Post by Cascade Meadows Farm - Kirk on Jan 8, 2018 15:37:10 GMT -5
Chondrodysplasia Facts
1.Chondrodysplasia is a disease of the cartilage and bone. Chondrodysplasia simply means “cartilage deformity”.
Chondro = Cartilage
Dysplasia = Deformity
2. There are many different causes of chondrodysplasia. Most causes are genetic, and are due to defective (broken) genes whose original purpose was to help build normal cartilage and bone.
3. All animals that have cartilage and bone are subject to having chondrodysplasia when genes involved in forming cartilage are broken (due to copy errors). Chondrodysplasia has been found in mice, rats, cats, dogs, pigs, horses, chickens, humans, and cattle and many other animals.
4. One of the critical genes involved in forming normal healthy cartilage is the ACAN gene, which produces a critical protein called aggrecan. All animals and humans require two good working ACAN genes in order to have enough aggrecan to build healthy normal cartilage. One good working ACAN gene is not enough.
5. Aggrecan protein performs two critical roles: a. it is a critical element of the extra-cellular matrix (ECM) and b. it is a critical element of cartilage and joints.
6. Animal bodies are made from a mass of cells structured and held together by the Extra-Cellular Matrix (ECM). Cells produce and exude substances that connect one cell with other cells which form a matrix to build the animal’s form. Aggrecan is an important part of the ECM.
7. In fetal development, an animal’s skeleton is first constructed from cartilage. Then, much of that cartilage is ossified into bone… except the ends of bone remain as cartilage, to form well-cushioned, smooth-gliding joints. Aggrecan in its role of ECM, helps structure the matrix framework for normal cartilage and bones. Aggrecan in its role as an important cartilage compound, provides superior cushioning for long-lasting and easily gliding joints. These functional abilities are dependent on a high aggrecan concentration, provided by two normal functioning ACAN genes, one from each parent. Animals without two good working ACAN genes, are deformed.
8. If one of an animal’s two ACAN genes is broken, the animal is stunted by aggrecan deficiency causing a deformed extra-cellular matrix, and and causing deformed cartilage and shortened bones. If both ACAN genes are broken, the baby will have very, very short bones, especially legs--maybe three inches instead of 16, spine maybe 10 inches instead of 23. Skull is actually larger than normal, and rounded, not small and pear shaped as found in normal skulls. Sometimes, for known (as yet) reasons, the skin doesn't always fully form either and the effect is the same as an open hernia. The horribly deformed calf dies at birth (often prematurely), and sometimes kills the mother. What makes it hard to calve out is the guts are normal size, and they act like a bean bag, and can't be pushed out.
9. Any gene that is essential for life, is called an “Essential Gene”. When essential genes are broken, they are called “Lethal Genes”. ACAN genes are essential genes. A broken ACAN gene (responsible for chondrodysplasia in Dexters) , is a lethal gene.
10. The types of chondrodysplasia caused by broken ACAN genes, are dominant type genes. The term “carrier” is highly inaccurate with these dominant genes. “Carrier” means that an animal carries a gene, but does not express that gene. A broken ACAN gene always results in aggrecan deficiency (causing chondrodysplasia). It is always expressed, and never “carried”. A Dexter with a tested chondrodysplasia gene (BD1 or BD2) doesn't “carry” chondrodysplasia…. It HAS chondrodysplasia, a disease of the cartilage.
11. Some genetic forms of chondrodysplasia (not yet reported in Dexters but found in other cattle), are recessive. An animal CAN “carry” those recessive forms of chondrodysplasia without showing any effects.
12. Two forms of testable broken ACAN genes have been found in the Dexter breed so far. Geneticists label them as BD1 and BD2. BD stands for bulldog, because the deformed calves resemble bulldogs. BD1 and BD2 are lethal genes. They are very similar to each other, and both are a dominant form. They cannot be “carried” because they aren't recessive. An animal with these genes HAS chondrodysplasia (deformed cartilage). While homozygous BD1 chondrodysplasia calves most often die at 7-9 months gestation, homozygous BD2 chondrodysplasia calves typically die at around 2 months gestation according to some breeders.
13. A deficiency of aggrecan, due to a broken ACAN gene, causes bones and cartilage and joints to be malformed and lack cushioning. This can lead to an abnormal gait, and causes wear and tear on bone ends, making joints wear-out sooner than normal, leading to arthritis sooner than they otherwise would have. This can reduce a Dexter's healthy life by up to 50%.
14. Some chondrodysplastic steers slaughtered at two years of age, can already show signs of joint problems, when joints are examined. Aggrecan deficiency caused by broken ACAN genes can cause early osteoarthritis, and osteochondrosis/osteochondritis dissecans.
15. A broken ACAN gene (chondrodysplasia) has no effect on temperament or hardiness… but an animal with a mobility disability caused by the broken gene, can move slower, sometimes making them appear calm, but it's not true genetic calmness. The BD1 and BD2 defective ACAN genes do not bestow any special attributes to cattle, other than defective cartilage and bone. Short, compact cattle have tons of benefits including the ability to gain fat easier, and greater safety, but all those benefits can be had in naturally short cattle without cartilage and bone diseases.
16. All species and breeds of animals are subject to various forms of chondrodysplasia and other forms of dwarfism defects because genes are miscopied (broken) from time to time causing dwarfism defects. In larger breeds, the dwarfism defects stand out and are easily culled. In smaller breeds, dwarfism defects can hide more easily.
17. In the 1930’s, 40’s, and 50’s, there was a huge trend toward selecting much smaller frame sizes in Angus, Hereford, and a few other breeds. Breeders selected their shortest bulls and they were worth large sums of money. In some cases these short bulls had dwarfism defects which they spread to their offspring. Dwarfism defects were unwelcomed intruders. When the Angus and Hereford breeders found out about the defects, the value of their cattle plummeted, and they started culling the animals with the defect genes. Many of the shorter animals were naturally short without dwarfism defects.
18. Dexters were never meant to have chondrodysplasia as part of the breed. The early breed descriptions and breed standards describe Dexters as true-breeding short and beefy cattle where 100% of individuals have shorter legs and thick beefy bodies. No mention of the three different phenotypes associated with BD1 or BD2 chondrodysplasia appears in any early breed standards. It's very possible that fewer than 1% of the original Dexters had the chondrodysplasia defect.
19. BD1 and BD2 chondrodysplasia, found in a very small minority of today's Dexters, can only exist in a heterozygous form, because it's lethal when it's homozygous. That means that chondrodysplastic-dexters are hybrids and can't breed true. They throw three different genotypes, and three different phenotypes:
Homozygous Normal = two good working ACAN genes, no chondrodysplasia genes, normal cattle.
Heterozygous Chondrodysplasia = one normal ACAN gene and one defective ACAN gene resulting in aggrecan deficiency and defective cartilage.
Homozygous Chondrodysplasia = two defective ACAN genes, total lack of aggrecan, lethal deformity, dead deformed calves, often aborted at 7-8 months, and sometimes killing the mother if they go full-term.
20. The chondrodysplasia disease artificially alters the proportions of an animal, hiding their true genetic size and proportions. When you view an animal with chondrodysplasia, the size and proportions are due to the aggrecan deficiency genetic disease, starving the animal of a critical protein. Aggrecan deficiency caused by one broken ACAN gene, artificially shrinks the height of cattle by 4-9 inches.
21. In some cases, the disease-altered proportions of chondrodysplastic cattle can be appealing to show judges who appreciate shorter legged stock. But the original purpose of livestock shows was to identify animals that had good breeding merit. Chondrodysplastic animals can't breed true for their dimensions because they are lethal-gene hybrids. A show-winning chondrodysplastic animal can't breed true. Further, the judge can't see the cartilage deformity problems inside the joints of the animal.
22. Cattle with chondrodysplasia require extra work and special handling.
23. Every calf born to a chondrodysplastic parent must be DNA tested generation after generation after generation… there is no end to this testing. Herds that have eliminated chondrodysplasia, never need to test for chondrodysplasia ever again.
24. Female chondrodysplastic animals have shrunken frames that can have difficulties delivering normal sized calves. 50% of their calves will be normal, non-chondrodysplasia calves, and their normal size could pose a risk to the dwarf mother.
25. Animals with chondrodysplasia defects have weak joints that require special management. Allowing animals with chondrodysplasia to run with normal animals, can lead to worn out joints and early arthritis problems. Many breeders keep their chondrodysplastic Dexters with weak joints, separated from their normal healthy Dexters.
26. Male and female chondrodysplastic Dexters must be kept separated from each other to keep them from breeding together and producing highly deformed dead calves. If allowed to breed with each other, 25% of calves will be born horribly disfigured and dead.
27. If you have any chondrodysplasia genes on your farm, it takes a ton of effort and is nearly impossible to keep two chondrodysplastic animals from breeding together in the long run. Chondrodysplastic bulls can jump fences. Chondrodysplastic bulls can breed their young chondrodysplastic daughters at very young ages. Young chondrodysplastic bull calves at very young ages, can breed their chondrodysplastic mothers.
28. No official Dexter standards prior to the 1990’s, made any mention of chondrodysplasia being a desired trait. Instead, the old standards described a breed of true-breeding short cattle all of one type, with no deformities. Chondrodysplasia is a modern addition to the breed.
29. The early professors who studied Dexters and wrote papers about them, never mentioned chondrodysplasia nor its effects (likely because the vast majority of Dexters were true shorts, without chondrodysplasia). Professor Low in the 1840’s described Dexters as a typical beef-framed breed with every animal having a short beefy frame and made no mention of dead calves. Professor Wilson in 1908 stated that Dexters were the likely result of a cross between black dairyish Kerry cattle with longer legs, and red Devon beef cattle with naturally short legs (non-chondrodysplasia).
30. Many various genes affect the leg length and size of cattle. Short legs and long legs can be the effect of many other normal genes, not related to chondrodysplasia. Herds tested free of chondrodysplasia can still have both long legged and short legged individuals.
31. Many untested “short-legged” Dexters, assumed to have chondrodysplasia, do not have chondrodysplasia. They are just naturally short, without the chondrodysplasia defect.
32. The terms “Shorty” or “Short” or “Short-Legged” means that the animal is shorter than average. A short Dexter may simply be naturally short, or it may have the chondrodysplasia defect caused by a BD1 or BD2 defect gene. Only DNA testing can tell you for certain.
33. Chondrodysplasia interferes with the ability of breeders to select for consistent true-breeding Dexters that consistently throw short and thick calves 100% of the time, as described by the early breed standards. Many chondrodysplastic herds consist of oversized non-chondro Dexters, along with shorter Dexters with the chondrodysplasia cartilage defect hiding their true larger genetics. It's impossible to stabilize a herd based on chondrodysplasia, because chondrodysplasia hides the true height genetics of the animals.
34. Small, friendly short-legged Dexters, tested free of Chondrodysplasia, can freely breed together, producing an entire consistent herd of trouble-free, compact, short and friendly, healthy, long-lived Dexters, with normal healthy cartilage and joints.
35. Most all Dexter breed associations do not require testing for the chondrodysplasia defect for registration, so it's buyer-beware. The Dexter Cattle Society (DCS) in the UK has recently added the requirement to test males only, but not females. Buyers should ask to see DNA test evidence of the animal’s chondrodysplasia status, before buying.
36. The genetics testing labs have been reporting BD1 and BD2 chondrodyplasia test results using wrong terms and misinformation. They report BD1 and BD2 the same way they report fully recessive genes and that is a error that needs to be corrected. BD1 and BD2 Chondrodyplasia are semi-dominant (not recessive). The labs should be reporting the three different related genotypes and phenotypes:
No Mutated Genes = Normal, not affected.
One Mutated Gene = Affected with abnormal cartilage and bone, likely poor joints and likely early arthritis
Two Mutated Genes = Severely Affected cartilage and bone, severely deformed, lethal at birth
1.Chondrodysplasia is a disease of the cartilage and bone. Chondrodysplasia simply means “cartilage deformity”.
Chondro = Cartilage
Dysplasia = Deformity
2. There are many different causes of chondrodysplasia. Most causes are genetic, and are due to defective (broken) genes whose original purpose was to help build normal cartilage and bone.
3. All animals that have cartilage and bone are subject to having chondrodysplasia when genes involved in forming cartilage are broken (due to copy errors). Chondrodysplasia has been found in mice, rats, cats, dogs, pigs, horses, chickens, humans, and cattle and many other animals.
4. One of the critical genes involved in forming normal healthy cartilage is the ACAN gene, which produces a critical protein called aggrecan. All animals and humans require two good working ACAN genes in order to have enough aggrecan to build healthy normal cartilage. One good working ACAN gene is not enough.
5. Aggrecan protein performs two critical roles: a. it is a critical element of the extra-cellular matrix (ECM) and b. it is a critical element of cartilage and joints.
6. Animal bodies are made from a mass of cells structured and held together by the Extra-Cellular Matrix (ECM). Cells produce and exude substances that connect one cell with other cells which form a matrix to build the animal’s form. Aggrecan is an important part of the ECM.
7. In fetal development, an animal’s skeleton is first constructed from cartilage. Then, much of that cartilage is ossified into bone… except the ends of bone remain as cartilage, to form well-cushioned, smooth-gliding joints. Aggrecan in its role of ECM, helps structure the matrix framework for normal cartilage and bones. Aggrecan in its role as an important cartilage compound, provides superior cushioning for long-lasting and easily gliding joints. These functional abilities are dependent on a high aggrecan concentration, provided by two normal functioning ACAN genes, one from each parent. Animals without two good working ACAN genes, are deformed.
8. If one of an animal’s two ACAN genes is broken, the animal is stunted by aggrecan deficiency causing a deformed extra-cellular matrix, and and causing deformed cartilage and shortened bones. If both ACAN genes are broken, the baby will have very, very short bones, especially legs--maybe three inches instead of 16, spine maybe 10 inches instead of 23. Skull is actually larger than normal, and rounded, not small and pear shaped as found in normal skulls. Sometimes, for known (as yet) reasons, the skin doesn't always fully form either and the effect is the same as an open hernia. The horribly deformed calf dies at birth (often prematurely), and sometimes kills the mother. What makes it hard to calve out is the guts are normal size, and they act like a bean bag, and can't be pushed out.
9. Any gene that is essential for life, is called an “Essential Gene”. When essential genes are broken, they are called “Lethal Genes”. ACAN genes are essential genes. A broken ACAN gene (responsible for chondrodysplasia in Dexters) , is a lethal gene.
10. The types of chondrodysplasia caused by broken ACAN genes, are dominant type genes. The term “carrier” is highly inaccurate with these dominant genes. “Carrier” means that an animal carries a gene, but does not express that gene. A broken ACAN gene always results in aggrecan deficiency (causing chondrodysplasia). It is always expressed, and never “carried”. A Dexter with a tested chondrodysplasia gene (BD1 or BD2) doesn't “carry” chondrodysplasia…. It HAS chondrodysplasia, a disease of the cartilage.
11. Some genetic forms of chondrodysplasia (not yet reported in Dexters but found in other cattle), are recessive. An animal CAN “carry” those recessive forms of chondrodysplasia without showing any effects.
12. Two forms of testable broken ACAN genes have been found in the Dexter breed so far. Geneticists label them as BD1 and BD2. BD stands for bulldog, because the deformed calves resemble bulldogs. BD1 and BD2 are lethal genes. They are very similar to each other, and both are a dominant form. They cannot be “carried” because they aren't recessive. An animal with these genes HAS chondrodysplasia (deformed cartilage). While homozygous BD1 chondrodysplasia calves most often die at 7-9 months gestation, homozygous BD2 chondrodysplasia calves typically die at around 2 months gestation according to some breeders.
13. A deficiency of aggrecan, due to a broken ACAN gene, causes bones and cartilage and joints to be malformed and lack cushioning. This can lead to an abnormal gait, and causes wear and tear on bone ends, making joints wear-out sooner than normal, leading to arthritis sooner than they otherwise would have. This can reduce a Dexter's healthy life by up to 50%.
14. Some chondrodysplastic steers slaughtered at two years of age, can already show signs of joint problems, when joints are examined. Aggrecan deficiency caused by broken ACAN genes can cause early osteoarthritis, and osteochondrosis/osteochondritis dissecans.
15. A broken ACAN gene (chondrodysplasia) has no effect on temperament or hardiness… but an animal with a mobility disability caused by the broken gene, can move slower, sometimes making them appear calm, but it's not true genetic calmness. The BD1 and BD2 defective ACAN genes do not bestow any special attributes to cattle, other than defective cartilage and bone. Short, compact cattle have tons of benefits including the ability to gain fat easier, and greater safety, but all those benefits can be had in naturally short cattle without cartilage and bone diseases.
16. All species and breeds of animals are subject to various forms of chondrodysplasia and other forms of dwarfism defects because genes are miscopied (broken) from time to time causing dwarfism defects. In larger breeds, the dwarfism defects stand out and are easily culled. In smaller breeds, dwarfism defects can hide more easily.
17. In the 1930’s, 40’s, and 50’s, there was a huge trend toward selecting much smaller frame sizes in Angus, Hereford, and a few other breeds. Breeders selected their shortest bulls and they were worth large sums of money. In some cases these short bulls had dwarfism defects which they spread to their offspring. Dwarfism defects were unwelcomed intruders. When the Angus and Hereford breeders found out about the defects, the value of their cattle plummeted, and they started culling the animals with the defect genes. Many of the shorter animals were naturally short without dwarfism defects.
18. Dexters were never meant to have chondrodysplasia as part of the breed. The early breed descriptions and breed standards describe Dexters as true-breeding short and beefy cattle where 100% of individuals have shorter legs and thick beefy bodies. No mention of the three different phenotypes associated with BD1 or BD2 chondrodysplasia appears in any early breed standards. It's very possible that fewer than 1% of the original Dexters had the chondrodysplasia defect.
19. BD1 and BD2 chondrodysplasia, found in a very small minority of today's Dexters, can only exist in a heterozygous form, because it's lethal when it's homozygous. That means that chondrodysplastic-dexters are hybrids and can't breed true. They throw three different genotypes, and three different phenotypes:
Homozygous Normal = two good working ACAN genes, no chondrodysplasia genes, normal cattle.
Heterozygous Chondrodysplasia = one normal ACAN gene and one defective ACAN gene resulting in aggrecan deficiency and defective cartilage.
Homozygous Chondrodysplasia = two defective ACAN genes, total lack of aggrecan, lethal deformity, dead deformed calves, often aborted at 7-8 months, and sometimes killing the mother if they go full-term.
20. The chondrodysplasia disease artificially alters the proportions of an animal, hiding their true genetic size and proportions. When you view an animal with chondrodysplasia, the size and proportions are due to the aggrecan deficiency genetic disease, starving the animal of a critical protein. Aggrecan deficiency caused by one broken ACAN gene, artificially shrinks the height of cattle by 4-9 inches.
21. In some cases, the disease-altered proportions of chondrodysplastic cattle can be appealing to show judges who appreciate shorter legged stock. But the original purpose of livestock shows was to identify animals that had good breeding merit. Chondrodysplastic animals can't breed true for their dimensions because they are lethal-gene hybrids. A show-winning chondrodysplastic animal can't breed true. Further, the judge can't see the cartilage deformity problems inside the joints of the animal.
22. Cattle with chondrodysplasia require extra work and special handling.
23. Every calf born to a chondrodysplastic parent must be DNA tested generation after generation after generation… there is no end to this testing. Herds that have eliminated chondrodysplasia, never need to test for chondrodysplasia ever again.
24. Female chondrodysplastic animals have shrunken frames that can have difficulties delivering normal sized calves. 50% of their calves will be normal, non-chondrodysplasia calves, and their normal size could pose a risk to the dwarf mother.
25. Animals with chondrodysplasia defects have weak joints that require special management. Allowing animals with chondrodysplasia to run with normal animals, can lead to worn out joints and early arthritis problems. Many breeders keep their chondrodysplastic Dexters with weak joints, separated from their normal healthy Dexters.
26. Male and female chondrodysplastic Dexters must be kept separated from each other to keep them from breeding together and producing highly deformed dead calves. If allowed to breed with each other, 25% of calves will be born horribly disfigured and dead.
27. If you have any chondrodysplasia genes on your farm, it takes a ton of effort and is nearly impossible to keep two chondrodysplastic animals from breeding together in the long run. Chondrodysplastic bulls can jump fences. Chondrodysplastic bulls can breed their young chondrodysplastic daughters at very young ages. Young chondrodysplastic bull calves at very young ages, can breed their chondrodysplastic mothers.
28. No official Dexter standards prior to the 1990’s, made any mention of chondrodysplasia being a desired trait. Instead, the old standards described a breed of true-breeding short cattle all of one type, with no deformities. Chondrodysplasia is a modern addition to the breed.
29. The early professors who studied Dexters and wrote papers about them, never mentioned chondrodysplasia nor its effects (likely because the vast majority of Dexters were true shorts, without chondrodysplasia). Professor Low in the 1840’s described Dexters as a typical beef-framed breed with every animal having a short beefy frame and made no mention of dead calves. Professor Wilson in 1908 stated that Dexters were the likely result of a cross between black dairyish Kerry cattle with longer legs, and red Devon beef cattle with naturally short legs (non-chondrodysplasia).
30. Many various genes affect the leg length and size of cattle. Short legs and long legs can be the effect of many other normal genes, not related to chondrodysplasia. Herds tested free of chondrodysplasia can still have both long legged and short legged individuals.
31. Many untested “short-legged” Dexters, assumed to have chondrodysplasia, do not have chondrodysplasia. They are just naturally short, without the chondrodysplasia defect.
32. The terms “Shorty” or “Short” or “Short-Legged” means that the animal is shorter than average. A short Dexter may simply be naturally short, or it may have the chondrodysplasia defect caused by a BD1 or BD2 defect gene. Only DNA testing can tell you for certain.
33. Chondrodysplasia interferes with the ability of breeders to select for consistent true-breeding Dexters that consistently throw short and thick calves 100% of the time, as described by the early breed standards. Many chondrodysplastic herds consist of oversized non-chondro Dexters, along with shorter Dexters with the chondrodysplasia cartilage defect hiding their true larger genetics. It's impossible to stabilize a herd based on chondrodysplasia, because chondrodysplasia hides the true height genetics of the animals.
34. Small, friendly short-legged Dexters, tested free of Chondrodysplasia, can freely breed together, producing an entire consistent herd of trouble-free, compact, short and friendly, healthy, long-lived Dexters, with normal healthy cartilage and joints.
35. Most all Dexter breed associations do not require testing for the chondrodysplasia defect for registration, so it's buyer-beware. The Dexter Cattle Society (DCS) in the UK has recently added the requirement to test males only, but not females. Buyers should ask to see DNA test evidence of the animal’s chondrodysplasia status, before buying.
36. The genetics testing labs have been reporting BD1 and BD2 chondrodyplasia test results using wrong terms and misinformation. They report BD1 and BD2 the same way they report fully recessive genes and that is a error that needs to be corrected. BD1 and BD2 Chondrodyplasia are semi-dominant (not recessive). The labs should be reporting the three different related genotypes and phenotypes:
No Mutated Genes = Normal, not affected.
One Mutated Gene = Affected with abnormal cartilage and bone, likely poor joints and likely early arthritis
Two Mutated Genes = Severely Affected cartilage and bone, severely deformed, lethal at birth
