STUDIES ON THE LONGEVITY AND 

 MORTALITY OF ENGLISH THOROUGHBRED 



HORSES* 



A. Comfort 



Department of Zoology, University College, London 



The General Stud Book records the year of foaling, and in 

 many cases the year of death or disposal, of the thoroughbred 

 racehorses foaled in Britain since the end of the 18th century. 

 This record has been compiled with careful attention to 

 identity, and is greatly superior in quality and quantity to the 

 other non-human mammalian vital statistics so far examined. 

 The possibility of using it as a source of biological data has 

 been recognized before (e.g. Vitt, 1949) but never fully ex- 

 ploited, chiefly, no doubt, because for most purposes each 

 life history must be individually extracted, and statistical 

 treatment of a large sample is therefore very slow work. 



Since actuarial figures for large mammals are scarce and 

 theoretically important, the Stud Book has been examined 

 to see how far it could be expected to yield useful material for 

 comparative age studies, especially in relation to parental age 

 effects and the inheritance of longevity. Study of parental 

 age effects on lifespan in man is complicated by the high cor- 

 relation between ages of spouses (Sonneborn, 1957); there is 

 no such correlation between ages of sire and dam in horse- 

 breeding, and both mares and stallions commonly remain 

 at stud to advanced ages. One special object of the study was 

 to examine Vitt's (1949) claim that the Stud Book records 

 indicate a large parental age effect on the vigour and longevity 



* The work described in this paper was carried out during the tenure of a 

 Nuffield Research Fellowship in Gerontology. Part of it received a Ciba 

 Foundation Ageing Award in 1958. 



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