Types and Market Classes of Live Stock 



495 



The number of horses "not on farms" in the United States declined 

 from 3,183,000 on April 15, 1910, to 1,706,000 on January 1, 1920, as 

 reported by the census. 



Average life of work horse.— The Horse Association of America ^ 

 estimates as a result of its investigations that horses and mules on 

 farms, going into service as three-year-olds, have an average period of 

 service of 12 years. Horses and mules not on farms (horses used in 

 cities and towns, and by lumber men, mine owners, contractors, etc.), 

 going into service as six-year-olds, are estimated to remain in service 

 for an average of 9 years. For all horses and mules that reach working 

 age, the average duration of life is therefore 15 years. The Association 

 also reports that the death rate in young stock "between the time they 



Fig. 192. — Distribution of horses two years old or over in the United States. 



are 6 to 8 months old and the time they are 36 months old, is about 

 5 per cent per year, or a loss of one colt out of each twenty, in their 

 yearling and two-year-old seasons respectively." 



According to these figures, one-twelfth of working animals on 

 farms and one-ninth of working animals not on farms must be replaced 

 annually in order to maintain the total number of work animals in 

 use. Replacement must come from the annual crop of foals. A num- 

 ber of foals are lost before 6 or 8 months of age, and 10 per cent of the 

 remainder die before reaching three years of age. The foal crop of a 

 given year less 10 per cent gives the probable number available at three 

 years of age to replace losses among work animals. Applying this 



1 Leaflet 57, Horse Association of America, Union Stock Yards, Chicago, IH. 



