BULLETIN 291 



THE CORRELATION BETWEEN THE BUTTER-FAT 

 PERCENTAGE OF ONE LACTATION AND THE 

 BUTTER-FAT PERCENTAGE OF SUCCEED- 

 ING LACTATIONS IN JERSEY CATTLE* 



By John W. Gowen. 



SUMMARY 



This bulletin presents a study of the accuracy with which 

 the butter-fat percentage of one lactation predicts the butter- 

 fat percentage of a subsequent lactation for a pure bred herd 

 of Jerseys under uniform farm conditions. The correlation 

 coefficients describing this relation range from +0.6781 ±.0310 

 to -f 0.2470 ±.0640. The numerical value of these correlation 

 coefficients signifies that with a fair degree of accuracy the bat- 

 ter-fat percentage of one lactation measures the probable butter- 

 fat percentage of a subsequent lactation. 



The mean of these correlation coefficients for butter-fat 

 percentage of one lactation with another was +0.5215. The 

 mean of the milk production of one lactation with another was 

 +0.5352. There is consequently no difference in the relative 

 accuracy of the prediction of milk yield or butter-fat percentage 

 from one lactation to another. 



The mean value of the correlation coefficients for the 

 monthly egg yield of White Leghorn pullets with their year 

 egg yield was +0.446. Comparison of this correlation with 

 those given above makes it seem that greater dependence may 

 be placed in the record for milk yield or butter-fat percentage 

 of a cow as a measure of future production than can be placed 



*This paper is an abstract of a longer paper on "Studies in Milk 

 Secretion VI. On the Variations and Correlations of Butter-Fat Per- 

 centage with Age igi Jersey Cattle," published by the same author in 

 Genetic, May 1920. All literature citations should be made to this com- 

 plete paper. 



