CONTENTS 



PAGE 



Study of methods of conducting feeding experiments 213 



The practical feeding trial, its limitations and its value 213 



Factors to be considered in planning a feeding experiment 214 



Controllable factors 215 



Uncontrollable factors 215 



Variable factors with special reference to milk production 215 



Methods of conducting feeding experiments with milch cows. ... 217 



The alternation system 217 



The continuous system 2 18 



The combined continuous and alternation system 218 



Relative merits of the three systems 219 



Considerations in grouping experimental animals 220 



Summary - 221 



Statistical study of variation in milk production 222 



Object and methods 222 



Studies of Holstein records: cows in uniform stage of lactation. . 224 



Individual variation 225 



Group variation 226 



Variation in groups of unselected individuals 226 



Variation in groups of individuals of equal production . . 227 



Age of cows as affecting variability 229 



Allowable range in selecting groups of equal production 229 



Size of group as affecting variability 230 



Selection of groups on the basis of production during 



the preceding lactation period 231 



Variation of groups in fat production 232 



Studies of Holstein records: cows in various stages of lactation 232 



Individual variation 232 



Fixed limits versus percentage limits in selecting individ- 

 uals on the basis of equal production 234 



Allowable range in selecting individuals of equal pro- 

 duction 235 



Group variation • 236 



Effect of including aborting cows 236 



Studies of Jersey records: cows in uniform stage of lactation. . 238 



Individual variation 238 



Group variation 238 



Effect of age on the production of dairy cows 239 



Summary 245 



Application of results of statistical study 245 



Bibliography 248 



21 321 



