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Egg Characteristics Which Influence Hatchability
Egg Characteristics Which Influence Hatchability M. W. OLSEN AND S. K. HAYNES
U. S. Department ofAgriculture, Agricultural Research Administration, Bettsville, Maryland (Received for publication August 7, 1948)
MAJOR factor in the cost of production of chicks is the excessive loss of eggs which fail to hatch. It has been estimated that approximately 30 eggs of every hundred placed in commercial incubators fail to hatch. Approximately one half of the eggs which have to be discarded are infertile while the remainder represents eggs in which the embryos for various reasons have died during incubation. It is with this group of eggs, the ones that fail to hatch, that this study is concerned. This investigation was undertaken to determine to what extent, undesirable characteristics found in certain eggs affect hatchability and to obtain information as to the numbers and distribution of such eggs. REVIEW OF LITERATURE Knox and Olsen (1936) studied the effect of tremulous air cells on the hatchability of eggs. They found that eggs 1-7 days old with tremulous air cells gave a hatchability of 56.7 percent .whereas eggs with normal air cells hatched 77.3 percent. In this study, tremulous air cells were produced by jarring the eggs against the palm of the hand, the force being directed against the blunt end of the egg. The value of testing hatching eggs prior to incubation for the purpose of eliminating eggs which would show low hatchability was studied by Byerly and Haynes (1938). Eggs 1 day to 1 week old and eggs 3 weeks old were candled by each of 7 investigators, who were asked to seg-
regate eggs that in their opinion would have low hatchability from those that would hatch well. The eggs were then incubated and data gathered on the hatchability of eggs classified as rejects and those classified as good eggs. The results showed that all 7 investigators were able to segregate 1 day old to 1 week old eggs of lower hatchability from those df higher hatchability. Eggs classified as rejects included those with such undesirable characteristics as mobile yolks, tremulous air cells, blood spots and porous shells. Of the fertile eggs classed as rejects, 53 percent hatched whereas 84 percent of the eggs used as controls hatched. Byerly and Haynes concluded, however, that the ability of the several observers in segregating eggs of low hatchability from those of high hatchability was not sufficient to warrant candling eggs prior to incubation as a standard practice. Leonarz (1945) made a detailed study of the hatchability of eggs with certain undesirable characteristics. This study involved the use of more than 39,000 eggs which were produced by several different farm flocks in Texas. Leonarz found that under the temperature conditions prevailing during the late spring and summer in Texas there was a distinct advantage of candling eggs before incubation. This study showed that by removing eggs with certain undesirable characteristics hatchability of fertile eggs could be increased by 10 percent. Leonarz also found that proper storage temperatures were a major factor
198
Downloaded from http://ps.oxfordjournals.org/ at Serials Section, Dixson Library on June 3, 2015
A
EGG CHARACTERISTICS WHICH INFLUENCE HATCHABILITY
in preserving the hatchability of eggs. Eggs 1-5 days old which had been kept at 55°F. prior to setting gave an average hatchability of 87.4 percent of fertile eggs whereas eggs from outside flocks where no special cooling facilities were provided gave an average hatchability of 83.2 percent. MATERIAL AND METHODS
Eight different types of eggs having
characteristics which might influence hatchability were tested for hatchability during this study. These are listed below along with a brief description of the eggs which composed each group. 1. Cracked eggs. Slightly cracked eggs. These also included eggs with the so-called "nest" or "hair" cracks that can be seen only with the aid of the candler. 2. Eggs with poor shells. Eggs with rough, thin shells as well as eggs having rough or thin areas at either the blunt or pointed end. 3. Misshapen eggs. Elongated eggs, round eggs and eggs out of round. 4. Eggs with large blood spots. Eggs with large blood spots which were easily identified before the candler. Eggs in which the blood had diffused throughout the contents were also included. 5. Eggs with misplaced air cells. Eggs with air cells located in positions other than at the blunt end of the egg. In a few instances the air cells were found at the pointed end but usually they were located on the side. 6. Eggs with loose air cells. Eggs in which the two shell membranes had separated so that the air cell was free to move about when the egg was tilted before the candler. 7. Extra large eggs. Eggs weighing 65 grams or more. Eggs having two yolks were not included in this study. 8. Small eggs. Eggs weighing 45 grams or less. These eggs were normal in every respect with the exception of being small. 9. Controls. Eggs laid by the same flock of hens, of the same age, and receiving identically the same treatment as the above, but free from the characteristics given in groups 1-8 and weighing between 50 and 59 grams. RESULTS AND DISCUSSION
During the course of these studies, 47,950 eggs were candled and examined for the 8 characteristics listed. Of this number, 1,894, or approximately 4 percent of the eggs examined, were found to have one of the undesirable characteristics already mentioned. Data are presented in Table 1 showing the relative frequency of occurrence of eggs with the undesirable traits.
Downloaded from http://ps.oxfordjournals.org/ at Serials Section, Dixson Library on June 3, 2015
Eggs laid by a mass-mated flock of Single-Comb White Leghorn pullets at the Agricultural Research Center, Beltsville, Md., were used for these studies. These eggs were gathered twice daily, placed immediately in a refrigerator at 55°F., and held at that temperature until used in these studies. The eggs laid each day were candled when less than 24 hours old by both authors at which time .each egg was marked to identify the particular characteristic it represented. Only eggs with one type of defect were used. Eggs having two or more undesirable traits were discarded. After candling, the various types of undesirable eggs were placed in wire bottomed trays with representative samples of "normal" eggs and returned to the cooler. Each week, for a period of 52 weeks, groups of eggs classified as defective and eggs serving as controls were placed in the same forced draft incubator at 100°F. These eggs were candled on the 7 th day of incubation at which time infertile eggs and eggs containing dead embryos were removed. Eggs which were removed by candling were then broken and the germinal discs examined for evidence of fertility. On the 18th day of incubation, the eggs containing live embryos were transferred to pedigree baskets and placed in a separate hatcher. All eggs which failed to hatch were broken at the close of incubation, and the embryos classified as to time of death.
199
200
M. W. OLSEN AND S. K. HAYNES
Another point of interest in connection with the data presented in Table 1 is the higher incidence of infertility among all undesirable groups of eggs as compared
with that found in eggs used as controls. The degree of infertility varied among the several types, ranging from 21.3 percent in eggs having large blood spots to 51.6 percent for eggs classified as small and weighing 45 grams or less. Of the total of 1,894 undesirable eggs of all types, 28.3 percent were classified as infertile. This is in contrast to 17.7 percent infertility found among the 3,031 eggs serving as controls. The possibility exists that some of the defective eggs classified as infertile were in reality eggs in which early embryonic deaths had occurred. In cases where embryos died earlier than 24 hours of incubation, it is extremely difficult to identify true infertility by macroscopic examination of the germinal discs. Infection of eggs caused by the entry of bacteria or yeast spores through the shells of cracked eggs, poor shelled eggs and misshappen eggs could have been a factor causing early embryonic deaths. However, since infertility was equally high in groups of defective eggs where shell quality was not involved, one must assume that factors other than infection were responsible for the high incidence of infertility. This is es-
TABLE 1.—Percentage infertility and percentage hatchability of various types of defective eggs Percentage hatch *No. of eggs set
*Percentage of total eggs examined
Infertile eggs
Percentage of eggs ' infertile
Cracked eggs Extra large eggs (65 gr. or more) Small eggs (45 gr. or less) Misshapen eggs Poor shells Loose air cells Misplaced air cells Large blood spots
610 332
1.27 .69
155 113
25.4 34.0
155
.32
80
68 102 47 406 174
.14 .21 .10 .85 .36
All defective eggs Control eggs
1894 3031
3.95
Type of defective eggs
Number • of chicks hatched
Fertile eggs set
Total eggs set
242 155
53.2 70.8
39.7 46.7
51.6
60
80.0
38.7
21 28 13 89 37
30.9 27.5 27.7 21.9 21.3
23 35 11 216 98
48.9 47.3 32.4 68.1 71.5
33.8 34.3 23.4 53.2 56.3
536 537
28.3 17.7
840 2174
61.8 87.2
44.4 71.7
* The first two columns of figures in Table 1 gtve the numbers and percentages of eggs of various types found among 47,950 newly laid White Leghorn eggs.
Downloaded from http://ps.oxfordjournals.org/ at Serials Section, Dixson Library on June 3, 2015
The data presented in Table 1 show that cracked eggs were the most frequent type of defect encountered amounting to 1.27 percent of all eggs examined. Eggs with loose air cells occurred the least frequently and represented only .1 percent of the eggs examined. The percentage infertility and the percentage hatchability of each of the 8 types of eggs having undesirable characteristics are presented in Table 1 together with the percentage infertility and hatchability of the control group of eggs. These data show conclusively that eggs with certain defects are less desirable for hatching purposes than eggs which are free of these defects. Of the 1,358 fertile eggs classified as rejects, 840, or 61.8 percent, hatched whereas 87.2 percent of the 2,494 fertile eggs serving as controls hatched. This represents an average difference of 25.4 percent in hatchability in favor of eggs which were free of these particular characteristics.
EGG CHARACTERISTICS WHICH INFLUENCE HATCHABILITY
SUMMARY A study was conducted in which 47,950 freshly laid eggs were candled to determine whether or not certain egg characteristics affect fertility and hatchability. Of these eggs, 1,894, or about 4 percent, had one of the designated characteristics. The hatchability of fertile eggs showing these characteristics was as follows: small eggs, 80.0 percent; large blood spots, 71.5
percent; extra large eggs, 70.8 percent; misplaced air cells, 68.1 percent; misshapen eggs, 48.9 percent; cracked eggs 53.2 percent; eggs with poor shells, 47.3 percent; and loose air cells, 32.4 percent. The average hatchability of all defective eggs was 61.8 percent of fertile eggs while the average hatchability of the 3,031 control eggs was 87.2 percent of fertile eggs. Infertility in all instances was higher in each of the groups of eggs having undesirable characteristics, averaging 28.8 percent for all types of defective eggs, as compared with 17.7 percent for the controls. REFERENCES
Byerly, T. C, and S. K. Haynes, 1938. Testing eggs prior to incubation. Poultry Sci. 17: 152-154. Knox, C. E., and M. W. Olsen, 1936. The effect of tremulous air cells upon the hatchability of eggs. Poultry Sci. 15: 345-348. Leonarz, H., 1945. The care and selection of hatching eggs. Paper prepared for presentation at Meeting of Texas Baby Chick Association, Dallas, Texas.
Downloaded from http://ps.oxfordjournals.org/ at Serials Section, Dixson Library on June 3, 2015
pecially true of groups where the only undesirable trait was that the eggs were either too large or too small and in cases where eggs contained large blood spots but were otherwise normal. Considering hatchability on the basis of total eggs set, we find that 71.7 percent of the eggs used as controls produced chicks whereas only 44.4 percent of the eggs classified as undesirable hatched. This is a difference of 27.3 percent in hatchability in favor of the eggs which were free of the undesirable characteristics.
201
U. S. Department ofAgriculture, Agricultural Research Administration, Bettsville, Maryland (Received for publication August 7, 1948)
MAJOR factor in the cost of production of chicks is the excessive loss of eggs which fail to hatch. It has been estimated that approximately 30 eggs of every hundred placed in commercial incubators fail to hatch. Approximately one half of the eggs which have to be discarded are infertile while the remainder represents eggs in which the embryos for various reasons have died during incubation. It is with this group of eggs, the ones that fail to hatch, that this study is concerned. This investigation was undertaken to determine to what extent, undesirable characteristics found in certain eggs affect hatchability and to obtain information as to the numbers and distribution of such eggs. REVIEW OF LITERATURE Knox and Olsen (1936) studied the effect of tremulous air cells on the hatchability of eggs. They found that eggs 1-7 days old with tremulous air cells gave a hatchability of 56.7 percent .whereas eggs with normal air cells hatched 77.3 percent. In this study, tremulous air cells were produced by jarring the eggs against the palm of the hand, the force being directed against the blunt end of the egg. The value of testing hatching eggs prior to incubation for the purpose of eliminating eggs which would show low hatchability was studied by Byerly and Haynes (1938). Eggs 1 day to 1 week old and eggs 3 weeks old were candled by each of 7 investigators, who were asked to seg-
regate eggs that in their opinion would have low hatchability from those that would hatch well. The eggs were then incubated and data gathered on the hatchability of eggs classified as rejects and those classified as good eggs. The results showed that all 7 investigators were able to segregate 1 day old to 1 week old eggs of lower hatchability from those df higher hatchability. Eggs classified as rejects included those with such undesirable characteristics as mobile yolks, tremulous air cells, blood spots and porous shells. Of the fertile eggs classed as rejects, 53 percent hatched whereas 84 percent of the eggs used as controls hatched. Byerly and Haynes concluded, however, that the ability of the several observers in segregating eggs of low hatchability from those of high hatchability was not sufficient to warrant candling eggs prior to incubation as a standard practice. Leonarz (1945) made a detailed study of the hatchability of eggs with certain undesirable characteristics. This study involved the use of more than 39,000 eggs which were produced by several different farm flocks in Texas. Leonarz found that under the temperature conditions prevailing during the late spring and summer in Texas there was a distinct advantage of candling eggs before incubation. This study showed that by removing eggs with certain undesirable characteristics hatchability of fertile eggs could be increased by 10 percent. Leonarz also found that proper storage temperatures were a major factor
198
Downloaded from http://ps.oxfordjournals.org/ at Serials Section, Dixson Library on June 3, 2015
A
EGG CHARACTERISTICS WHICH INFLUENCE HATCHABILITY
in preserving the hatchability of eggs. Eggs 1-5 days old which had been kept at 55°F. prior to setting gave an average hatchability of 87.4 percent of fertile eggs whereas eggs from outside flocks where no special cooling facilities were provided gave an average hatchability of 83.2 percent. MATERIAL AND METHODS
Eight different types of eggs having
characteristics which might influence hatchability were tested for hatchability during this study. These are listed below along with a brief description of the eggs which composed each group. 1. Cracked eggs. Slightly cracked eggs. These also included eggs with the so-called "nest" or "hair" cracks that can be seen only with the aid of the candler. 2. Eggs with poor shells. Eggs with rough, thin shells as well as eggs having rough or thin areas at either the blunt or pointed end. 3. Misshapen eggs. Elongated eggs, round eggs and eggs out of round. 4. Eggs with large blood spots. Eggs with large blood spots which were easily identified before the candler. Eggs in which the blood had diffused throughout the contents were also included. 5. Eggs with misplaced air cells. Eggs with air cells located in positions other than at the blunt end of the egg. In a few instances the air cells were found at the pointed end but usually they were located on the side. 6. Eggs with loose air cells. Eggs in which the two shell membranes had separated so that the air cell was free to move about when the egg was tilted before the candler. 7. Extra large eggs. Eggs weighing 65 grams or more. Eggs having two yolks were not included in this study. 8. Small eggs. Eggs weighing 45 grams or less. These eggs were normal in every respect with the exception of being small. 9. Controls. Eggs laid by the same flock of hens, of the same age, and receiving identically the same treatment as the above, but free from the characteristics given in groups 1-8 and weighing between 50 and 59 grams. RESULTS AND DISCUSSION
During the course of these studies, 47,950 eggs were candled and examined for the 8 characteristics listed. Of this number, 1,894, or approximately 4 percent of the eggs examined, were found to have one of the undesirable characteristics already mentioned. Data are presented in Table 1 showing the relative frequency of occurrence of eggs with the undesirable traits.
Downloaded from http://ps.oxfordjournals.org/ at Serials Section, Dixson Library on June 3, 2015
Eggs laid by a mass-mated flock of Single-Comb White Leghorn pullets at the Agricultural Research Center, Beltsville, Md., were used for these studies. These eggs were gathered twice daily, placed immediately in a refrigerator at 55°F., and held at that temperature until used in these studies. The eggs laid each day were candled when less than 24 hours old by both authors at which time .each egg was marked to identify the particular characteristic it represented. Only eggs with one type of defect were used. Eggs having two or more undesirable traits were discarded. After candling, the various types of undesirable eggs were placed in wire bottomed trays with representative samples of "normal" eggs and returned to the cooler. Each week, for a period of 52 weeks, groups of eggs classified as defective and eggs serving as controls were placed in the same forced draft incubator at 100°F. These eggs were candled on the 7 th day of incubation at which time infertile eggs and eggs containing dead embryos were removed. Eggs which were removed by candling were then broken and the germinal discs examined for evidence of fertility. On the 18th day of incubation, the eggs containing live embryos were transferred to pedigree baskets and placed in a separate hatcher. All eggs which failed to hatch were broken at the close of incubation, and the embryos classified as to time of death.
199
200
M. W. OLSEN AND S. K. HAYNES
Another point of interest in connection with the data presented in Table 1 is the higher incidence of infertility among all undesirable groups of eggs as compared
with that found in eggs used as controls. The degree of infertility varied among the several types, ranging from 21.3 percent in eggs having large blood spots to 51.6 percent for eggs classified as small and weighing 45 grams or less. Of the total of 1,894 undesirable eggs of all types, 28.3 percent were classified as infertile. This is in contrast to 17.7 percent infertility found among the 3,031 eggs serving as controls. The possibility exists that some of the defective eggs classified as infertile were in reality eggs in which early embryonic deaths had occurred. In cases where embryos died earlier than 24 hours of incubation, it is extremely difficult to identify true infertility by macroscopic examination of the germinal discs. Infection of eggs caused by the entry of bacteria or yeast spores through the shells of cracked eggs, poor shelled eggs and misshappen eggs could have been a factor causing early embryonic deaths. However, since infertility was equally high in groups of defective eggs where shell quality was not involved, one must assume that factors other than infection were responsible for the high incidence of infertility. This is es-
TABLE 1.—Percentage infertility and percentage hatchability of various types of defective eggs Percentage hatch *No. of eggs set
*Percentage of total eggs examined
Infertile eggs
Percentage of eggs ' infertile
Cracked eggs Extra large eggs (65 gr. or more) Small eggs (45 gr. or less) Misshapen eggs Poor shells Loose air cells Misplaced air cells Large blood spots
610 332
1.27 .69
155 113
25.4 34.0
155
.32
80
68 102 47 406 174
.14 .21 .10 .85 .36
All defective eggs Control eggs
1894 3031
3.95
Type of defective eggs
Number • of chicks hatched
Fertile eggs set
Total eggs set
242 155
53.2 70.8
39.7 46.7
51.6
60
80.0
38.7
21 28 13 89 37
30.9 27.5 27.7 21.9 21.3
23 35 11 216 98
48.9 47.3 32.4 68.1 71.5
33.8 34.3 23.4 53.2 56.3
536 537
28.3 17.7
840 2174
61.8 87.2
44.4 71.7
* The first two columns of figures in Table 1 gtve the numbers and percentages of eggs of various types found among 47,950 newly laid White Leghorn eggs.
Downloaded from http://ps.oxfordjournals.org/ at Serials Section, Dixson Library on June 3, 2015
The data presented in Table 1 show that cracked eggs were the most frequent type of defect encountered amounting to 1.27 percent of all eggs examined. Eggs with loose air cells occurred the least frequently and represented only .1 percent of the eggs examined. The percentage infertility and the percentage hatchability of each of the 8 types of eggs having undesirable characteristics are presented in Table 1 together with the percentage infertility and hatchability of the control group of eggs. These data show conclusively that eggs with certain defects are less desirable for hatching purposes than eggs which are free of these defects. Of the 1,358 fertile eggs classified as rejects, 840, or 61.8 percent, hatched whereas 87.2 percent of the 2,494 fertile eggs serving as controls hatched. This represents an average difference of 25.4 percent in hatchability in favor of eggs which were free of these particular characteristics.
EGG CHARACTERISTICS WHICH INFLUENCE HATCHABILITY
SUMMARY A study was conducted in which 47,950 freshly laid eggs were candled to determine whether or not certain egg characteristics affect fertility and hatchability. Of these eggs, 1,894, or about 4 percent, had one of the designated characteristics. The hatchability of fertile eggs showing these characteristics was as follows: small eggs, 80.0 percent; large blood spots, 71.5
percent; extra large eggs, 70.8 percent; misplaced air cells, 68.1 percent; misshapen eggs, 48.9 percent; cracked eggs 53.2 percent; eggs with poor shells, 47.3 percent; and loose air cells, 32.4 percent. The average hatchability of all defective eggs was 61.8 percent of fertile eggs while the average hatchability of the 3,031 control eggs was 87.2 percent of fertile eggs. Infertility in all instances was higher in each of the groups of eggs having undesirable characteristics, averaging 28.8 percent for all types of defective eggs, as compared with 17.7 percent for the controls. REFERENCES
Byerly, T. C, and S. K. Haynes, 1938. Testing eggs prior to incubation. Poultry Sci. 17: 152-154. Knox, C. E., and M. W. Olsen, 1936. The effect of tremulous air cells upon the hatchability of eggs. Poultry Sci. 15: 345-348. Leonarz, H., 1945. The care and selection of hatching eggs. Paper prepared for presentation at Meeting of Texas Baby Chick Association, Dallas, Texas.
Downloaded from http://ps.oxfordjournals.org/ at Serials Section, Dixson Library on June 3, 2015
pecially true of groups where the only undesirable trait was that the eggs were either too large or too small and in cases where eggs contained large blood spots but were otherwise normal. Considering hatchability on the basis of total eggs set, we find that 71.7 percent of the eggs used as controls produced chicks whereas only 44.4 percent of the eggs classified as undesirable hatched. This is a difference of 27.3 percent in hatchability in favor of the eggs which were free of the undesirable characteristics.
201