Artificial incubation provides the basis for the commercial poultry Industry. With the increasing interest in captive propagation of exotic species, artificial incubation is becoming more prevalent in the exotic bird industry as well.
Hatching eggs can be stored under appropriate conditions for a week or more prior to incubation without a loss in hatchability. Most information concerning length of storage comes from precocial species important to the poultry and gamebird industries. Little or no information is available on the storage time of hatching eggs from altricial species common to the cage bird industry.
A preliminary study suggested that the maximum storage time for cockatiel eggs prior to incubation was about 3-4 days, after which hatchability declined to less than 50%. This current study was undertaken to evaluate the storage time of cockatiel eggs under several test conditions.
Materials and Methods
Sixty-five pairs of cockatiels were housed in individual breeding units, one pair per cage. Feed and water were provided ad libitum.
Eggs were collected daily between 1600 and 1700 hours and marked with a felt tip marker to indicate parentage and the date egg was laid. Within 3 hrs of collection, eggs were weighed. All cracked eggs were discarded.
Eggs were fumigated using 1.22 ml formalin (37% formaldehyde) and 0.6 grams potassium pernanganate per cu ft for 20 minutes. After fumigation the eggs were distributed into three treatment groups such that no pair produced significantly more eggs for one group than another.
Treatment 1 eggs were placed small end down on cardboard egg flats. These eggs were not turned during storage. Treatment 2 eggs were turned 450 from the vertical once per day. Treatment 3 eggs were placed small end down on cardboard egg flats, bagged in self—sealing freezer bags, and turned 450 from the vertical once per day.
The three groups were stored at a temperature and relative humidity of 55°F and 60 percent, respectively. Eggs were stored from 0-10 days prior to incubation. There were five separate egg settings.
All eggs were weighed Immediately prior to incubation to determine weight loss during the storage period.
Eggs were incubated in a Jamesway 252 incubator at a temperature of 99.5°F and a humidity of 87.00 wet bulb. The eggs were set in chicken trays modified to accommodate the small cockatiel eggs. Eggs were turned automatically every two hours.
At seven days of incubation the eggs were candled and all infertile and early dead embryos were removed for break out examination. On day fifteen of incubation the eggs were candled and any additional dead embryos were removed and examined. All eggs remaining after the second candling were weighed again to determine weight loss between setting and transfer to a Lyon’s glass top hatching machine. The hatching unit was maintained at a temperature and humidity of 98.5°F and 88-90o wet bulb. Eggs that failed to hatch by the 19th day of incubation were removed and examined. Infertile eggs, age at death, and embryonic abnormalities were recorded.
Results and Discussion
Figure 1 shows the pooled hatchability data of the 5 settings by treatment groups relative to storage time. There are no differences in hatchability between the treatment groups, perhaps reflecting sample size. However, hatchability decreased within treatment groups as storage time increased. Hatchability declined in treatments 1 and 2 after four days of storage. This decline in hatchability continued, ultimately reaching 0 at nine and ten days of storage, respectively.
Hatchability remained high in treatment 3 until after the sixth day of storage and did not decline to 0 as was observed in treatments 1 and 2. This demonstrated that bagging eggs during the storage period can successfully increase the storage time. Storage of the eggs in plastic bags appears to reduce the rate of dehydration and pH change due to CO2 loss from the egg. Hatchability began to decrease when weight loss reached 0.04 grams per egg. Treatment 1 lost 0.04 grams per egg by 4 days of storage, treatment 2 by 5 days, and treatment 3 by 6 days, paralleling their decline in hatchability
Figures 2-5 represent embryonic mortality after 1, 5, 7 and 10 days of preincubation storage. No morphological abnormalities were found among the treatment groups. Embryonic mortality is represented as percent mortality (number dead/number survivors on that day) at a given age (days) of embryonic development.
Figure 2 demonstrates that there were essentially no differences among the treatment groups in the early (days 1-4) and late (days 17-19) mortality peaks. The mid peak (days 7-8) mortality associated with treatment 1 is unexpected and was not observed in the other treatment groups.
Figure 3 demonstrates an Increase in the early embryonic mortality of treatment 1 after 5 days of preincubation storage, which one would expect in eggs subjected to extended preincubation storage periods.
Figure 4 shows an increase in both the early and late mortality periods of treatment groups 1 and 2, resulting in a decline in hatchability. Treatment group 3 had a lower mortality in both periods than treatments 1 and 2. Although this was not statistically significant because of sample sizes, bagging appears to improve viability during storage.
Figure 5 demonstrates the embryonic mortality among the treatment groups after 10 days of preincubation storage. Treatments 1 and 2 demonstrate a high embryonic mortality, resulting in zero percent hatchability. Treatment 3 shows a lower mortality than observed In treatments 1 and 2, resulting in eggs hatching after 10 days of storage.
Hatchability of cockatiel eggs declines after 4 days of preincubation storage. Bagging eggs in self-sealing plastic bags can reduce the loss of viability during the preincubation storage period.
The authors acknowledge the guidance, assistance, and review of this manuscript by U.K. Abbott and C.R. Grau.