44 FEEDS AND FEEDING, ABRIDGED 



present knowledge of the net energy value of feeds is far from com- 

 plete. However, tho many of the values are not exact and final, they 

 are of great value in showing approximately what portions of the 

 food consumed by animals are lost at each step in its progress thru 

 the body, and what part is finally available for growth, fattening, 

 work, or milk production. The marvel is that scientists have been 

 able to go so far in solving these most complicated problems. 



III. Factors Influencing the Nutritive Value of Feeds 



Variations in composition of feeding stuffs. — The figures given in 

 Appendix Table I for the composition of any feed are in most 

 instances averages of all analyses of normal samples of that feed 

 which have been reported by the various stations. It is obviously 

 important to learn what variations from these averages may be 

 expected in the case of samples of a given feed from different sections 

 of the country, grown in different years, or when gathered at different 

 stages of maturity. The composition of a crop may be influenced to 

 a limited extent by the amount of available plant food in the soil on 

 which the crop is grown. Climate and stage of maturity are, how- 

 ever, the most important factors affecting the composition of a given 

 feed. Of the cereals, wheat is the most variable in composition, its 

 protein content being profoundly influenced by climate. While the 

 average crude protein content of wheat from the northern plains 

 states is 13.5 per ct., wheat from the Atlantic states contains only 11.7 

 per ct. and that from the Pacific states but 9.9 per ct. crude protein. 

 Climate has little effect on the chemical composition of corn, providing 

 the crop matures. 



The roughages are even more variable in composition than the 

 cereals, owing to the fact that, besides climate, their composition is 

 influenced by the stage of maturity, the manner of curing, and the 

 moisture content. Analyses of corn fodder and corn stover show a 

 water content ranging from over 50 per ct. in field-cured material in 

 wet seasons down to 10 per ct. or less in arid regions or where cured 

 under cover in a dry season. To show the difference in nutritive 

 value of these extremes it may be stated that corn fodder or stover 

 containing 10 per ct. water will carry 80 per ct. more nutrients per 

 100 lbs. than a sample of the same forage containing 50 per ct. water ! 

 To overcome this error so far as possible, separate averages are given 

 for very dry and for ordinary field-cured samples of these feeds in 

 Appendix Table I. 



When plants are immature a much larger percentage of the dry 

 matter consists of protein than when they are mature. For example, 

 dried alfalfa from plants cut when three inches high may contain over 



