediate access to feed. This immunoglobulin is part of the mucosal immune system and its presence shows that the humoral system is well developed.
- Germ centers are organized concentrations of T, B lymphocytes and antigen presenting cells required for vaccine responses –Schat and Myers 1991–.
- The postponement of the access of the birds to feed causes the important immunoglobulins to be used as an energy source –Dibner et al 1998–, making the birds more susceptible to diseases.
- Maternal immunoglobulins make up to 20% of all protein in the yolk sac at birth