Investigations Concerning the Horse. 255 



Either of two methods may be employed in determining the true 

 maintenance ration for the horse : 



(1) Gradually increasing amounts of a given feed are supplied 

 during successive periods, in each of which the maximum amount 

 of work the horse can perform on the allowance and still maintain 

 his weight is ascertained. Thereby the nutrients required for the 

 performance of a given amount of work are found. By substract- 

 ing the nutrients expended in the work done during any period 

 from the total nutrients supplied in that period, the net mainte- 

 nance requirement is determined. 



(2) The horse at rest is first insufficiently fed as shown by a de- 

 creasing body weight. Then after a time the supply of nutrients 

 is gradually increased until bare body equilibrium is established. 



Using the latter method, Grandeau and Leclerc 1 were able to 

 maintain the weight of 3 horses getting walking exercise for half 

 an hour daily on a ration of 17.6 Ibs. of meadow hay, which supplied 

 6.1 Ibs. of digestible nutrients, or 7 Ibs. per 1000 Ibs. live weight. 



Using the first method, Zuntz 2 and his colleagues found the aver- 

 age maintenance requirements of the 1100-lb. horse to be as fol- 

 lows : 



Lbs. Therms* 



Digestible nutrients required to warm the body 7. 06 12. 7 



Nutrients required for the upkeep of the body, finally 



changed into heat 2.43 4.4 



Digestible nutrients needed to furnish the remainder 

 of heat necessary to warm the body, by difference .4.63 8. 3 



* In this table 1 Ib. digestible nutrients, including fat multiplied by 2.4, 

 equals 1.8 therms. Scientists have disagreed as to the relative fuel value of 

 fats and carbohydrates. Zuntz in his work assigns to fat 2.4 times the fuel 

 value of the carbohydrates. It is now generally held that the factor should 

 be 2.25, which factor is used elsewhere in this book. 

 i^ 



By this method it is shown that to maintain the ^ weight of the 

 1100-lb. horse when doing no work required a ration containing 7.06 

 Ibs. of digestible nutrients. This is the amount of food fuel re- 

 quired to properly warm the body. Of this amount 2.43 Ibs. was 

 used in the internal work of the body and in repairing the body 

 tissues, ^exclusive of the energy expended in masticating and di- 

 gesting the ration, and hqfcce was jc equirgd in the form of net 

 nutrients. ("70) ^, Nutrients so consumed, ar.e ultimately/ ^Rjverted 

 into he^tt^mh4^us hei^to V a "tjie body. Subtracting 2.4 Ibs. 



1 Warington, London Live Stock Journal, 1894, p. 9. 



2 Land. Jahrb., 27, 1898, Sup. Ill, pp. 422-426. 



