BULLETIN 289 



THE CORRELATION BETWEEN MILK YIELD OF ONE 



LACTATION AND THAT OF SUCCEEDING 



LACTATIONS.* 



By John W. Gowen. 



SUMMARY 



This bulletin presents a study of the accuracy with which 

 the milk production of one lactation indicates the milk produc- 

 tion of a subsequent lactation for a pure bred herd of Jerseys 

 under uniform farm conditions. The correlations describing the 

 relation of one lactation with another lactation range from 

 -(-0.7306 to +0.2 144. The numerical value of such correlation 

 coefficients signifies that with a fair degree of accuracy the milk 

 production of one lactation measures the probable milk produc- 

 tion of a subsequent lactation. 



The arithmetical equations necessary to determine this 

 probable production are given in table 3. 



The relation of the milk production of one lactation with 

 the milk production over five lactations is determined. These 

 correlation coefficients range from -(-0.8613±.0186 to 0.7416 

 ±.0323. Such high values indicate that with slight inaccuracy 

 the milk production of one lactation predicts the milk produc- 

 tion for the first five lactations. 



Data are presented to show that the milk production of one 

 lactation is a better measure of a cow's milk production of an- 

 other lactation than the egg production of one month is of the 

 egg production for the year. 



Table 5 furnishes a ready means of determining from the 

 milk yield of the first lactation (8 months of lactation) what 



*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 in Jersey Cattle" by the same author published in 

 Genetics, March 1920. All literature citations should be made to this 

 complete paper. 



