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Seasonal Variation in the Fertility, Mortality and Hatchability of Fayomi Eggs in the Subtropics
524
E. S. E. HAFEZ AND G. A. R. KAMAR
Graham, C. E., H. H. Waitkoff and S. W. Hier, 673-683. 1949. The amino acid content of some scleroRouth, J. L., 1942. Nutritional studies on powdered proteins. J. Biol. Chem. 177: S29-532. chicken feathers. J. Nutrition, 24: 399-404. Newell, G. W., and C. A. Elvehjem, 1947. Nutritive Wilder, O. H. M., 1952. New facts uncovered on value of keratins. III. Effect of source, particle animal protein values. Amer. Meat Inst. Founsize, and method of grinding. J. Nutrition, 33: , dation, Circ. No. 5.
E. S. E. HAFEZ AND G. A. R. KAMAR Facility of Agriculture, Cairo University, Egypt (Received for publication August 10, 1954)
D
URING the course of domestication, there has been a tremendous redistribution in the improved breeds of hens throughout the two hemispheres. The tropical and subtropical zones are characterized by certain seasonal climatological changes, namely the big fluctuation in atmospheric temperature and small variation in day length when compared with the temperate zone. The incubation of eggs is the vital link in the reproductive cycle of the fowl. The study of fertility, embryonic mortality and hatchability of eggs are of great academic and economic importance for modern poultry industries. The reproductive potentialities of the eggs are influenced by environmental, genetical, physiological factors of the hen as well as constitutional, physical and chemical factors of the eggs. The Fayomi breed is a dual-purpose breed, originated in the Fayoom Province, Upper Egypt and is well adapted to the subtropical regions. REVIEW OF LITERATURE The major environmental factors which affect the reproductivity of the fowl is the atmospheric temperature (Kamar, 1954). Fertility and hatchability are lowered when the chickens are kept under high (Heywang, 1944) or low (Payne and In-
gram, 1927) environmental temperature. Chickens kept under air temperature of some 64° to 66°F. have a high fertility and hatchability (Heywang, 1944). The effect of breed, strain and crossbreeding on the percentage of fertility and hatchability has been demonstrated by several investigators. Hatchability is determined by a very large number of genes (Byerly, Knox and Jull, 1934) and could be improved by selective breeding (Wilson and Johnson, 1946). There is always a correlation between the variations in the fertility and hatchability of eggs (Hays, 1951). In the present investigation, it was hoped to study the reproductive capacity in the Fayomi eggs as measured by fertility, viability and hatchability. This was studied in relation to seasonal changes in the climate components at this subtropical locality (30°N.). MATERIALS AND METHODS
A Fayomi flock of hens was available at the Animal Breeding Research Farm, Giza, Egypt. The birds were tested against white diarrhea and were treated periodically against worm infestation with phenothiazine. They were running in groups of 20 to 30 in small open yards shaded with trees. The eggs were collected
Downloaded from http://ps.oxfordjournals.org/ at Indiana University Bloomington Libraries on May 9, 2015
Seasonal Variation in the Fertility, Mortality and Hatchability of Fayomi Eggs in the Subtropics
SEASONAL VARIATION IN REPRODUCTION OF FAYOMI TABLE 1.—Examination of eggs.
Criterion
Age of incubated eggs (days)
Symbol
Not fertilized Died at first test Died in second test Died in shell Pipped Emerged Hatched
7 7 14 21 21 21 21
N. F. D+ D++ D+++ H+ H++ H
+++
Spring: March, April and May. Summer: June, July and August. Autumn: September, October and November. RESULTS
1. Fertility: Throughout a detailed study which covered the whole year, minimum fertility was in August while the maximum was in April (Table 2). Low fertility was maintained during July, August and September when the average atmospheric temperature of 24 hours was ranging from 27.4° to 28.3°C. with an average of 27.7°C. The relative humidity during that period ranged from 48% to 58%. High fertility levels were maintained during December, January and April when the atmospheric temperature was ranging from 13.6° to 20.4°C. with an average of 16.0. The relative humidity ranged from 44% to 67% (Figure 1). The average seasonal fertility was 72% in the TABLE 2.—Monthly variations in the type and percentage of fertility and mortality of eggs at different stages of incubation
Months
March April May June July August September October November December January February
No. of eggs set 251 154 125 120 185 123 107 390 640 761 547 544
Fertility
%
1st test (D+)
2nd test
76 95 89 76 76 63 76 81 84 91 93 88
11 4 4 11 6 23 9 13 4 3 4 3
4 4 12 14 3 4 2 6 5 8 11 7
In shell,
Total
(D+++) 23 25 48 40 16 17 16 20 25 18 23 20
38 33 64 65 25 44 27 39 34 29 38 30
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at two-hour intervals and placed in an egg holding room, while the holding period ranged from 1 to 7 days. During the hot summer months the temperature of the holding room was 2 to 6°C. lower than the outdoor temperature while relative humidity was 5 to 15% higher. During the winter months, the temperature as well as the relative humidity in the holding room was almost similar to that outdoors. Only the eggs that weighed over 45 grams were used. Hearson's Patent Champion incubators heated with hot air were used, their capacity being 120 eggs. The incubators operated at a temperature ranging from 101° to 106°F. and a relative humidity of some 55%. The incubated eggs were tested at fixed intervals by an electric candling device. The feeding and management of the experimental birds were kept as uniform as possible throughout the period of investigation. They were fed ad lib. on balanced rations containing fat, vegetable and animal proteins, minerals and vitamins. The rations contained crushed grains (maize, barley and beans), rice polish and bran, mashed with abbatoir blood. Green feeds were also supplied as Egyptian clover in the winter and green maize during the summer. Fifty Fayomi hens were mated with fiye fertile cocks two months before starting the experiment. 3,947 eggs were incubated throughout twelve months 1952/1953. The incubated eggs were examined at 7 and 14 days of incubation to determine fertility (7 days) and viaability (14 days). The eggs were also examined at the end of incubation to determine viability (21 days) and hatchability as shown in Table 1. The four seasons were considered as follows: Winter: December, January and February.
525
526
E. S. E. HAFEZ AND G. A. R. KAMAR
summer and 9 1 % during the winter (Table 4). The average percentage of fertility for the Fayomi breed was 83% when all the months were included. 2. Mortality: The percentage of mortality at the first test reached a minimum during December and February, while the maximum was recorded during August. The proportion of embryos which died at the second test, or died in shell, as well as the percentage of total mortality was low during September and high during June (Table 2). A high total mortality occurred in April, May and June (temp, of 20.4° to 26.4°C. and relative humidity of 41 to 44%). In July, September and December low mortality percentages were recorded. The percentage of embryos that died at the second test was high in winter and low in the autumn months. The percentage of those which failed to emerge as well as the total deaths reached a minimum in the
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FIG. 1. Monthly differences in the percentage of fertility and hatchability of Fayomi eggs in relation to climatic conditions.
winter and a maximum in the spring. The year average of mortality in the first and second test was 8% and 7% (Table 4). Embryonic mortality in shell was 24% while the average total mortality 'throughout the year was 39%. The proportion of deaths at 7 days of incubation expressed as a percentage to the total mortality was at its minimum in September (temp. 27.4 C. and R.H. 58%) and maximum in March (temp. 16.9°C. and R.H. 48%). The proportions of deaths at 14 days of incubation expressed as a percentage to the total mortality was at its minimum in June (temp. 27.4°C. and R.H. 48%) and maximum in April (temp. 20.4°C. and R.H. 44%). The proportion of deaths at 21 days of incubation expressed as a percentage of total mortality was at its minimum in March (temp. 16.9°C. and R.H. 48%) and maximum in September (temp. 27.4°C. and R.H. 58%). 3. Hatchability: The percentage of eggs which pipped, emerged or hatched as expressed to fertile eggs was very low during June. The percentage of hatchability as expressed to fertile or to all eggs set was at its minimum during June. The highest percentages of pipped, emerged or hatched eggs were recorded in March, April or September (or July) respectively. The percentage of hatchability as expressed in terms of fertile eggs and all eggs set was at its maximum during July and December, respectively (Table 3). The percentage of hatchability of all eggs set decreased in June and August when the average atmospheric temperature was 26.4° and 28.3°C. and relative humidity 44 and 52%. Meanwhile, it increased in December and April at a temperature ranging from 16.0° to 20.4°C. and humidity from 44% to 66%. T h e J e ^ P ^ centage of hatchability of fertile eggs in May and June coincided with temperature conditions of 23.9° to 26.4°C. and rel-
SEASONAL VARIATION IN REPRODUCTION OF FAYOMI TABLE 3.—Monthly variations in the type and percentage of hatchability of eggs at different stages of incubation
251 154 125 120 185 123 107 390 640 761 547 544
48 64 46 27 57 35 55 50 55 65 57 61
March April May June July August September October November December January February
T y p es of hatchability (of fertile eggs) % Pipped Emerged Hatched Total (H+) (H++) ( H 4 ^ 12 2 2 1 5 1 1 3 3 4 7 7
4 6 1 1 2 2 4 3 3 2 3 3
46 59 33 33 68 53 68 55 60 65 52 60
62 67 36 35 75 56 73 61 66 71 62 70
ative humidity of 41 and 44%. In July and September it reached the highest percentage at a temperature of 27.5°C. and relative humidity of some 48% (Figure 1). However, there was a low hatohability during May and June followed by small variations but with an increasing trend in the other months. The proportions of pipped and emerged chicks was low during the summer and high during the winter and spring. The percentage of hatched chicks (H+++) was low in spring and high in autumn. Total percentage hatchability of fertile eggs reached a minimum during the spring and a maximum during the winter. Hatchability percentage of all eggs set reached its minimum in summer TABLE 4.—Seasonal variation in the type and percentage of fertility, mortality and hatchability at different stages of incubation Items
Summer
Autumn
Winter
Year average
1,852
3,947
91
83
530
428
1,137
Fertility %
87
72
80
Type of mortality % (of fertile eggs)
No. of eggs set
Spring
8$,
6 7 32
13 7 24
9 4 20
3 9 20
8 7 24
Total
45
44
33
32
39
5 4 46
2 2 51
3 3 61
6 3 59
4 3 54
O £> -.9- V ^
H+++)
S3£*
Total
Hatchability % (of all eggs)
55
55
67
68
61
53
40
53
61
52
and a maximum during winter. The year average of pipped, emerged or hatched chickens were 4%, 3 % and 54% respectively. The hatchability percentage on basis of fertile eggs and all eggs set was 61 and 52, respectively (Table 4). The percentage of pipped chicks was at its minimum in May (temp. 16.9°C. and R.H. 41%) and maximum in August (temp. 28.3°C. and R.H. 52%). The minimum percentage of emerged chicks expressed as total hatchability occurred in September (temp. 27.4°C. and R.H. 58%) and the maximum was in January (temp. 13.6°C. and R.H. 67%). The percentage of properly hatched (H+++) chicks expressed as total hatchability was low in August (temp. 28.3°C. and R.H. 52%) and high in April (temp. 20.4°C. and R.H. 44%). DISCUSSION
Reproduction in birds is controlled by the reproductive efficiency of the animal fecundity) as well as the reproductive capacity of the egg (incubation qualities). The reproductive efficiency is determined by the patterns of egg-laying such as the attainment of sexual maturity, the intensity of laying as measured by Hafez (1954) and the rate of laying (Romanoff and Romanoff, 1949). Full reproductive capacity of the egg during incubation denotes the fertilizability of germ cell, viability during embryonic life, hatchability from the egg shell and viability of young until complete independency from specific care. There has been some controversy in the terminology used for avian physiology of reproduction. The term fertility used in poultry husbandry does not denote the fertilizability of eggs; the former term has a wider application than the latter. Fertility as measured by macroscopical examination after seven days of incubation is only an approximate measure for fertilizability since a good number of eggs
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W
Hatchability %(of all eggs)
No. of
Months
527
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E. S. E. HAFEZ AND G. A. R. KAMAR
The high relative humidity during the period extending from August to February helps the hatched chickens to break the
shell and hatch out. It seems that the preincubating humidity affects hatchability and not the atmospheric temperature. Cooney (1943) has reported that the temperature ranging from 4° to 32°C. during the holding period had no effect on hatchability. However, both low holding temperature (zero to 4°C.) for less than 6 days (Scott, 1933; and Funk, 1934) and high temperature (34° to 38°C.) for not more than 4 days (Funk, 1934; and Talmadge, 1947) do not effect hatchability, but if these periods increase hatchability is reduced. Increasing relative humidity prior to incubation enables .more chickens to hatch (North, 1941; and Cooney, 1943). The beneficial effect of relative humidity on hatchability is more pronounced when hatchability is related to fertile eggs rather than to all eggs set. In general, the percentage of fertility shows less monthly and seasonal differences than mortality and hatchability variations. However, the fertility and hatchability are reduced when chickens are kept under high environmental temperature (Heywang, 1944). The sudden changes in the atmospheric temperature, humidity and pressure accompanied by the hot stormy weather during May and June months in Egypt exerts an effect on the hatching results. The low fertility can be improved by applying the artificial insemination technique during the hot months of the year. When the environmental temperature is high, holding the eggs in cool rooms not more than 7 days is recommended so as to reduce the early embryonic mortality. The climatic conditions are one of the major factors affecting fertility and hatchability, since they vary greatly in the same year and within the different years. Certain modification for holding the eggs before incubation have been reported by Scott (1933), Funk (1934), Cooney
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which are classified as infertile are actually fertilized but died during the very early embryonic life. This could be easily detected microscopically. The low fertility during the hot climatic conditions may be attributed to the deleterious effect of high atmospheric temperature on semen production of cocks. It is possible that there is a period of low semen production in the male corresponding with the period of low egg laying in the female during the summer months. Also the long holding period of eggs during the summer months may cause the high percentage of "infertility" since some of the eggs which are classified as infertile are actually fertile but were subjected to early embryonic death (not detected microscopically). It seems that atmospheric temperature is the limiting factor which affects fertility rather than relative humidity. Heywang (1944) in Arizona (similar climatic conditions as Egypt) concluded that fertility is lowered when atmospheric temperature is high. The large portion of mortality during the last week of incubation is partly due to lack of vigor or to a thick shell. Also a large proportion of the completely developed embryos which cannot emerge from the shell is a result of low relative humidity either during the holding period or in the incubators. The percentage of dead chicks at the seven-day test is related to variation in atmospheric temperature. The fluctuations in the percentage of mortality at 14 days corresponds with the variations in the relative humidity independent from temperature variations. The fluctuations in the percentage of mortality at 21 days corresponds with the variations in the atmospheric temperature independently from relative humidity variations.
SEASONAL VARIATION IN REPRODUCTION or FAYOMI
SUMMARY
3,947 eggs laid in 2 years by Fayomi hens were incubated throughout twelve months. The incubated eggs were examined at 7, 14 and 21 days of incubation to determine fertility, different stages of
mortality and different types of hatchability (pipped, partially emerged or hatched). 1(a) Minimum fertility percentage was reported in August with the maximum in April. (b) The average season fertility during spring, summer, autumn and winter was 87%, 72%, 80% and 9 1 % respectively. 2(a) The percentage of mortality at the 1st test reached a minimum during December and a maximum during August. (b) The percentage of embryos which died at the 2nd test or died in shell as well as percentage of total mortality was low during September and high during June. 3(a) The percentage of pipped, emerged or hatched chicks was low during June, while the highest was during March, April or September, respectively. (b) The percentage of hatchability was at its minimum during June and maximum during July and December. 4(a) The atmospheric temperature had more effect than relative humidity in respect to fertility. (b) Hatchability was affected by relative humidity independently of atmospheric temperature. 5(a) The practical application of this problem has been discussed. (b) A modified hatching season extending from August to December is recommended in relation to egg quality and male fertility in Egypt. REFERENCES Byerly, T. C , C. W. Knox and M. Jull, 1934. Some genetic aspects of hatchability. Poultry Sci. 13: 230-238. Cooney, W. T., 1943. Preincubation humidity varia-
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(1943) and Talmadge (1947). In the subtropics, it is suggested to modify the hatching season so as to coincide with the period extending from August to December. In this respect Hafez and Kamar (1955) have shown that Fayomi chickens hatched during these months show the best growth and egg production and attain sexual maturity very early at a relatively high body weight. It is the turn of poultry breeders to select new strains which would possess certain qualities of shell such as shell thickness and porosity, to facilitate emerging of chicks during hatching under subtropical conditions. Selecting cocks for high semen quality or for fertility during summer months is of no little importance. Examination of cocks used for breeding must be carried out periodically during the hatching season so as to eliminate cocks of temporary infertility. Further work is needed to find out the genetic, nutritional and pathological causes of this early embryonic mortality. Also the percentage of total mortality at the age of 21 days is considerably high during May and June. It is of no little importance to segregate the genetic and environmental factors concerned in this phenomenon. The study of the effects of increasing relative humidity in the storing rooms as well as incubators is of great interest in subtropical regions. These results are attributed to the environmental conditions of the hens rather than holding conditions for eggs. The latter factor could be made mechanically optimum whereas the former could not under practical conditions.
529
530
N. R. GYLES, G. E. DICKERSON, Q. B. KINDER AND H. L. KEMPSTER eggs as influenced by environment and heredity. Connecticut (Storrs) Agr. Exp. Sta. Bull. No. 262. North, M. O., 1941. High altitude incubation of eggs. U. S. Egg Poultry Mag. 47: 158-159, 184. Payne, L. F., and C. Ingram, 1927. The effects of freezing the combs of breeding males. Poultry Sci. 6: 99-107. Romanoff, A. L., and A. J. Romanoff, 1949. The Avian Egg. p. 27, Wiley, New York. Scott, H. M., 1933. The effect of age and holding temperatures on hatchability of turkey and chicken eggs. Poultry Sci. 12: 49-54. Talmadge, D. W., 1947. Effect of the storage temperatures on the hatchability of eggs. M.Sc. Thesis, Univ. of Massachusetts. Wilson, W. 0., and L. E. Johnson, 1946. The inheritance of egg production and hatchability in turkeys. Poultry Sci. 25: 278-284.
Initial and Actual Selection in Poultry 1 N. R. GYLES, 2 G. E. DICKERSON, 3 Q. B. KINDER AND H. L. KEMPSTER Departments of Animal and Poultry Husbandry, University of Missouri, Columbia (Received for publication August 17, 1953)
T
HE general improvement in various aspects of animal performance, over a number of years and in several countries, has been outlined by Lush (1951). Although the portion of such improvement which may be attributed to the selection of superior breeding stock cannot be determined precisely, there is little doubt that much of it is genetic. This interpretation is strengthened by the demonstrated power of selection to develop divergence in the performance of strains derived from the same original stock in rats (Morris et al., 1933), in chickens (Lamoreux et al.,
1 This paper includes results presented by the senior author as a doctoral dissertation. Published with the approval of the Director, Missouri Agricultural Experiment Station. 2 Now Poultry Geneticist, University of Arkansas, Fayetteville, Arkansas. 3 Now Geneticist, Kimber Farms, Inc., Niles, California.
1943), in swine (Krider et al., 1946; and Dickerson and Grimes, 1947), in mice (MacArthur, 1949), and in corn (Woodworth et al., 1952). Some poultry breeders have reported that continued improvement is discouragingly slow in egg production flocks which have achieved a high level of performance as the result of consistent selection over a long period of years. These flocks are reputed to be well managed and to base their selection of breeding stock on performance of individuals, sibs and progeny. A plateau in performance seems to have been reached, although the degree of determination by heredity remains relatively high for most individual traits. Information concerning the possible reasons for such "diminishing returns" from selection may suggest methods for making further progress.
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tions effects on chicken egg hatchability. Oregon Agr. Exp. Sta. Tech. Bull. No. 2. Funk, E. M., 1934. Factors influencing hatchability in the domestic fowl. Missouri Agr. Exp. Sta. Bull. No. 341. Hafez, E. S. E., 1954. Organ development in relation to egg laying capacity in the fowl. J. Agr. Sci. 45:148-155. Hafez, E. S. E., and G. A. R. Kamar, 1955. Sexual maturity and related phenomenon. J. Agr. Sci. 45: (In the Press). Hays, F. A., 1951. Fertility and hatchability in Rhode Island Reds. Poultry Sci. 30: 153. Heywang, B. W., 1944. Fertility and hatchability when the environmental temperature of chickens is high. Poultry Sci. 23: 334-339. Kamar, G. A. R., 1954. Developmental and physiological aspects in the reproduction of domestic fowl. M.Sc. Thesis, Cairo Univ., Egypt. Landauer, W., 1948. The hatchability of chicken
E. S. E. HAFEZ AND G. A. R. KAMAR
Graham, C. E., H. H. Waitkoff and S. W. Hier, 673-683. 1949. The amino acid content of some scleroRouth, J. L., 1942. Nutritional studies on powdered proteins. J. Biol. Chem. 177: S29-532. chicken feathers. J. Nutrition, 24: 399-404. Newell, G. W., and C. A. Elvehjem, 1947. Nutritive Wilder, O. H. M., 1952. New facts uncovered on value of keratins. III. Effect of source, particle animal protein values. Amer. Meat Inst. Founsize, and method of grinding. J. Nutrition, 33: , dation, Circ. No. 5.
E. S. E. HAFEZ AND G. A. R. KAMAR Facility of Agriculture, Cairo University, Egypt (Received for publication August 10, 1954)
D
URING the course of domestication, there has been a tremendous redistribution in the improved breeds of hens throughout the two hemispheres. The tropical and subtropical zones are characterized by certain seasonal climatological changes, namely the big fluctuation in atmospheric temperature and small variation in day length when compared with the temperate zone. The incubation of eggs is the vital link in the reproductive cycle of the fowl. The study of fertility, embryonic mortality and hatchability of eggs are of great academic and economic importance for modern poultry industries. The reproductive potentialities of the eggs are influenced by environmental, genetical, physiological factors of the hen as well as constitutional, physical and chemical factors of the eggs. The Fayomi breed is a dual-purpose breed, originated in the Fayoom Province, Upper Egypt and is well adapted to the subtropical regions. REVIEW OF LITERATURE The major environmental factors which affect the reproductivity of the fowl is the atmospheric temperature (Kamar, 1954). Fertility and hatchability are lowered when the chickens are kept under high (Heywang, 1944) or low (Payne and In-
gram, 1927) environmental temperature. Chickens kept under air temperature of some 64° to 66°F. have a high fertility and hatchability (Heywang, 1944). The effect of breed, strain and crossbreeding on the percentage of fertility and hatchability has been demonstrated by several investigators. Hatchability is determined by a very large number of genes (Byerly, Knox and Jull, 1934) and could be improved by selective breeding (Wilson and Johnson, 1946). There is always a correlation between the variations in the fertility and hatchability of eggs (Hays, 1951). In the present investigation, it was hoped to study the reproductive capacity in the Fayomi eggs as measured by fertility, viability and hatchability. This was studied in relation to seasonal changes in the climate components at this subtropical locality (30°N.). MATERIALS AND METHODS
A Fayomi flock of hens was available at the Animal Breeding Research Farm, Giza, Egypt. The birds were tested against white diarrhea and were treated periodically against worm infestation with phenothiazine. They were running in groups of 20 to 30 in small open yards shaded with trees. The eggs were collected
Downloaded from http://ps.oxfordjournals.org/ at Indiana University Bloomington Libraries on May 9, 2015
Seasonal Variation in the Fertility, Mortality and Hatchability of Fayomi Eggs in the Subtropics
SEASONAL VARIATION IN REPRODUCTION OF FAYOMI TABLE 1.—Examination of eggs.
Criterion
Age of incubated eggs (days)
Symbol
Not fertilized Died at first test Died in second test Died in shell Pipped Emerged Hatched
7 7 14 21 21 21 21
N. F. D+ D++ D+++ H+ H++ H
+++
Spring: March, April and May. Summer: June, July and August. Autumn: September, October and November. RESULTS
1. Fertility: Throughout a detailed study which covered the whole year, minimum fertility was in August while the maximum was in April (Table 2). Low fertility was maintained during July, August and September when the average atmospheric temperature of 24 hours was ranging from 27.4° to 28.3°C. with an average of 27.7°C. The relative humidity during that period ranged from 48% to 58%. High fertility levels were maintained during December, January and April when the atmospheric temperature was ranging from 13.6° to 20.4°C. with an average of 16.0. The relative humidity ranged from 44% to 67% (Figure 1). The average seasonal fertility was 72% in the TABLE 2.—Monthly variations in the type and percentage of fertility and mortality of eggs at different stages of incubation
Months
March April May June July August September October November December January February
No. of eggs set 251 154 125 120 185 123 107 390 640 761 547 544
Fertility
%
1st test (D+)
2nd test
76 95 89 76 76 63 76 81 84 91 93 88
11 4 4 11 6 23 9 13 4 3 4 3
4 4 12 14 3 4 2 6 5 8 11 7
In shell,
Total
(D+++) 23 25 48 40 16 17 16 20 25 18 23 20
38 33 64 65 25 44 27 39 34 29 38 30
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at two-hour intervals and placed in an egg holding room, while the holding period ranged from 1 to 7 days. During the hot summer months the temperature of the holding room was 2 to 6°C. lower than the outdoor temperature while relative humidity was 5 to 15% higher. During the winter months, the temperature as well as the relative humidity in the holding room was almost similar to that outdoors. Only the eggs that weighed over 45 grams were used. Hearson's Patent Champion incubators heated with hot air were used, their capacity being 120 eggs. The incubators operated at a temperature ranging from 101° to 106°F. and a relative humidity of some 55%. The incubated eggs were tested at fixed intervals by an electric candling device. The feeding and management of the experimental birds were kept as uniform as possible throughout the period of investigation. They were fed ad lib. on balanced rations containing fat, vegetable and animal proteins, minerals and vitamins. The rations contained crushed grains (maize, barley and beans), rice polish and bran, mashed with abbatoir blood. Green feeds were also supplied as Egyptian clover in the winter and green maize during the summer. Fifty Fayomi hens were mated with fiye fertile cocks two months before starting the experiment. 3,947 eggs were incubated throughout twelve months 1952/1953. The incubated eggs were examined at 7 and 14 days of incubation to determine fertility (7 days) and viaability (14 days). The eggs were also examined at the end of incubation to determine viability (21 days) and hatchability as shown in Table 1. The four seasons were considered as follows: Winter: December, January and February.
525
526
E. S. E. HAFEZ AND G. A. R. KAMAR
summer and 9 1 % during the winter (Table 4). The average percentage of fertility for the Fayomi breed was 83% when all the months were included. 2. Mortality: The percentage of mortality at the first test reached a minimum during December and February, while the maximum was recorded during August. The proportion of embryos which died at the second test, or died in shell, as well as the percentage of total mortality was low during September and high during June (Table 2). A high total mortality occurred in April, May and June (temp, of 20.4° to 26.4°C. and relative humidity of 41 to 44%). In July, September and December low mortality percentages were recorded. The percentage of embryos that died at the second test was high in winter and low in the autumn months. The percentage of those which failed to emerge as well as the total deaths reached a minimum in the
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FIG. 1. Monthly differences in the percentage of fertility and hatchability of Fayomi eggs in relation to climatic conditions.
winter and a maximum in the spring. The year average of mortality in the first and second test was 8% and 7% (Table 4). Embryonic mortality in shell was 24% while the average total mortality 'throughout the year was 39%. The proportion of deaths at 7 days of incubation expressed as a percentage to the total mortality was at its minimum in September (temp. 27.4 C. and R.H. 58%) and maximum in March (temp. 16.9°C. and R.H. 48%). The proportions of deaths at 14 days of incubation expressed as a percentage to the total mortality was at its minimum in June (temp. 27.4°C. and R.H. 48%) and maximum in April (temp. 20.4°C. and R.H. 44%). The proportion of deaths at 21 days of incubation expressed as a percentage of total mortality was at its minimum in March (temp. 16.9°C. and R.H. 48%) and maximum in September (temp. 27.4°C. and R.H. 58%). 3. Hatchability: The percentage of eggs which pipped, emerged or hatched as expressed to fertile eggs was very low during June. The percentage of hatchability as expressed to fertile or to all eggs set was at its minimum during June. The highest percentages of pipped, emerged or hatched eggs were recorded in March, April or September (or July) respectively. The percentage of hatchability as expressed in terms of fertile eggs and all eggs set was at its maximum during July and December, respectively (Table 3). The percentage of hatchability of all eggs set decreased in June and August when the average atmospheric temperature was 26.4° and 28.3°C. and relative humidity 44 and 52%. Meanwhile, it increased in December and April at a temperature ranging from 16.0° to 20.4°C. and humidity from 44% to 66%. T h e J e ^ P ^ centage of hatchability of fertile eggs in May and June coincided with temperature conditions of 23.9° to 26.4°C. and rel-
SEASONAL VARIATION IN REPRODUCTION OF FAYOMI TABLE 3.—Monthly variations in the type and percentage of hatchability of eggs at different stages of incubation
251 154 125 120 185 123 107 390 640 761 547 544
48 64 46 27 57 35 55 50 55 65 57 61
March April May June July August September October November December January February
T y p es of hatchability (of fertile eggs) % Pipped Emerged Hatched Total (H+) (H++) ( H 4 ^ 12 2 2 1 5 1 1 3 3 4 7 7
4 6 1 1 2 2 4 3 3 2 3 3
46 59 33 33 68 53 68 55 60 65 52 60
62 67 36 35 75 56 73 61 66 71 62 70
ative humidity of 41 and 44%. In July and September it reached the highest percentage at a temperature of 27.5°C. and relative humidity of some 48% (Figure 1). However, there was a low hatohability during May and June followed by small variations but with an increasing trend in the other months. The proportions of pipped and emerged chicks was low during the summer and high during the winter and spring. The percentage of hatched chicks (H+++) was low in spring and high in autumn. Total percentage hatchability of fertile eggs reached a minimum during the spring and a maximum during the winter. Hatchability percentage of all eggs set reached its minimum in summer TABLE 4.—Seasonal variation in the type and percentage of fertility, mortality and hatchability at different stages of incubation Items
Summer
Autumn
Winter
Year average
1,852
3,947
91
83
530
428
1,137
Fertility %
87
72
80
Type of mortality % (of fertile eggs)
No. of eggs set
Spring
8$,
6 7 32
13 7 24
9 4 20
3 9 20
8 7 24
Total
45
44
33
32
39
5 4 46
2 2 51
3 3 61
6 3 59
4 3 54
O £> -.9- V ^
H+++)
S3£*
Total
Hatchability % (of all eggs)
55
55
67
68
61
53
40
53
61
52
and a maximum during winter. The year average of pipped, emerged or hatched chickens were 4%, 3 % and 54% respectively. The hatchability percentage on basis of fertile eggs and all eggs set was 61 and 52, respectively (Table 4). The percentage of pipped chicks was at its minimum in May (temp. 16.9°C. and R.H. 41%) and maximum in August (temp. 28.3°C. and R.H. 52%). The minimum percentage of emerged chicks expressed as total hatchability occurred in September (temp. 27.4°C. and R.H. 58%) and the maximum was in January (temp. 13.6°C. and R.H. 67%). The percentage of properly hatched (H+++) chicks expressed as total hatchability was low in August (temp. 28.3°C. and R.H. 52%) and high in April (temp. 20.4°C. and R.H. 44%). DISCUSSION
Reproduction in birds is controlled by the reproductive efficiency of the animal fecundity) as well as the reproductive capacity of the egg (incubation qualities). The reproductive efficiency is determined by the patterns of egg-laying such as the attainment of sexual maturity, the intensity of laying as measured by Hafez (1954) and the rate of laying (Romanoff and Romanoff, 1949). Full reproductive capacity of the egg during incubation denotes the fertilizability of germ cell, viability during embryonic life, hatchability from the egg shell and viability of young until complete independency from specific care. There has been some controversy in the terminology used for avian physiology of reproduction. The term fertility used in poultry husbandry does not denote the fertilizability of eggs; the former term has a wider application than the latter. Fertility as measured by macroscopical examination after seven days of incubation is only an approximate measure for fertilizability since a good number of eggs
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W
Hatchability %(of all eggs)
No. of
Months
527
528
E. S. E. HAFEZ AND G. A. R. KAMAR
The high relative humidity during the period extending from August to February helps the hatched chickens to break the
shell and hatch out. It seems that the preincubating humidity affects hatchability and not the atmospheric temperature. Cooney (1943) has reported that the temperature ranging from 4° to 32°C. during the holding period had no effect on hatchability. However, both low holding temperature (zero to 4°C.) for less than 6 days (Scott, 1933; and Funk, 1934) and high temperature (34° to 38°C.) for not more than 4 days (Funk, 1934; and Talmadge, 1947) do not effect hatchability, but if these periods increase hatchability is reduced. Increasing relative humidity prior to incubation enables .more chickens to hatch (North, 1941; and Cooney, 1943). The beneficial effect of relative humidity on hatchability is more pronounced when hatchability is related to fertile eggs rather than to all eggs set. In general, the percentage of fertility shows less monthly and seasonal differences than mortality and hatchability variations. However, the fertility and hatchability are reduced when chickens are kept under high environmental temperature (Heywang, 1944). The sudden changes in the atmospheric temperature, humidity and pressure accompanied by the hot stormy weather during May and June months in Egypt exerts an effect on the hatching results. The low fertility can be improved by applying the artificial insemination technique during the hot months of the year. When the environmental temperature is high, holding the eggs in cool rooms not more than 7 days is recommended so as to reduce the early embryonic mortality. The climatic conditions are one of the major factors affecting fertility and hatchability, since they vary greatly in the same year and within the different years. Certain modification for holding the eggs before incubation have been reported by Scott (1933), Funk (1934), Cooney
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which are classified as infertile are actually fertilized but died during the very early embryonic life. This could be easily detected microscopically. The low fertility during the hot climatic conditions may be attributed to the deleterious effect of high atmospheric temperature on semen production of cocks. It is possible that there is a period of low semen production in the male corresponding with the period of low egg laying in the female during the summer months. Also the long holding period of eggs during the summer months may cause the high percentage of "infertility" since some of the eggs which are classified as infertile are actually fertile but were subjected to early embryonic death (not detected microscopically). It seems that atmospheric temperature is the limiting factor which affects fertility rather than relative humidity. Heywang (1944) in Arizona (similar climatic conditions as Egypt) concluded that fertility is lowered when atmospheric temperature is high. The large portion of mortality during the last week of incubation is partly due to lack of vigor or to a thick shell. Also a large proportion of the completely developed embryos which cannot emerge from the shell is a result of low relative humidity either during the holding period or in the incubators. The percentage of dead chicks at the seven-day test is related to variation in atmospheric temperature. The fluctuations in the percentage of mortality at 14 days corresponds with the variations in the relative humidity independent from temperature variations. The fluctuations in the percentage of mortality at 21 days corresponds with the variations in the atmospheric temperature independently from relative humidity variations.
SEASONAL VARIATION IN REPRODUCTION or FAYOMI
SUMMARY
3,947 eggs laid in 2 years by Fayomi hens were incubated throughout twelve months. The incubated eggs were examined at 7, 14 and 21 days of incubation to determine fertility, different stages of
mortality and different types of hatchability (pipped, partially emerged or hatched). 1(a) Minimum fertility percentage was reported in August with the maximum in April. (b) The average season fertility during spring, summer, autumn and winter was 87%, 72%, 80% and 9 1 % respectively. 2(a) The percentage of mortality at the 1st test reached a minimum during December and a maximum during August. (b) The percentage of embryos which died at the 2nd test or died in shell as well as percentage of total mortality was low during September and high during June. 3(a) The percentage of pipped, emerged or hatched chicks was low during June, while the highest was during March, April or September, respectively. (b) The percentage of hatchability was at its minimum during June and maximum during July and December. 4(a) The atmospheric temperature had more effect than relative humidity in respect to fertility. (b) Hatchability was affected by relative humidity independently of atmospheric temperature. 5(a) The practical application of this problem has been discussed. (b) A modified hatching season extending from August to December is recommended in relation to egg quality and male fertility in Egypt. REFERENCES Byerly, T. C , C. W. Knox and M. Jull, 1934. Some genetic aspects of hatchability. Poultry Sci. 13: 230-238. Cooney, W. T., 1943. Preincubation humidity varia-
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(1943) and Talmadge (1947). In the subtropics, it is suggested to modify the hatching season so as to coincide with the period extending from August to December. In this respect Hafez and Kamar (1955) have shown that Fayomi chickens hatched during these months show the best growth and egg production and attain sexual maturity very early at a relatively high body weight. It is the turn of poultry breeders to select new strains which would possess certain qualities of shell such as shell thickness and porosity, to facilitate emerging of chicks during hatching under subtropical conditions. Selecting cocks for high semen quality or for fertility during summer months is of no little importance. Examination of cocks used for breeding must be carried out periodically during the hatching season so as to eliminate cocks of temporary infertility. Further work is needed to find out the genetic, nutritional and pathological causes of this early embryonic mortality. Also the percentage of total mortality at the age of 21 days is considerably high during May and June. It is of no little importance to segregate the genetic and environmental factors concerned in this phenomenon. The study of the effects of increasing relative humidity in the storing rooms as well as incubators is of great interest in subtropical regions. These results are attributed to the environmental conditions of the hens rather than holding conditions for eggs. The latter factor could be made mechanically optimum whereas the former could not under practical conditions.
529
530
N. R. GYLES, G. E. DICKERSON, Q. B. KINDER AND H. L. KEMPSTER eggs as influenced by environment and heredity. Connecticut (Storrs) Agr. Exp. Sta. Bull. No. 262. North, M. O., 1941. High altitude incubation of eggs. U. S. Egg Poultry Mag. 47: 158-159, 184. Payne, L. F., and C. Ingram, 1927. The effects of freezing the combs of breeding males. Poultry Sci. 6: 99-107. Romanoff, A. L., and A. J. Romanoff, 1949. The Avian Egg. p. 27, Wiley, New York. Scott, H. M., 1933. The effect of age and holding temperatures on hatchability of turkey and chicken eggs. Poultry Sci. 12: 49-54. Talmadge, D. W., 1947. Effect of the storage temperatures on the hatchability of eggs. M.Sc. Thesis, Univ. of Massachusetts. Wilson, W. 0., and L. E. Johnson, 1946. The inheritance of egg production and hatchability in turkeys. Poultry Sci. 25: 278-284.
Initial and Actual Selection in Poultry 1 N. R. GYLES, 2 G. E. DICKERSON, 3 Q. B. KINDER AND H. L. KEMPSTER Departments of Animal and Poultry Husbandry, University of Missouri, Columbia (Received for publication August 17, 1953)
T
HE general improvement in various aspects of animal performance, over a number of years and in several countries, has been outlined by Lush (1951). Although the portion of such improvement which may be attributed to the selection of superior breeding stock cannot be determined precisely, there is little doubt that much of it is genetic. This interpretation is strengthened by the demonstrated power of selection to develop divergence in the performance of strains derived from the same original stock in rats (Morris et al., 1933), in chickens (Lamoreux et al.,
1 This paper includes results presented by the senior author as a doctoral dissertation. Published with the approval of the Director, Missouri Agricultural Experiment Station. 2 Now Poultry Geneticist, University of Arkansas, Fayetteville, Arkansas. 3 Now Geneticist, Kimber Farms, Inc., Niles, California.
1943), in swine (Krider et al., 1946; and Dickerson and Grimes, 1947), in mice (MacArthur, 1949), and in corn (Woodworth et al., 1952). Some poultry breeders have reported that continued improvement is discouragingly slow in egg production flocks which have achieved a high level of performance as the result of consistent selection over a long period of years. These flocks are reputed to be well managed and to base their selection of breeding stock on performance of individuals, sibs and progeny. A plateau in performance seems to have been reached, although the degree of determination by heredity remains relatively high for most individual traits. Information concerning the possible reasons for such "diminishing returns" from selection may suggest methods for making further progress.
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tions effects on chicken egg hatchability. Oregon Agr. Exp. Sta. Tech. Bull. No. 2. Funk, E. M., 1934. Factors influencing hatchability in the domestic fowl. Missouri Agr. Exp. Sta. Bull. No. 341. Hafez, E. S. E., 1954. Organ development in relation to egg laying capacity in the fowl. J. Agr. Sci. 45:148-155. Hafez, E. S. E., and G. A. R. Kamar, 1955. Sexual maturity and related phenomenon. J. Agr. Sci. 45: (In the Press). Hays, F. A., 1951. Fertility and hatchability in Rhode Island Reds. Poultry Sci. 30: 153. Heywang, B. W., 1944. Fertility and hatchability when the environmental temperature of chickens is high. Poultry Sci. 23: 334-339. Kamar, G. A. R., 1954. Developmental and physiological aspects in the reproduction of domestic fowl. M.Sc. Thesis, Cairo Univ., Egypt. Landauer, W., 1948. The hatchability of chicken