different typical feeding conditions and in order to bring out any pos- 

 sible associative effects it may have with other ingredients, the general 

 plan of experiment as shown in Table 2 was followed. The three rations, 

 beet pulp alone, beet pulp and hay (50-0), and beet pulp, hay, and con- 

 centrate mixture (50-25-25) were fed to each of the four animals. The 

 nutritive value of the hay, fed alone, was determined in a previous 

 experiment with four animals. 



The dried beet pulp used for the experiment was representative of 

 United States production. It came from a plant in the eastern beet sugar 

 section and was from the early part of the 1961 production. The com- 

 position of this dried beet pulp did not differ very much from the com- 

 position of beet pulp as reported by Morrison (4) and Schneider (6) 

 except that it had a little higher crude fiber content. 



The hay used was early cut timothy of high quality as indicated by 

 analysis in Table 1. The concentrate mixture used had a protein con- 

 tent of about 18 percent. The chemical composition of these feeds is 

 shown in Table 1. 



Mineralized salt was available to the animals at all times. They were 

 offered water and fed twice daily. 



Methods Employed 



The method used to study the nutritive value of the different rations 

 is the standard procedure followed in this laboratory. It consists of the 

 following : 



1. Preliminary period. This is the adjustment period of 15-18 days 

 during which the animal becomes accustomed to the kind and amount 

 of feed to be evaluated. The level of nutrition at which the nutritive 

 value is determined is slightly above maintenance. 



2. Collection period. This period lasts 8-10 davs. During this time 

 the feed, feces, and urine are weighed, sampled, and a composite samnle 

 of each is kept for analysis. The feces are frozen solid and the urine 

 is kept in a refrigerator just above freezing. No preservative is used 

 for either the feces or urine. 



3. Heat production measurement on feed. The animal is put in the 

 respiration chamber, fed the same amotint of feed as during the collec- 

 tion period, and its heat and methane production measured. Bv means 

 of an "electric eye" the changes of position of the animal and the time 

 the animal spends standing and lying are recorded. Unless the activitv 

 is adjudged to be normal, the period of measurement is repeated until 

 at least 24 hours of heat production on feed is obtained. 



4. Heat production on fast. The heat production of the animal is 

 measured after it has been fasted for 48 hours. A post-absorptive condi- 

 tion is considered to have been reached when methane ceases to be 

 produced and the respiratory quotient (ratio of carbon dioxide pro- 

 duced to oxygen consumed) is 0.75 or less. At the level of nutrition of 

 this experiment, this is reached at 48 hours after feeding. 



The difference between heat production on feed and heat production 

 on fast is the heat increment of the ration or "work of digestion" as 

 it is called by some. 



