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The Influence of Pea Comb and Naked Neck on Apteria Width in Domestic Fowl
The Influence of Pea Comb and Naked Neck on Apteria Width in Domestic Fowl HENRY L. CLASSEN1 and J. ROBERT SMYTH, JR. Department of Veterinary and Animal Sciences, University of Massachusetts, Amherst, Massachusetts 01003 (Received for publication March 30, 1977)
Naked neck and pea comb are morphological traits caused by the incompletely dominant genes Na and P, respectively. The naked neck mutation results in a reduction in the pterylae or feather tracts, particularly the head tract, as well as the elimination of down and semiplumes from the apteria (Hutt, 1949). The P gene causes the characteristic pea comb and is associated with breast ridge, a slight ridge of thickened skin running lengthwise along the keel bone (Munro and Kosin, 1940; Crawford, 1961). This study was designed to study the effects of the P and Na genes on certain feather tracts. MATERIALS AND METHODS The population used in this study was segregating for the P and Na genes and had been maintained as a closed population for approximately 10 years. Within line matings were conducted in order to compare all combinations of pea comb and naked neck genotypes. Heterozygous Plp+ males were also mated to unrelated Brown Leghorn females. Determination of comb and breast ridge phenotype, sex and appropriate apteria widths were made at day of age. The sternal apterium (SA) was measured on na+/na+ and Na/na+ chicks, while the lateral pelvic apterium (LPA) was measured on Na/na+ and Na/Na birds. The SA and LPA measurements were made at approximately mid-breast and above the hip joint, respectively. A total of 1020 birds were
1
Present address: Poultry Science Department, Pennsylvania State University, University Park, Pennsylvania 16802.
examined in this study. Harvey's least-squares analysis of variance for unequal sublcass numbers was used to determine the significance of pea comb and naked neck effects. RESULTS AND DISCUSSION The effects of comb and naked neck genotype on apteria width are summarized in Table 1. The results of the analysis of variance indicated that the pea comb effect on both the SA and LPA width was statistically significant (P<0.001). Similarly, the naked neck gene was found to reduce apteria width significantly (P<0.001). Other main effects in this analysis included sire family and sex of chicks. Sire family effects were found to be statistically significant (P<0.001) for all apteria measurements except the SA measurement on na+/na+ chicks. The effect of sex was significant only in the case of the SA measurements of Na/na+ birds. A significant sire family X comb genotype interaction (P<0.05) on the apteria width of Na/na+ chicks was also observed. This is probably due to the effects of residual genotype differences among sires. An analysis of variance of data from matings where only four genotypes (P/p+ Na/na+;P/p + na+/na+; p+/p+ Na/na+; and p+lp+ na+lna+) were segregating confirmed the effects of P and Na on apteria width. When P and Na were present in the same genotype, a significant interaction effect resulted (P<0.05) suggesting that their combined effect on apteria width exceeds the sum of their individual effects. To determine if there is a dosage effect of the P allele on apteria width, PIP males were mated to both P/p+ a n d p + / p + (single combed)
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Downloaded from http://ps.oxfordjournals.org/ at Northern Arizona University on May 25, 2015
ABSTRACT The effects of pea comb (P) and naked neck (Na) genes on apteria width were examined on 1020 chicks. Either Na or P resulted in significantly (P<0.001) increased sternal and lateral pelvic apteria width. When present together these mutations interacted resulting in a further increase in apteria width (P<0.05). Both P and Na mutations showed a dosage effect on feather tract width. Poultry Science 56:1683-1685, 1977
H. L. CLASSEN AND R. SMYTH, JR.
1684
TABLE 1.—The effect of comb genotype on sternal (SA) and lateral pelvic (LPA) apteria width of day old chicks Naked neck genotype na + /na +
Na/na +
Na/Na
Comb genotype
No. of chicks
SA
No. of chicks
SA
LPA
No. of chicks
LPA
P/p+ p+/p+
60 57
6.8 1 5.7
295 307
10.5 7.8
13.4 9.5
38 49
16.7 12.4
1
Mean apteria width in millimeters.
Naked neck genotypes na + /na +
Na/na +
Comb genotype
No. of chicks
SA
No. of chicks
SA
LPA
P/P + P/p+ P/p +
57 32
7.3 1 6.2
81 44
11.0 10.2
13.4 12.9
1
Mean apteria width in millimeters.
females. Offspring from t h e Plp + females would be present in an expected ratio of 1 PIP: 1 P/p+, while t h o s e from t h e p+lp+ birds would all be P/p+. T h e results of these matings are shown in Table 2. T h e presence of PIP offspring significantly increased apteria width for na+l na+ ( P < 0 . 0 0 1 ) and Nalna+ ( P < 0 . 0 1 ) chicks, while t h e increase n o t e d for t h e LPA for Nalna+ closely a p p r o a c h e d significance at t h e 5% level. As suggested b y Crawford ( 1 9 7 6 ) , t h e r e is a dosage effect on apteria w i d t h s associated with t h e Na allele (Table 1). T h e effect of t h e pea c o m b gene on p t e r y l a e w i d t h , a n d therefore feather coverage, m a y be related t o t h e incidence of breast blisters. It has been established previously t h a t t h e incidence of breast blisters is related t o breast feathering ( F u n k and Savage, 1 9 5 6 ; Kondra and Cavers, 1 9 4 7 ; a n d Gyles et al, 1 9 6 2 ) . These data suggest t h a t pea c o m b e d birds might be expected t o have a higher incidence of breast blisters. Such a relationship was r e p o r t e d b y H a r t m a n n ( 1 9 7 2 ) w h o f o u n d t h a t pea c o m b e d broilers had significantly m o r e breast blisters t h a n did their single c o m b sibs. More recently, Wesley and Weaver ( 1 9 7 4 ) failed t o confirm this r e l a t i o n s h i p ; however, t h e y did n o t m a k e
sib comparisons. Observations o n t h e incidence of t h e breast ridge p h e n o t y p e s u p p o r t e d t h e hypothesis suggested by M u n r o and Kosin ( 1 9 4 0 ) and Crawford ( 1 9 6 1 ) t h a t it is a pleiotropic effect of t h e pea c o m b gene. T h e rare cases where pea c o m b chicks showed n o breast ridge at day of age either showed t h e trait at 8 weeks of age or p r o d u c e d it in offspring f r o m a p p r o p r i a t e test matings. Therefore, these few exceptions were n o t t h e result of a crossover involving t w o closely linked genes, b u t p r o b a b l y d u e t o t h e modifying effects of t h e residual g e n o t y p e .
REFERENCES Crawford, R. D., 1961. Breast ridge, associated with pea and walnut comb, as an aid in identifying comb type. Poultry Sci. 4 0 : 2 6 2 - 2 6 3 . Crawford, R. D., 1976. Incomplete dominance of the gene for naked neck in domestic fowl. Poultry Sci. 55:820-822. Funk, E. M., and J. E. Savage, 1956. The incidence of breast blisters as related to the amount of breast feathering. Poultry Sci. 35:1399-1400. Gyles, N. R., J. Kan and R. M. Smith, 1962. The heritability of breast blister condition and breast feather coverage in a White Rock broiler strain. Poultry Sci. 4 1 : 1 3 - 1 7 . Hartmann, W., 1972. Relationship between genes at
Downloaded from http://ps.oxfordjournals.org/ at Northern Arizona University on May 25, 2015
TABLE 2.—The effect ofP allele dosage on sternal (SA) and lateral pelvic (LPA) apteria width
RESEARCH NOTE the pea and single comb locus and economic traits in broiler chicken. Br. Poultry Sci. 13:305-309. Hutt, F. B., 1949. Genetics of the Fowl. McGraw-Hill Book Co., Inc., New York. Kondra, P. A., and J. R. Cavers, 1947. Relation of the rate of feathering to the development of keel bursae. Poultry Sci. 2 6 : 8 3 - 8 5 .
1685
Munro, S. S., and I. L. Kosin, 1940. Breast ridge in domestic fowl, a new dominant character linked with pea comb or another expression of the pea comb gene? Am. Nat. 74:383-384. Wesley, R. L., and W. D. Weaver, Jr., 1974. Some factors affecting the incidence of breast blisters in commercial broilers. Poultry Sci. 53:1991.
Downloaded from http://ps.oxfordjournals.org/ at Northern Arizona University on May 25, 2015
Naked neck and pea comb are morphological traits caused by the incompletely dominant genes Na and P, respectively. The naked neck mutation results in a reduction in the pterylae or feather tracts, particularly the head tract, as well as the elimination of down and semiplumes from the apteria (Hutt, 1949). The P gene causes the characteristic pea comb and is associated with breast ridge, a slight ridge of thickened skin running lengthwise along the keel bone (Munro and Kosin, 1940; Crawford, 1961). This study was designed to study the effects of the P and Na genes on certain feather tracts. MATERIALS AND METHODS The population used in this study was segregating for the P and Na genes and had been maintained as a closed population for approximately 10 years. Within line matings were conducted in order to compare all combinations of pea comb and naked neck genotypes. Heterozygous Plp+ males were also mated to unrelated Brown Leghorn females. Determination of comb and breast ridge phenotype, sex and appropriate apteria widths were made at day of age. The sternal apterium (SA) was measured on na+/na+ and Na/na+ chicks, while the lateral pelvic apterium (LPA) was measured on Na/na+ and Na/Na birds. The SA and LPA measurements were made at approximately mid-breast and above the hip joint, respectively. A total of 1020 birds were
1
Present address: Poultry Science Department, Pennsylvania State University, University Park, Pennsylvania 16802.
examined in this study. Harvey's least-squares analysis of variance for unequal sublcass numbers was used to determine the significance of pea comb and naked neck effects. RESULTS AND DISCUSSION The effects of comb and naked neck genotype on apteria width are summarized in Table 1. The results of the analysis of variance indicated that the pea comb effect on both the SA and LPA width was statistically significant (P<0.001). Similarly, the naked neck gene was found to reduce apteria width significantly (P<0.001). Other main effects in this analysis included sire family and sex of chicks. Sire family effects were found to be statistically significant (P<0.001) for all apteria measurements except the SA measurement on na+/na+ chicks. The effect of sex was significant only in the case of the SA measurements of Na/na+ birds. A significant sire family X comb genotype interaction (P<0.05) on the apteria width of Na/na+ chicks was also observed. This is probably due to the effects of residual genotype differences among sires. An analysis of variance of data from matings where only four genotypes (P/p+ Na/na+;P/p + na+/na+; p+/p+ Na/na+; and p+lp+ na+lna+) were segregating confirmed the effects of P and Na on apteria width. When P and Na were present in the same genotype, a significant interaction effect resulted (P<0.05) suggesting that their combined effect on apteria width exceeds the sum of their individual effects. To determine if there is a dosage effect of the P allele on apteria width, PIP males were mated to both P/p+ a n d p + / p + (single combed)
1683
Downloaded from http://ps.oxfordjournals.org/ at Northern Arizona University on May 25, 2015
ABSTRACT The effects of pea comb (P) and naked neck (Na) genes on apteria width were examined on 1020 chicks. Either Na or P resulted in significantly (P<0.001) increased sternal and lateral pelvic apteria width. When present together these mutations interacted resulting in a further increase in apteria width (P<0.05). Both P and Na mutations showed a dosage effect on feather tract width. Poultry Science 56:1683-1685, 1977
H. L. CLASSEN AND R. SMYTH, JR.
1684
TABLE 1.—The effect of comb genotype on sternal (SA) and lateral pelvic (LPA) apteria width of day old chicks Naked neck genotype na + /na +
Na/na +
Na/Na
Comb genotype
No. of chicks
SA
No. of chicks
SA
LPA
No. of chicks
LPA
P/p+ p+/p+
60 57
6.8 1 5.7
295 307
10.5 7.8
13.4 9.5
38 49
16.7 12.4
1
Mean apteria width in millimeters.
Naked neck genotypes na + /na +
Na/na +
Comb genotype
No. of chicks
SA
No. of chicks
SA
LPA
P/P + P/p+ P/p +
57 32
7.3 1 6.2
81 44
11.0 10.2
13.4 12.9
1
Mean apteria width in millimeters.
females. Offspring from t h e Plp + females would be present in an expected ratio of 1 PIP: 1 P/p+, while t h o s e from t h e p+lp+ birds would all be P/p+. T h e results of these matings are shown in Table 2. T h e presence of PIP offspring significantly increased apteria width for na+l na+ ( P < 0 . 0 0 1 ) and Nalna+ ( P < 0 . 0 1 ) chicks, while t h e increase n o t e d for t h e LPA for Nalna+ closely a p p r o a c h e d significance at t h e 5% level. As suggested b y Crawford ( 1 9 7 6 ) , t h e r e is a dosage effect on apteria w i d t h s associated with t h e Na allele (Table 1). T h e effect of t h e pea c o m b gene on p t e r y l a e w i d t h , a n d therefore feather coverage, m a y be related t o t h e incidence of breast blisters. It has been established previously t h a t t h e incidence of breast blisters is related t o breast feathering ( F u n k and Savage, 1 9 5 6 ; Kondra and Cavers, 1 9 4 7 ; a n d Gyles et al, 1 9 6 2 ) . These data suggest t h a t pea c o m b e d birds might be expected t o have a higher incidence of breast blisters. Such a relationship was r e p o r t e d b y H a r t m a n n ( 1 9 7 2 ) w h o f o u n d t h a t pea c o m b e d broilers had significantly m o r e breast blisters t h a n did their single c o m b sibs. More recently, Wesley and Weaver ( 1 9 7 4 ) failed t o confirm this r e l a t i o n s h i p ; however, t h e y did n o t m a k e
sib comparisons. Observations o n t h e incidence of t h e breast ridge p h e n o t y p e s u p p o r t e d t h e hypothesis suggested by M u n r o and Kosin ( 1 9 4 0 ) and Crawford ( 1 9 6 1 ) t h a t it is a pleiotropic effect of t h e pea c o m b gene. T h e rare cases where pea c o m b chicks showed n o breast ridge at day of age either showed t h e trait at 8 weeks of age or p r o d u c e d it in offspring f r o m a p p r o p r i a t e test matings. Therefore, these few exceptions were n o t t h e result of a crossover involving t w o closely linked genes, b u t p r o b a b l y d u e t o t h e modifying effects of t h e residual g e n o t y p e .
REFERENCES Crawford, R. D., 1961. Breast ridge, associated with pea and walnut comb, as an aid in identifying comb type. Poultry Sci. 4 0 : 2 6 2 - 2 6 3 . Crawford, R. D., 1976. Incomplete dominance of the gene for naked neck in domestic fowl. Poultry Sci. 55:820-822. Funk, E. M., and J. E. Savage, 1956. The incidence of breast blisters as related to the amount of breast feathering. Poultry Sci. 35:1399-1400. Gyles, N. R., J. Kan and R. M. Smith, 1962. The heritability of breast blister condition and breast feather coverage in a White Rock broiler strain. Poultry Sci. 4 1 : 1 3 - 1 7 . Hartmann, W., 1972. Relationship between genes at
Downloaded from http://ps.oxfordjournals.org/ at Northern Arizona University on May 25, 2015
TABLE 2.—The effect ofP allele dosage on sternal (SA) and lateral pelvic (LPA) apteria width
RESEARCH NOTE the pea and single comb locus and economic traits in broiler chicken. Br. Poultry Sci. 13:305-309. Hutt, F. B., 1949. Genetics of the Fowl. McGraw-Hill Book Co., Inc., New York. Kondra, P. A., and J. R. Cavers, 1947. Relation of the rate of feathering to the development of keel bursae. Poultry Sci. 2 6 : 8 3 - 8 5 .
1685
Munro, S. S., and I. L. Kosin, 1940. Breast ridge in domestic fowl, a new dominant character linked with pea comb or another expression of the pea comb gene? Am. Nat. 74:383-384. Wesley, R. L., and W. D. Weaver, Jr., 1974. Some factors affecting the incidence of breast blisters in commercial broilers. Poultry Sci. 53:1991.
Downloaded from http://ps.oxfordjournals.org/ at Northern Arizona University on May 25, 2015