Broiler breeder hatching eggs are commonly held in storage facilities at the breeder farm anywhere from one to four days and again at the hatchery until placed in the setters. In the poultry industry, some pre-incubation of hatching eggs following oviposition and during storage is inevitable, yet efforts should be made to reduce this occurrence.
There have been tremendous advances in the equipment available to maintain hen house temperatures, and in the quality of egg transport vehicles and egg storage facilities at the hatchery. With this improved technology, on-farm egg storage facilities have been largely neglected, which has made it extremely difficult for producers to maintain constant egg storage room temperatures at the farm level.
While one purpose of egg storage is to accumulate eggs to meet the demand for chicks and to best utilise hatchery facilities, ultimately the goal is to arrest further embryonic development while maintaining embryo viability. While an egg storage temperature of 20 C (68 F) is the most commonly practiced industry recommendation, the actual on-farm egg storage temperature can range from a low of 15.6 C (60 F) up to 23.9 C (75 F).
The range in egg storage temperature from one farm to the next is often due to different management programmes, while day-to-day fluctuations within the same company are a result of egg storage facilities that are unable to maintain a constant storage temperature. Hatchery egg storage conditions have been evaluated in the past, with recommendations to reduce losses in hatchability. However, research on egg storage at the breeder farm is limited and incomplete. Therefore, the objective of this study was to determine the effects of oscillating and variable on-farm egg storage temperatures on hatchability and embryo viability in commercial broiler breeder flocks.
Egg storage and hatching procedures
Hatching eggs were obtained from the broiler breeder research facility at the University of Arkansas and were placed into two separate egg storage chambers, with all eggs stored at a control temperature of 21.1 C (70 F) for 0 to 24 hours. After the initial 24-hour period, selected groups of eggs were moved to storage chambers set at temperatures of either 18.9 C (66 F), 20 C (68 F), 22.2 C (72 F), or 23.3 C (74 F) respectively, and stored at these temperatures for 24 to 48 hours.
After 48 hours, eggs stored at 18.9 C (66 F) were moved to 23.3 C (74 F), eggs at 23.3 C (74 F) were moved to 18.9 C (66 F), eggs at 20 C (68 F) were moved to 22.2 C (72 F), and eggs at 22.2 C (72 F) were moved to 20 C (68 F) for 48 to 72 hours of storage. One group of eggs remained at 21.1 C (70 F) for the entire 72-hour storage period. After 72 hours of storage, all eggs were returned to 21.1 C (70 F). This design ensured that all eggs in this experiment were held at an average of 21.1 C (70 F) for the entire three-day on-farm egg storage time period. In summary, the hatching eggs from the different temperature treatment groups were subjected to either a 2 or 4 F temperature fluctuation above and below the 21.1 C (70 F) base temperature.
After the storage period, eggs were transported to their original commercial breeder farm where they were placed directly on a commercial hatching egg transport truck and sent to a commercial hatchery for incubation.
Temperature fluctuation reduces hatch rate
Hatching eggs that were subjected to the temperature change from the basal 21.1 C (70 F) temperature group, had nearly a 2% reduction in hatchability compared with the control group (74.48 vs. 76.47% hatch, respectively). Eggs that underwent a 4 F daily temperature change had nearly a 1% loss in hatch as compared to the control group (75.61 vs. 76.47%, respectively). It is interesting to note that greater temperature variation did not necessarily result in a greater loss in hatchability.
However, regardless of whether the temperature variation was 2 or 4 F, hatching eggs that moved from the hen house to 21.1 C (70 F) then increased in temperature for 24 hours, then decreased after 48 hours and returned back to 21.1 C (70 F) experienced a significant drop in hatchability as compared to the control-stored eggs (3.55% and 2.16% loss in hatch, respectively). Hatchability was reduced from 2 to 3.5% in the two groups that were exposed to these oscillating egg storage temperatures.
Eggs in this group experienced multiple changes in temperature from the hen house to the hatchery. From the time of lay, these eggs decreased in temperature to 21.1 C (70 F). The temperature was then raised for 24 hours, then lowered for 24 hours, then raised for 24 hours, lowered as they were moved to the hatchery 19.4 C (67 F) and then raised when moved to the setters (three periods of decreasing temperatures and three of increasing temperatures).
Eggs that were stored at 21.1 C (70 F), then decreased in temperature for 24 hours, then increased after 48 hours and then returned to 21.1 C (70 F) experienced no difference in hatchability and less than 1% loss in hatch of fertile. Eggs in this treatment group basically underwent one change in direction of the temperature from the time they were laid until the eggs reached the commercial hatchery.
The eggs decreased in temperature after lay to 21.1 C (70 F), then the temperature was decreased again for 24 hours, then raised for 24 hours, lowered for 24 hours and decreased again to 19.4 C (67 F) as they were moved to the hatchery, then raised when moved to the setters (two periods of decreasing temperatures and two of increasing temperatures).
The ideal situation
Each time the internal temperature of the egg is elevated to near 23.9 C (75 F), metabolic activity is again initiated and embryo development ensues, only to be slowed again during additional egg cooling. While cooling hatching eggs is necessary, starting and stopping embryo development weakens the embryo and reduces its viability. The ideal situation is for hatching eggs to undergo only two temperature direction changes; one from the hen to the lowest temperature point at the commercial hatchery egg storage facility and the second temperature direction as eggs are moved into setters.
Hatch variation up to 3.5%
It is well known that most hatchability problems are a result of poor fertility. However, when egg production is attained and the flock maintains high levels of fertility, how we care for hatching eggs can have a tremendous effect on overall hatchability.
While current industry recommendations vary from 17.2 C (63 F) to 21.1 C (70 F), data from this research indicates that variations in on-farm egg storage temperatures of as little as 2 F can reduce hatchability by as much as 3.5%. Experience from evaluating current on-farm egg room temperature values indicates that variations in the actual temperature and the set temperatures are great and often exceed the parameters established in this study.
Therefore, regardless of the equipment in the breeder house and the hatchery facilities, hatchability is routinely lost in commercial hatcheries due to neglect of the on-farm egg storage facilities.