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Hereditary Chondrodystrophy in the Turkey1
BREEDING AND GENETICS Hereditary Chondrodystrophy in the Turkey1 KARL E. NESTOR Department of Poultry Science, Ohio Agricultural Research and Development Wooster, Ohio 44691
Center,
(Received for publication April 25, 1977)
INTRODUCTION Hereditary c h o n d r o d y s t r o p h y has been rep o r t e d in t h e chicken ( A s m u n d s o n , 1 9 4 2 ; L a m o r e u x , 1 9 4 2 ; Hays, 1 9 4 4 ) . All t y p e s involved shortening of t h e long b o n e s of t h e legs and wings. In t h e t y p e r e p o r t e d b y Hays ( 1 9 4 4 ) , t h e tibiae were always straight whereas t h e tibiae s o m e t i m e s were e x t r e m e l y b e n t in the type reported by Lamoreux (1942). Lamoreux as well as A s m u n d s o n ( 1 9 4 2 ) also observed an e x t r e m e shortening of t h e lower beak with corresponding overgrowth of t h e upper beak t o give a " p a r r o t - b e a k " a p p e a r a n c e . Both t h e u p p e r and lower beaks were p r o p o r t i o n a l l y shortened in the form studied by Hays ( 1 9 4 4 ) . T h e m u t a t i o n s in all cases were semi-lethal or lethal and were caused by a u t o s o m a l recessive genes.
MATERIALS AND METHODS
A s m u n d s o n ( 1 9 4 4 ) found a semi-lethal a u t o somal genes, given t h e s y m b o l s, in t u r k e y s which involved shortening and thickening of t h e long bones of t h e legs and wings. Only a b o u t 19% of t h e h o m o z y g o u s individuals (s s) h a t c h e d . T h e h e t e r o z y g o t e (S s) had shorter shanks t h a n t h e h o m o z y g o u s n o r m a l (S S) so t h e S gene was incompletely d o m i n a n t . T h e length of t h e beak apparently was n o t affected. Gaffney ( 1 9 7 5 ) r e p o r t e d a c o m p l e t e l y lethal
1 Approved for publication as Journal Article No. 57-77 of the Ohio Agricultural Research and Development Center, Wooster, Ohio 44691.
1978 Poultry Sci 57:577-580
c h o n d r o d y s t r o p h i c condition which was inherited by an a u t o s o m a l recessive gene designated ch. H o m o z y g o u s individuals {ch ch) h a d shortened and t h i c k e n e d femur, tibia, and metatarsal bones. T h e lower mandible was s h o r t e n e d resulting in t h e " p a r r o t - b e a k " a p p e a r a n c e in s o m e individuals. A f o r m of c h o n d r o d y s t r o p h y similar t o , b u t n o t identical with, those observed b y Hays ( 1 9 4 4 ) , A s m u n d s o n ( 1 9 4 4 ) , and Gaffney ( 1 9 7 5 ) was observed a m o n g t h e offspring of one hen from an inbred line of t u r k e y s maintained b y parent-offspring or brother-sister matings. T h e p u r p o s e of this e x p e r i m e n t was t o study t h e inheritance of this n e w form of c h o n d r o d y s t r o p h y and to estimate t h e frequency of o c c u r r e n c e in various genetic stocks.
T h e t w o original c h o n d r o d y s t r o p h i c p o u l t s were observed in t h e offspring of o n e hen from an inbred line of large white t u r k e y s . Both poults were characterized b y s h o r t e n e d and thickened long b o n e s of t h e legs and wings, p r o p o r t i o n a l l y s h o r t e n e d beaks, and missing phalanges o n t h e feet. Only one of t h e t w o survived t o m a t u r i t y . This a p p a r e n t female was stimulated b y artificial light b u t failed t o lay any eggs. T h e shortening and thickening of t h e long b o n e s of t h e shank is s h o w n in Figure 1. N o t e t h e missing terminal phalanges on s o m e of t h e digits. A l t h o u g h this bird had s o m e difficulty walking, it could move a r o u n d t h e pen
577
Downloaded from http://ps.oxfordjournals.org/ at Purdue University Libraries ADMN on June 19, 2015
ABSTRACT A new form of chondrodystrophy was observed in an inbred line of large weight white turkeys. It is characterized by shortened and thickened long bones of the legs and wings and proportionally shortened beaks. The absence of some terminal phalanges was noted in about half of the mutants. A hydrocephalous condition was observed in a few mutants but was not found in normal embryos. The chondrodystrophy is caused by an autosomal recessive semi-lethal gene designated chm. Only three chm chm individuals have hatched normally but others have been assisted out of the shell and have survived for varying periods of time. Of six that survived to mature age, all were sterile. A slightly different form of chondrodystrophy was observed in medium-weight turkeys from three sources. This type, which did not have the missing phalanges or hydrocephalic expression, was also caused by a recessive gene which was different from chm. Phenotypically, they differed from s s embryos (Asmundson, 1944) by shortening of the beak and failure to hatch.
578
NESTOR
FIG. 1. The shanks of the original chondrodystrophic turkey exhibiting missing phalanges.
well enough to obtain feed and water. Body weight was greatly reduced. Figure 2 shows the comparable sizes of the chondrodystrophic turkey on the right with its normal sister on the left. This chondrodystrophic bird survived for two years. Brothers and sisters of the original chondrodystrophic poults were mated inter se in the first generation. In subsequent generations offspring from known carriers were mated together to study the inheritance of the abnormality. All unhatched fertile eggs were broken after 28 days of incubation. Any live chondrodystrophic poults were assisted out of the shell and an attempt was made to rear these poults. They were reared in small groups of three or less in separate facilities from their normal counterparts. The toes of each chondrodystrophic poults were checked for the absence of phalanges. The sex of most of the unhatched, dead embryos was obtained by autopsy. Samples of nonpedigreed eggs were obtained
f
FIG. 2. A comparison of the original chondrodystrophic turkey with its normal sister at maturity.
RESULTS AND DISCUSSION
The ratio of normal to chondrodystrophic individuals among embryos and hatched poults in the matings which produced affected embryos was 107:24 which does not differ significantly (chi-square = 3.0) from the expected ratio (3:1) based on the assumption that chondrodystrophy was caused by a recessive gene. Of 16 unhatched chondrodystrophic embryos or poults which were helped out of the shell and died soon after placing on food and water, 9 were males and 7 were females, suggesting that the gene was autosomal. It is proposed to designate the gene with the symbol chm which would distinguish it from the ch and x symbol given to a different chondrodystrophic conditions by Gaffney (1975) and Asmundson (1944), respectively. Of 14 poults which either hatched naturally (3) or were assisted from the shell (11), only six survived to maturity, but all did not develop sexually when stimulated by artificial light. The chromosomal karyotypes of four individuals were obtained by Fechheimer (1977, unpublished data). Based on outward appearance, three of these were females and one was a male. However, the karotypes revealed that they were all genetic females bearing the ZW sex chromosome complements. All of the mutant embryos and poults had noticeably thickened and shortened long bones in the legs and wings and proportionally shortened upper and lower beaks. Twelve of the 26 chondrodystrophic individuals had missing phalanges on one or more digits. There was no consistent pattern between individuals for the absence of phalanges. Variation also existed between the left and right feet of the same individuals. A hydrocephalic condition was noted in a few chondrodystrophic embryos which had died previous to observation but not
Downloaded from http://ps.oxfordjournals.org/ at Purdue University Libraries ADMN on June 19, 2015
from three commercial strains of medium weight turkeys in order to determine whether chondrodystrophy occurred in these strains. Two of the strains, a white and a bronze, were from the same breeder and it was not known if the two strains were related. All unhatched fertile eggs were broken and examined macroscopically for chondrodystrophic embryos. Random samples of the normal turkeys were mated reciprocally Inter se and one strain was mated reciprocally with known heterozygotes from the original chondrodystrophic stock.
HEREDITARY CHONDRODYSTROPHY IN TURKEYS
The eggs containing unhatched embryos from the two strains of medium-weight turkeys from the second commercial breeder were broken and examined for the presence of chondrodystrophic embryos after 28 days of incubation. Twenty-five out of a total of 53 embryos in the white strain and 14 of a total of 99 embryos of the bronze strain were classified as chondrodystrophic. Many of these embryos were alive but none pipped the shell. All exhibited shortened and thickened long bones of legs and wings, proportionally shortened
beak, and the normal number of phalanges on the digits. Offspring from the white strain were used for test mating with known Chm chm individuals from the original stock. Two males of the commercial strain were artificially mated to two females of the commercial strain and two Cbm cbm females of the original stock. In addition, two Chm chm males were artificially mated to two females of the commercial strain. When males and females of the commercial strain were mated inter se, 28 normal and 7 chondrodystrophic individuals were produced. This did not differ significantly from a 3:1 ratio, suggesting that this chondrodystrophy was produced by a single recessive gene. When the same males were mated to Chm cbm females, a total of 20 normal embryos and poults were produced indicating that the two types of chondrodystrophy were caused by different genes. In addition, where two Chm chm males were artificially mated to two females of the commercial strain, all normal embryos and poults (22 total) were produced. This further suggests that two different genes were present in the two stocks. Since chondrodystrophy was observed in three commercial medium-weight strains, and this form of chondrodystrophy was different from that originally found in the large-bodied inbred line, the medium-weight strains maintained in genetic studies were surveyed for individuals with shanks extremely short for their body weight. These lines originated from a randombred control (McCartney, 1964) established in 1957. A total of 6 such females were mated to unrelated males. All offspring were normal. The ¥± individuals were mated inter se within hens. Chondrodystrophy of the type found in the commercial strains was observed in two of the six groups. The chondrodystrophy observed in the commercial strains appears to be similar to the short turkeys described by Asmundson (1944). However, many of his embryos hatched whereas no chondrodystrophic poults were observed among those that hatched from the three commercial strains. Also, Asmundson (1944) did not report any shortening of the beak whereas all chondrodystrophic embryos from the commercial strains had shortened beaks. Nevertheless, no symbol will be given to this form of chondrodystrophy since it may represent a slightly different expression of the s gene of Asmundson (1944).
Downloaded from http://ps.oxfordjournals.org/ at Purdue University Libraries ADMN on June 19, 2015
in their normal counterparts. Most of the mutant embryos survived to 28 days of incubation. Only two embryos died at an earlier age. Egg production and fertility of the Cbm chm and &}"> Chm females were similar. Hatchability of fertile eggs was also similar if the chm chm embryos were omitted from the total eggs set. Thus it appears that the chm gene does not have a detrimental effect on reproduction in Chm cbm heterozygoes if the homozygous offspring were omitted from the analysis. However, hatchability of fertile eggs was significantly reduced in Chm chm hens if chm chm offspring were included. The shank length of Chm Chm and Chmchm hens was not noticeably different. Actual measurements made on a few individuals in the last generation were similar for the two types of females. A sample of one commercial medium weight strain was grown until 24 weeks of age. At this time shank length was measured and the 4 males and 4 females with the shortest shanks out of a total of approximately 75 individuals for each sex were selected and mated together in pairs. This selection was not done to isolate individuals carrying chm but rather to isolate other types of chondrodystrophy resulting in shortened shanks. Egg production was low for all 4 females. Two females produced only normal embryos and poults (total of 12). One • of the other females had 5 normal poults and embryos and 1 chondrodystrophic embryo. The remaining female produced 7 normal and 2 chondrodystrophic individuals. The chondrodystrophic embryos were similar to those described previously except all had the normal number of phalanges. None of the chondrodystrophic embryos were alive at observation. In the offspring of the 2 females which produced the chondrodystrophic embryos, the ratio was 13 normal to 3 chondrodystrophic suggesting a recessive gene.
579
580
NESTOR REFERENCES
Asmundson, V. S., 1942. An inherited micromelia in the domestic fowl. J. Heredity 33:328-330. Asmundson, V. S., 1944. Inherited shortening of the long bones in the turkey. J. Heredity 35:295—299. Gaffney, L. J., 1975. Chondrodystrophy: An inherited lethal condition in turkey embryos. J. Heredity
66:339-343. Hays, F. A., 1944. Chondrodystrophy in Rhode Island Reds. Amer. Nat. 7 8 : 5 4 - 5 8 . Lamoreux, W. F., 1942. Hereditary chondrodystrophy in the fowl. J. Heredity 33:275-283. McCartney, M. G., 1964. A randombred control population of turkeys. Poultry Sci. 43:739—749.
Downloaded from http://ps.oxfordjournals.org/ at Purdue University Libraries ADMN on June 19, 2015
Center,
(Received for publication April 25, 1977)
INTRODUCTION Hereditary c h o n d r o d y s t r o p h y has been rep o r t e d in t h e chicken ( A s m u n d s o n , 1 9 4 2 ; L a m o r e u x , 1 9 4 2 ; Hays, 1 9 4 4 ) . All t y p e s involved shortening of t h e long b o n e s of t h e legs and wings. In t h e t y p e r e p o r t e d b y Hays ( 1 9 4 4 ) , t h e tibiae were always straight whereas t h e tibiae s o m e t i m e s were e x t r e m e l y b e n t in the type reported by Lamoreux (1942). Lamoreux as well as A s m u n d s o n ( 1 9 4 2 ) also observed an e x t r e m e shortening of t h e lower beak with corresponding overgrowth of t h e upper beak t o give a " p a r r o t - b e a k " a p p e a r a n c e . Both t h e u p p e r and lower beaks were p r o p o r t i o n a l l y shortened in the form studied by Hays ( 1 9 4 4 ) . T h e m u t a t i o n s in all cases were semi-lethal or lethal and were caused by a u t o s o m a l recessive genes.
MATERIALS AND METHODS
A s m u n d s o n ( 1 9 4 4 ) found a semi-lethal a u t o somal genes, given t h e s y m b o l s, in t u r k e y s which involved shortening and thickening of t h e long bones of t h e legs and wings. Only a b o u t 19% of t h e h o m o z y g o u s individuals (s s) h a t c h e d . T h e h e t e r o z y g o t e (S s) had shorter shanks t h a n t h e h o m o z y g o u s n o r m a l (S S) so t h e S gene was incompletely d o m i n a n t . T h e length of t h e beak apparently was n o t affected. Gaffney ( 1 9 7 5 ) r e p o r t e d a c o m p l e t e l y lethal
1 Approved for publication as Journal Article No. 57-77 of the Ohio Agricultural Research and Development Center, Wooster, Ohio 44691.
1978 Poultry Sci 57:577-580
c h o n d r o d y s t r o p h i c condition which was inherited by an a u t o s o m a l recessive gene designated ch. H o m o z y g o u s individuals {ch ch) h a d shortened and t h i c k e n e d femur, tibia, and metatarsal bones. T h e lower mandible was s h o r t e n e d resulting in t h e " p a r r o t - b e a k " a p p e a r a n c e in s o m e individuals. A f o r m of c h o n d r o d y s t r o p h y similar t o , b u t n o t identical with, those observed b y Hays ( 1 9 4 4 ) , A s m u n d s o n ( 1 9 4 4 ) , and Gaffney ( 1 9 7 5 ) was observed a m o n g t h e offspring of one hen from an inbred line of t u r k e y s maintained b y parent-offspring or brother-sister matings. T h e p u r p o s e of this e x p e r i m e n t was t o study t h e inheritance of this n e w form of c h o n d r o d y s t r o p h y and to estimate t h e frequency of o c c u r r e n c e in various genetic stocks.
T h e t w o original c h o n d r o d y s t r o p h i c p o u l t s were observed in t h e offspring of o n e hen from an inbred line of large white t u r k e y s . Both poults were characterized b y s h o r t e n e d and thickened long b o n e s of t h e legs and wings, p r o p o r t i o n a l l y s h o r t e n e d beaks, and missing phalanges o n t h e feet. Only one of t h e t w o survived t o m a t u r i t y . This a p p a r e n t female was stimulated b y artificial light b u t failed t o lay any eggs. T h e shortening and thickening of t h e long b o n e s of t h e shank is s h o w n in Figure 1. N o t e t h e missing terminal phalanges on s o m e of t h e digits. A l t h o u g h this bird had s o m e difficulty walking, it could move a r o u n d t h e pen
577
Downloaded from http://ps.oxfordjournals.org/ at Purdue University Libraries ADMN on June 19, 2015
ABSTRACT A new form of chondrodystrophy was observed in an inbred line of large weight white turkeys. It is characterized by shortened and thickened long bones of the legs and wings and proportionally shortened beaks. The absence of some terminal phalanges was noted in about half of the mutants. A hydrocephalous condition was observed in a few mutants but was not found in normal embryos. The chondrodystrophy is caused by an autosomal recessive semi-lethal gene designated chm. Only three chm chm individuals have hatched normally but others have been assisted out of the shell and have survived for varying periods of time. Of six that survived to mature age, all were sterile. A slightly different form of chondrodystrophy was observed in medium-weight turkeys from three sources. This type, which did not have the missing phalanges or hydrocephalic expression, was also caused by a recessive gene which was different from chm. Phenotypically, they differed from s s embryos (Asmundson, 1944) by shortening of the beak and failure to hatch.
578
NESTOR
FIG. 1. The shanks of the original chondrodystrophic turkey exhibiting missing phalanges.
well enough to obtain feed and water. Body weight was greatly reduced. Figure 2 shows the comparable sizes of the chondrodystrophic turkey on the right with its normal sister on the left. This chondrodystrophic bird survived for two years. Brothers and sisters of the original chondrodystrophic poults were mated inter se in the first generation. In subsequent generations offspring from known carriers were mated together to study the inheritance of the abnormality. All unhatched fertile eggs were broken after 28 days of incubation. Any live chondrodystrophic poults were assisted out of the shell and an attempt was made to rear these poults. They were reared in small groups of three or less in separate facilities from their normal counterparts. The toes of each chondrodystrophic poults were checked for the absence of phalanges. The sex of most of the unhatched, dead embryos was obtained by autopsy. Samples of nonpedigreed eggs were obtained
f
FIG. 2. A comparison of the original chondrodystrophic turkey with its normal sister at maturity.
RESULTS AND DISCUSSION
The ratio of normal to chondrodystrophic individuals among embryos and hatched poults in the matings which produced affected embryos was 107:24 which does not differ significantly (chi-square = 3.0) from the expected ratio (3:1) based on the assumption that chondrodystrophy was caused by a recessive gene. Of 16 unhatched chondrodystrophic embryos or poults which were helped out of the shell and died soon after placing on food and water, 9 were males and 7 were females, suggesting that the gene was autosomal. It is proposed to designate the gene with the symbol chm which would distinguish it from the ch and x symbol given to a different chondrodystrophic conditions by Gaffney (1975) and Asmundson (1944), respectively. Of 14 poults which either hatched naturally (3) or were assisted from the shell (11), only six survived to maturity, but all did not develop sexually when stimulated by artificial light. The chromosomal karyotypes of four individuals were obtained by Fechheimer (1977, unpublished data). Based on outward appearance, three of these were females and one was a male. However, the karotypes revealed that they were all genetic females bearing the ZW sex chromosome complements. All of the mutant embryos and poults had noticeably thickened and shortened long bones in the legs and wings and proportionally shortened upper and lower beaks. Twelve of the 26 chondrodystrophic individuals had missing phalanges on one or more digits. There was no consistent pattern between individuals for the absence of phalanges. Variation also existed between the left and right feet of the same individuals. A hydrocephalic condition was noted in a few chondrodystrophic embryos which had died previous to observation but not
Downloaded from http://ps.oxfordjournals.org/ at Purdue University Libraries ADMN on June 19, 2015
from three commercial strains of medium weight turkeys in order to determine whether chondrodystrophy occurred in these strains. Two of the strains, a white and a bronze, were from the same breeder and it was not known if the two strains were related. All unhatched fertile eggs were broken and examined macroscopically for chondrodystrophic embryos. Random samples of the normal turkeys were mated reciprocally Inter se and one strain was mated reciprocally with known heterozygotes from the original chondrodystrophic stock.
HEREDITARY CHONDRODYSTROPHY IN TURKEYS
The eggs containing unhatched embryos from the two strains of medium-weight turkeys from the second commercial breeder were broken and examined for the presence of chondrodystrophic embryos after 28 days of incubation. Twenty-five out of a total of 53 embryos in the white strain and 14 of a total of 99 embryos of the bronze strain were classified as chondrodystrophic. Many of these embryos were alive but none pipped the shell. All exhibited shortened and thickened long bones of legs and wings, proportionally shortened
beak, and the normal number of phalanges on the digits. Offspring from the white strain were used for test mating with known Chm chm individuals from the original stock. Two males of the commercial strain were artificially mated to two females of the commercial strain and two Cbm cbm females of the original stock. In addition, two Chm chm males were artificially mated to two females of the commercial strain. When males and females of the commercial strain were mated inter se, 28 normal and 7 chondrodystrophic individuals were produced. This did not differ significantly from a 3:1 ratio, suggesting that this chondrodystrophy was produced by a single recessive gene. When the same males were mated to Chm cbm females, a total of 20 normal embryos and poults were produced indicating that the two types of chondrodystrophy were caused by different genes. In addition, where two Chm chm males were artificially mated to two females of the commercial strain, all normal embryos and poults (22 total) were produced. This further suggests that two different genes were present in the two stocks. Since chondrodystrophy was observed in three commercial medium-weight strains, and this form of chondrodystrophy was different from that originally found in the large-bodied inbred line, the medium-weight strains maintained in genetic studies were surveyed for individuals with shanks extremely short for their body weight. These lines originated from a randombred control (McCartney, 1964) established in 1957. A total of 6 such females were mated to unrelated males. All offspring were normal. The ¥± individuals were mated inter se within hens. Chondrodystrophy of the type found in the commercial strains was observed in two of the six groups. The chondrodystrophy observed in the commercial strains appears to be similar to the short turkeys described by Asmundson (1944). However, many of his embryos hatched whereas no chondrodystrophic poults were observed among those that hatched from the three commercial strains. Also, Asmundson (1944) did not report any shortening of the beak whereas all chondrodystrophic embryos from the commercial strains had shortened beaks. Nevertheless, no symbol will be given to this form of chondrodystrophy since it may represent a slightly different expression of the s gene of Asmundson (1944).
Downloaded from http://ps.oxfordjournals.org/ at Purdue University Libraries ADMN on June 19, 2015
in their normal counterparts. Most of the mutant embryos survived to 28 days of incubation. Only two embryos died at an earlier age. Egg production and fertility of the Cbm chm and &}"> Chm females were similar. Hatchability of fertile eggs was also similar if the chm chm embryos were omitted from the total eggs set. Thus it appears that the chm gene does not have a detrimental effect on reproduction in Chm cbm heterozygoes if the homozygous offspring were omitted from the analysis. However, hatchability of fertile eggs was significantly reduced in Chm chm hens if chm chm offspring were included. The shank length of Chm Chm and Chmchm hens was not noticeably different. Actual measurements made on a few individuals in the last generation were similar for the two types of females. A sample of one commercial medium weight strain was grown until 24 weeks of age. At this time shank length was measured and the 4 males and 4 females with the shortest shanks out of a total of approximately 75 individuals for each sex were selected and mated together in pairs. This selection was not done to isolate individuals carrying chm but rather to isolate other types of chondrodystrophy resulting in shortened shanks. Egg production was low for all 4 females. Two females produced only normal embryos and poults (total of 12). One • of the other females had 5 normal poults and embryos and 1 chondrodystrophic embryo. The remaining female produced 7 normal and 2 chondrodystrophic individuals. The chondrodystrophic embryos were similar to those described previously except all had the normal number of phalanges. None of the chondrodystrophic embryos were alive at observation. In the offspring of the 2 females which produced the chondrodystrophic embryos, the ratio was 13 normal to 3 chondrodystrophic suggesting a recessive gene.
579
580
NESTOR REFERENCES
Asmundson, V. S., 1942. An inherited micromelia in the domestic fowl. J. Heredity 33:328-330. Asmundson, V. S., 1944. Inherited shortening of the long bones in the turkey. J. Heredity 35:295—299. Gaffney, L. J., 1975. Chondrodystrophy: An inherited lethal condition in turkey embryos. J. Heredity
66:339-343. Hays, F. A., 1944. Chondrodystrophy in Rhode Island Reds. Amer. Nat. 7 8 : 5 4 - 5 8 . Lamoreux, W. F., 1942. Hereditary chondrodystrophy in the fowl. J. Heredity 33:275-283. McCartney, M. G., 1964. A randombred control population of turkeys. Poultry Sci. 43:739—749.
Downloaded from http://ps.oxfordjournals.org/ at Purdue University Libraries ADMN on June 19, 2015