Lifespan of Cattle and Horses 65 



from Luneberg, 3 years, 4 months; from East Friesland, 3 

 years, 4 months. He concludes from this low age of death 

 that the premature culling of bulls is due more to private and 

 economic reasons than to the proper physiological limit of 

 productivity of the individual animals. Hartwig (1959, un- 

 published) examined the average age at death of 2,000 herd- 

 book bulls from Saxony-Anhalt. An average age of 4 years, 9 

 months was noted; 83-5 per cent of the animals had been 

 killed because they were no longer used for covering. The 

 reasons for this were principally economic, as Hogreve had 

 also found. Schroder (1958) found a higher average age of 5 

 years, 4 months among suppressed bulls kept for fertilization. 

 In insemination stations we find that the bulls are kept by 

 means of better utilization of breed and better conditions 

 so that the animals in general grow older. Schroder found 19 

 bulls which were older than 10 years. The most important 

 causes of death of the bulls were : 



culled for genetic reasons 60 bulls = 20-27 per cent 



diseases of the genital system 59 ,, =19*9 ,, ,, 



tuberculosis 58 ,, =19-5 ,, ,, 



diseases of the legs 33 ,, =11*1 ,, ,, 



Five per cent of the bulls were slaughtered after swallowing 

 foreign bodies and 2 per cent because of viciousness. Here 

 again economic aspects play the leading part, so that these 

 factors make the determination of a real average age impos- 

 sible. Cows and bulls can both reach 18 or 20 years of age, 

 though these figures are exceptional. 



Horses 



It is very difficult to make corresponding observations on 

 the regional breeding of horses, therefore these studies were 

 carried out on stallions that were kept as long as they con- 

 tinued to breed. For that reason a better estimate of their 

 real age at death can be made. Research along this line has 

 been undertaken on stallions in the district stud of Kreuz by 



AGEING— V — 3 



