278 



EXPERIMENT STATION RECORD. 



percentage of unsaturated acids (iodin iniiiilxir) and the total insoluble acids. 

 The acid number and Valenta test wt'ic also increased. The oil did not notice- 

 ably change the melting point of the fat as measured by the Wiley test; it 

 increased somewhat tbe refi'active index. 



"The oil caust'd a marked softness of the l)ntter ; the latter also contained 

 some 2 per cent more moistnre than did the butter produced by the normal 

 ration. No other changes were observed." 



On inheritance in the production of butter fat, II. T>. Rtetz iliiometrika, 

 7 (WOi)), Xo. 1-2, piK J()()-U6). — This is a statistical investigation of inheri- 

 tance in the production of butter fat made from data in Vols. 11-18 of the Ad- 

 vanced Register of the IIolstein-Friesian Association of America. Vols. 1-10 

 were not used because they gave very few pairs of variates that satisfied the 

 conditions. The piii)er is a i»ioneer study of this important side of cattle breed- 

 ing and is of much interest theoretically because allowance has to be made for 

 double selection, since only cows with a certain mininnnn of butter fat pro- 

 duction are admitted to the record. Correlation tables are given and the results, 

 which are discussed in detail, are summarized as follows : 



" The correlation of age and production of butter fat by cows under 4.75 years 

 is approximately two-thirds, and the regression is linear. The correlation of 

 age and production of cows over 4.75 years is substantially zero. The coefficient 

 of variability in production increases gradually from youth to 3 years old, and 

 then decreases to maturity. Production of butter fat is a function transmitted 

 to a marked extent. The coefiicient of heredity between cows and dams in the 

 performance of this function is probably at least as large as the coefficient of 

 mean parental inheritance of physical characters in man. Inheritance in pro- 

 duction is more pronounced in mature than in immature cows. A comparison 

 of the results corrected for selection with the uncorrected values illustrated the 

 great influence of selection in modifying the correlation coefficient." 



The correlation coefficient for cows under 4.75 years old is 0.662±0.007 ; for 

 cows over 4.75 years it is 0.030i!=0.016. If the 15 most extreme variates are 

 excluded the correlation coefficient is 0.004±0.026. By including older cows the 

 correlation coefficient is 0.688±0.006, a slight increase, while the regression of 

 production on age is decreased. For the group under 4.75 years the regression 

 of production on age is 1.901±0.021 ; for the group under 5.25 years, 1.819± 

 0.018. The mean, standard deviation, coefficient of variation, and coefficient of 

 correlation are given in the following table : 



Mean, staiiditnl deviation, coefficient of varialyilitji. and coefficient of correlation 

 "f offspring, dams, and (jranddams. 



Relationship of animals. 



Offspring and dams (Offspring 



under 4 years \Dams 



Offspring and dams ^Offspring 



over 4 years \Dams 



Offspring and dams )o«snrinir 

 differing by less [nMms "'■■ 

 thanl vear uams 



Granddams and off- |^(*™^ 



spring 



t ern a 1 

 granddams. 



10.687 + 0.057 

 10.605 + 0.057 

 15.316 + 0.070 

 15.368 + 0.070 



12.913 + 0.063 

 12.915+0.063 



15. 383 + 0. 073 

 15. 423 ±0.077 



Standard de- 

 viation. 



2.136 + 0.040 

 2.141 + 0.040 

 2.543 + 0.049 

 2.646±0.051 



3. 292 J 

 3.380d 



0.045 

 0.046 



2.377 + 0.052 

 2. 495±0. 055 



Coeflieient of 

 variability. 



19.99+0.38 

 20.19 + 0.38 

 16.60 + 0.33 

 17.22 + 0.34 



25.46 + 0.36 

 26.17 + 0.38 



Coefficient cor- 

 relation. 



\ 0.344 + 0.023 



I 0.28^ ±0.025 



I 0.(551 ±0.011 



i 0.301 ±0.028 



The correlation of milk fat production with the production by dams of sires 

 mated to the cows was 0.140±0.025. Multiple correlations showed that a few 

 paternal granddams selected for fancy points affected the correlation coefficient 



