FEEDING HORSES AND MULES 279 
time; but for horses working at ordinary pace only a relatively 
small protein supply is required. The amounts of non-nitrogenous 
components of the ration, on the other hand, must be increased 
with the amount of work done. The standards for work horses, 
therefore, call for a relatively wide nutritive ratio of 1:6 or 1:7; 
even this ratio is narrower than that of rations ordinarily fed in 
this country, unless alfalfa or clover hay is fed, in which case a 
considerably narrower ratio is fed. Horses in the eastern and 
northern States are frequently given no other feeds than timothy 
hay and either oats or corn and oats. The nutritive ratios of these 
feeds are as follows: Timothy hay, 1:16; corn, 1: 9.5, and oats, 
1:5.5. It is evident, therefore, that rations composed of these feeds 
will be likely to have nutritive ratios of 1:9 or wider. American 
horses (outside of alfalfa sections) are rarely fed appreciable 
quantities of high-protein feeds, showing that they require but 
relatively small amounts of protein in their feed, and that they 
receive wide nutritive ratios even when at hard work. 
Measurement of Work.—The amount of work done by a horse 
may be measured by one of the usual units of mechanical energy, a 
foot-pound or a foot-ton. A foot-pound is the amount of energy ex- 
pended in raising one pound one foot high; a foot-ton is that 
expended in raising one ton one foot high. The horse-power is 
another common unit of energy, and is equivalent to 550 foot- 
pounds per second, or nearly 2,000,000 foot-pounds per hour. A 
horse’s capacity for continuous work is, however, considerably smaller 
‘than this amount, and may be put at about 1,000,000 foot-pounds 
per hour per 1000 pounds weight. Light work done by horses, as 
commonly understood, will mean from 500,000 to 1,000,000 foot- 
pounds per hour, medium work from 1,000,000 to 1,500,000, and 
heavy work from 1,500,000 ‘to 2,000,000 foot-pounds.? Instead of 
measuring the amount of work done by units of mechanical energy, 
this may be measured in the same way as the potential energy of 
feeds, by the unit of heat, a Calorie or a therm (p. 45); this is a 
convenient method, because these unit values are now often used in 
feed analyses and in statements of feeding standards. One Calorie 
corresponds very closely to 1.54 foot-tons or 3087 foot-pounds. 
The relation of the nutrients required for the production of a 
certain work by the horse under varying conditions has been studied 
in extensive investigations by German and French scientists, espe- 
cially among the former, by Wolff, Zuntz, and Kellner. These 
*Murray, “Chemistry of Cattle Feeding,” p. 153, 
