262 Feeds and Feedi7ig. 



Feeds containing much fiber, such as hay and straw, furnish cor- 

 respondingly less net food for the production of external work. The 

 table shows that masticating and digesting wheat straw requires 

 more energy than the straw supplies. Hence the table shows a neg- 

 ative value of — 100.3 ft.-tons for 1 lb. of wheat straw. However, so 

 long as the work of masticating and digesting a ration containing 

 straw does not altogether consume more energy than is necessary to 

 furnish sufficient heat to warm the body, the straw in such a ration 

 has a positive value corresponding to its content of digestible nutri- 

 ents. On the other hand, when the energy used in masticating and 

 digesting a ration containing straw furnishes more heat than the 

 body needs, then the energy of the straw is wasted and its pres- 

 ence in the ration may be deleterious. This helps to explain why 

 straw is useful in the ration of horses doing light or slow work and is 

 of no value or even detrimental in the ration of horses at rapid or 

 hard work. 



404. Computing' rations. — Two examples are here presented 

 showing the manner in which rations may be computed from the 

 preceding data: 



(1) A maintenance ration. — The amount of meadow hay required 

 to maintain the 1100-lb. horse when at rest is thus calculated: 



7.06 lbs, diges. nutr. required for maintenance (393) _ -. g -. y^c amount of 

 0.391 lb. diges. nutr. in 1 lb. meadow hay (403) 'j^^^y required. 



It has been shown that the maintenance ration must contain at 

 least 2.43 lbs. of net nutrients. (393) Since 1 lb. of the hay fur- 

 nishes 0.182 lb. of net nutrients, (403) 18.1 lbs. of hay will furnish 

 0.182 times 18.1 lbs., or 3.3 lbs. The ration of 18.1 lbs. of hay will 

 thus furnish net nutrients somewhat in excess of the minimum re- 

 quirement. As shown before, this amount of hay is necessary, how- 

 ever, to warm the body. 



{2) A work ration. — If an 1100-lb. farm horse is required to haul 

 a load of 1 ton 20 miles per day on a level road at a speed of 2.9 

 miles per hour, the average draft being 100 lbs., the work performed 

 will be: 



100 (lbs. draft) x 5,280 (ft. per mile) x 10 (miles) = 10,560,000 ft.-lbs. = 5,280 

 ft.-tons. 



During each day the horse will thus perform 5,280 ft.-tons of draft 

 in hauling 1 ton 20 miles. Accordingly, for locomotion, draft, and 



