6 CONTENTS. 



Page. 



Factors affecting the energy requirement 64 



Muscular activity 65 



Minor muscular motions 65 



Lying and standing 66 



Individuality 66 



Condition 67 



Age 68 



External temperature 69 



Regulation of body temperature 69 



Critical temperature 71 



Feed consumption a source of heat 71 



Isodynamic replacement 72 



Relation of maintenance ration to critical temperature 72 



Feed consumption lowers the critical temperature 73 



Critical temperature for farm animals 73 



The protein requirement for maintenance 74 



Protein katabolized during fasting 74 



Influence of previous feed 74 



Fasting katabolism variable 74 



The minimum of protein 75 



Influence of nonnitrogenous materials 76 



Relation to fasting katabolism 76 



Effect of surplus of protein 78 



Increases protein katabolism 78 



Utilization of protein limited 80 



Protein as a source of energy 81 



Storage of protein 82 



Fluctuations in body protein 83 



Relation to energy supply 84 



Value of nonprotein 88 



Minimum of protein for farm animals 89 



Cattle 89 



Sheep 94 



Swine 96 



The horse 97 



The optimum of protein 97 



Relative values of proteins 99 



Differences in constitution of proteins 99 



Absence of certain constituents 100 



Proportions of constituents 101 



Experimental methods 102 



Michaud's investigations 102 



Zisterer's experiments 104 



Results are qualitative 105 



Thomas's experiments 106 



Significance of results 108 



ILLUSTRATION. 



Page. 



Figure 1. — Availability of metabolizable energy of hay 35 



