10 May, 1918.] Hereditary Unsoundness in Horses. 289 



A CONTRIBUTION TO THE STUDY OF HEREDITARY 

 UNSOUNDNESS IN HORSES. 



By W. A. N. Rohertson, B.V. 8c., Chief Veterinary Officer. 



During the eleven years in which the Government certification of 

 stallions has been in operation, a total of 7,894 horses has been examined. 

 Of this number, 4,957 were draught horses, and 842, or 16.9 per cent., 

 of these were unsound. 



For the purpose of ascertaining to what extent unsoundness is here- 

 ditary, the pedigree through the sire line of nearly all the draught horses 

 has been tabulated, as shown in the following tables. Draught horses 

 only have been taken for the reason that, from the greater number 

 examined and also rejected, more weight can be given to deductions 

 drawn. The tables show all the generations in their proper relation to 

 one another from the foundation member, which member may, and in 

 most cases does, represent a horse that has never been in Australia. 



I have said that nearly all the pedigrees of the draught horses 

 have been tabulated. Approximately 500 have not been included, 

 for the reason that their full pedigree cannot be obtained. Owners 

 have been written to, and old-established newspapers and records 

 have been searched for information, but without avail. The policy 

 has been not to include any horse unless the evidence of his breeding 

 was quite clear, and the difficulties encountered here will be recognised 

 when it is known that there are recorded 5 British Oaks, 8 Champions, 

 7 Clansmen, 7 Commanders, 15 Crown Princes, 6 Darnleys, 9 Dread- 

 noughts, 5 Dundonalds, 7 Gallant Lads, 6 King Georges, 10 Lord Clydes, 

 10 Lord Koberts, 10 Prince Alberts, 13 Prince Charlies, 8 Prince of 

 "Wales, 11 Sir Williams, 9 Young Champions, and so on. It is quite, 

 uncommon to meet with a stallion whose name has not been at least 

 duplicated. 



In such circumstances, when only a short pedigree is given, going 

 back, say, for sake of illustration, to Prince Charlie, without any identi- 

 fication as to which of the thirteen Prince Charlies is meant, it has been 

 impossible to tabulate that horse's pedigree. 



The owner of each horse was written to and asked to supply the 

 necessary information. A very large number responded, but no notice 

 has been taken by the owners of quite 500 stallions. Amongst these 

 500 there probably would be about 200 unsound horses, of which infor- 

 mation was sought. It is quite possible that many of the horses referred 

 to in the tables as " Not examined " were, in point of fact, examined, but 

 the evidence is not sufficient to link them together. 



It will be readily apparent that the names of stallions cannot be 

 published. The system that has been adopted is to give a number to the 

 foundation member, 1, 2, 3, &c., and to use decimal points for the subse- 

 quent generations, 1.1, 1.2, 1.3 representing the first, second, and third 

 son of 1 respectively. This arrangement does not refer to order of birth, 

 but merely to first, second, or third son recorded, and so on. Another 

 figure is used in the next generation, 1.39 representing the ninth recorded 

 son of the third recorded son of the founder 1. When over nine sons are 

 dealt with, the cypher is used in front of the unit of that generation, 

 and represents 9, thus 1.04 is the thirteenth, and 1.0004 is the thirty- 

 first (9-)-9-j-9-|-4). Each of these refers to the first generation; the 



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