328 Journal of Agriculture. [10 May, 1910. 



HEREDITARY UNSOUNDNESS IN HORSES. 



jS'oTES ON Evidence as to the Hereditary Character of Certain 

 Pathological Conditions Constituting Unsoundness in Horses 

 (Principally Ossification of the Lateral Cartilages — Sidebone) 

 Furnished by Examination of 2,636 Cases. '^' 



S. S. Cameron. M.R.C.Y.S., {Lond.). n.V.Sc, (Mclb.). 



Present Lack of Recorded Evidence. 



Ossification of the lateral cartilages of the foot of the horse, commonly 

 known as " Sidebone," has been somewhat indefinitely classified as an 

 " hereditary unsoundness " by various writers during the last half century. 

 On the other hand, perhaps the majority of breeders and a i:iumljer of 

 authors have strenuously denied the influence of heredity as a casual factor, 

 alleging that the ossification developed as a result of external injury or the 

 une(jual incidence of concussion brought about by the use of calkin shoes. 

 Arguments, and experience of isolated instances, have been relied on by 

 both sides, and no definite proof has been given whereby the doubts of the 

 contenders might be set at rest. It does not seem to have been realized 

 that the controversy was one capable of settlement by observation and record 

 of the occurrence or otherwise of sidebone in the progeny of side-boned 

 •or sound parents throughout a series of generations in different families 

 of horses; or perhaps if it was so realized, the opportunity for making 

 such observations and records has not been presented in most countries. At 

 all events no such observations have been recorded. 



As late as twenty years ago, when the British Royal Shire Horse 

 Society was contemplating the introduction of compulsory veterinary 

 examination at its annual show, the question of the unsoundnesses to be 

 classed as " hereditary "' was remitted to a Committee of the Council of 

 the Royal College of Veterinary Surgeons. No definite records being 

 available, the Committee included sidebone amongst the unsoundnesses 

 "considered" to be hereditary. Since then, the same lack of definite 

 records is apparent, and I have not been able to unearth any statistics 

 relating to the subject. Even modern authors have been content to repeat 

 the "general idea" as to the hereditary character of Sidebone without 

 furnishing evidence of records of examination. As instancing the un- 

 satisfactory character of the evidence available on the point, the following 

 quotations from present day standard authors may be adduced : — 



Williams {Principles and Practice of Veterinary Surgery) : — 



It is generally admitted that the predisposition to sidebone is hereditary, and many 

 breeders of the best class of cart horses, being aware of the fact, are careful not to 

 breed from an animal with them. 



Hayes (Veterinary Notes — 7th edition, 1906, page 280) : — 



Hereditary predisposition is well marked in this disease. 



RiEEKS {Diseases of the Foot of the Horse, 1906 ; pages 365, 369, 



370):— 



Sidebone constitutes one of the recognised hereditary diseases. Is sidebone 

 hereditary? We can best answer that by saving that some several years ago the 

 <"ouncil of the Roval College of Veterinary Surgeons, at the request of the Royal 



* One of four contributions to a Thesis presented to the University of Melbourne 

 for the degree of Uoclor of Veterinary Science, November, 1909. 



