On-Farm Egg-Holding Temperatures for Commercial Broiler Breeders

Although there have been great improvements in the breeder house, egg transportation and the hatchery, on-farm hatching egg storage has been largely ignored. The lack of improvement might be traced to a lack of information about the optimum environment to maintain viability of hatching eggs stored at the farm level.

Meeting chick placement needs and ensuring the full utilization of incubation equipment have made hatching egg storage inevitable in the commercial broiler industry. While hatching eggs are stored both on-farm and at the hatchery and egg storage data is available at the hatchery level, little if any research aimed at evaluating on-farm hatching egg storage is available.

Hatching-eggs are commonly held at the farm level for three or four days because hatcheries generally make two egg pickups at each farm per week. Eggs are stored at the hatchery for periods ranging from less than a day to a week or longer so that an adequate numbers of eggs can be set to meet chick demand. Length of egg-storage, hen age, egg-storage temperature, and humidity are all pre-incubation storage conditions that affect both hatchability and economic returns nearly as much as incubation conditions. However, as a general rule, hatchery conditions for egg storage are given much more attention than are on-farm egg storage conditions. The ‘less than ideal’ maintenance of on-farm egg storage rooms often reflects this lack of attention.

Current Situation

The embryo in each fertile egg laid has grown 20,000 to 40,000 cells while in the oviduct and represents an ‘already started’ embryo. Following collection at the broiler breeder farm, hatching-eggs are placed in on-farm coolers to reduce the internal egg temperature, arresting further embryonic development, while maintaining embryo viability. The temperature at which embryonic development is virtually stopped is known as the physiological zero, but there is disagreement as to actual temperature at which this occurs. Repeated research done in our lab has found that temperatures of 75°F or below halts embryo development for up to 96 hours of storage.

While some poultry companies are recommending on-farm egg storage temperatures as low as 63°F, the most commonly implemented an on-farm egg storage temperature is 68°F, regardless of flock age. However, this popular industry recommendation is based on data that were originally generated in 1902 and the genetics of both broiler breeders and their offspring have progressed dramatically since that point in time. Although management practices and equipment continue to evolve around the increasingly improved broiler of today, on-farm egg storage has remained largely unchanged.

As broiler breeder age increases, the hatchability typically decreases. While alterations in egg storage conditions might improve hatchability, altering storage conditions at the hatchery for each specific flock is not practical. However, altering egg storage conditions at the farm level may help to achieve improved embryo viability and hatchability. Furthermore, the changes in physical integrity (e.g. shell thickness, albumen quality and size) of the egg as flock age advances, makes it seem logical to investigate flock age as it relates to egg storage temperature. Therefore, the objective of this study was to determine if on-farm egg-storage temperatures would improve hatchability obtained from commercial broiler breeder flocks in four age groups.

Materials and Methods

Hatching-eggs were obtained from four commercial parent-stock broiler breeder flocks representing four ages (25 to 30, 35 to 40, 45 to 50, or 55 to 60 wk of age). Fourteen hundred forty (1440) eggs were collected from each flock on four occasions. Hatching eggs were collected from each breeder farm on day of lay. Eggs were not placed in the existing on-farm egg cooler. Eggs were transported to an experimental egg storage facility and 288 eggs were randomly assigned to storage chambers set to one of five temperatures (60°F, 65°F, 70°F, 75°F, and 80°F). To ensure conditions were maintained correctly during storage, each chamber was equipped with a data logger, which recorded temperature every minute during the holding period. Two trays of 144 eggs were stored at each temperature for 3 days before being placed directly onto the commercial egg transport truck.

At the hatchery eggs were held at 68ºF prior to normal incubation and hatching procedures. Hatchability was determined for each treatment group. Unhatched eggs from each treatment group were subjected to a complete hatch-residue breakout analysis.

Results

The data in Table 1 indicate that eggs from 25 to 30-week-old flocks stored at 60°F had 2.93% higher hatch of fertiles than did those stored at 70°F. However, no significant differences were observed in hatchability. Clearly additional investigation is warranted here.

Table 3. Hatchability and hatch of fertiles from 25 to 30 week old flocks

Storage Temperature	Hatch of Fertile (%)	Hatchability (%)
60ºF	85.31^a	83.77
65ºF	84.47^ab	83.59
70ºF	82.38^b	81.16
75ºF	84.51^ab	83.25
80ºF	84.53^ab	82.64

^a,b Values within columns with different superscripts are significantly different (P<0.05).

The optimum on-farm egg storage temperature for eggs from 35 to 40-week-old flocks was 70°F (Table 2). These findings support much earlier research that indicated for maximum hatch of fertiles, eggs should be stored at or below 70°F. The hatch of fertile for eggs stored at 70°F was 2.56%, 1.80%, 0.21%, and 3.19 % greater than those for eggs stored at 60°F, 65°F, 75°F and 80°F, respectively. For 35 to 40 week-old flocks, an on-farm egg storage of 70°F was found superior to other temperatures with respect to both hatchability and hatch of fertiles.

Similar results were found in eggs from 45 to 50-week-old broiler breeder flocks (Table 3). For 45 to 50 week old breeder flocks, hatch of fertiles obtained from the 70°F storage temperature was 6.68%, 4.85%, 8.38%, and 7.00% higher than eggs stored at temperatures of 60°F, 65°F, 75°F, and 80°F, respectively. Percent hatchability was also highest when eggs were stored at 70°F.

Hatchability and hatch of fertiles was the highest when eggs from 55 to 60-week-old flocks were stored at 75°F (Table 4). Hatch of fertiles for the eggs held at 75°F was 3.19%, 5.17%, 5.00%, and 4.48% higher than those stored at 60°F, 65°F, 70°F and 80°F, respectively. The requirement of a higher on-farm egg storage temperature for older hens was not an expected result. The initial hypothesis was that hatching eggs from older hens might require cooler storage temperatures in order to maintain the structure and composition of the egg albumen and yolk contents. However, these data suggest that eggs from older hens reach physiological zero at a higher temperature than eggs from younger flocks.

Table 2. Hatchability and hatch of fertiles from 35 to 40 week old flocks

Storage Temperature	Hatch of Fertile (%)	Hatchability (%)
60ºF	87.36^ab	85.94^ab
65ºF	88.12^ab	85.68^ab
70ºF	89.92^a	88.19^a
75ºF	88.71^ab	86.63^ab
80ºF	85.73^c	84.03^b

^a,b,c Values within columns with different superscripts are significantly different (P<0.05).

As previously mentioned, a complete egg breakout analysis was performed on all unhatched eggs. However, no significant differences were found between any of the on-farm egg storage groups. Thus, the improvements in hatch reported previously were the result of ‘across the board’ improvements in embryo livability. However, conditions during the research project exposed all eggs to increased handling and transportation conditions. These unusual conditions likely had an affect on overall hatchability and hatch of fertile for all treatment groups, producing hatch or hatch of fertile values which were lower than would typically be seen under industry conditions.

Although hatchability problems can certainly be traced to poor fertility, when fertility remains high, care for hatching eggs can have a tremendous positive effect on the overall hatchability. Current industry on-farm egg storage recommendations vary from 63°F to 68°F. The data presented here suggest that hatchability of eggs from prime age flocks (36 to 49 weeks) is improved by an on-farm eggs storage temperature of 70°F. In addition, the data suggest that eggs from older flocks (>55 wks) will hatch better when stored in the on-farm storage coolers at 75°F. Apparently, hatching eggs from older hens are less viable and more susceptible to stress and therefore more liable to have increased incidences of early embryo mortality. Additionally, these warmer on-farm storage temperatures did not adversely affect the hatch profile. While there was a slight increase in early hatched chicks from eggs held at warmer temperatures it was not significant. Further research is under way to investigate in greater detail the affects of elevated on-farm egg storage on chick quality.

Table 3. Hatchability and hatch of fertiles from 45 to 50 week old flocks

Storage Temperature	Hatch of Fertile (%)	Hatchability (%)
60ºF	78.13^b	76.91^ab
65ºF	79.96^b	78.21^b
70ºF	84.81^a	83.42^a
75ºF	76.43^c	74.57^c
80ºF	77.81^bc	76.04^bc

^a,b,c Values within columns with different superscripts are significantly different (P<0.05).

Conclusion and Summary

Meeting chick placement needs and ensuring the full utilization of incubation equipment have made hatching egg storage inevitable in the commercial broiler industry. Although hatchability problems can certainly be traced to poor fertility, when fertility remains high, care for hatching eggs can have a tremendous positive effect on the overall hatchability. While alterations in egg storage conditions might improve hatchability, altering storage conditions at the hatchery for each specific flock is not practical. However, altering egg storage conditions at the farm level may help to achieve improved embryo viability and hatchability. Although poultry companies recommending on-farm egg storage temperatures between 63ºF and 68°F, regardless of flock age, previous research has been shown that a temperature of 75°F halted embryo development for up to 96 hours. The data presented here suggest that hatching eggs from young flocks (25 to 30 weeks) should be stored on-farm at 68°F. Eggs from flocks in prime age flocks (35 to 50 weeks) should be stored at 70°F on-farm and eggs from older flocks (>55 weeks) should be stored at 75°F. Research presented here would suggest that higher egg storage temperatures could produce an increase in hatch of between 2 and 5% over cooler on farm egg storage room temperatures.

Table 4. Hatchability and hatch of fertiles from 55 to 60 week old flocks

Storage Temperature	Hatch of Fertile (%)	Hatchability (%)
60ºF	73.33^ab	71.63^ab
65ºF	71.35^b	68.40^b
70ºF	71.52^b	68.40^a
75ºF	76.52^a	73.52^a
80ºF	72.04^b	69.79^ab