250 Maine Agricultural Experiment Station. 1919. 



d. Studies in Milk Secretion. VI. On the Variations and 



Correlations of Butter-Fat Percentage with Age in 

 Jersey Cattle. By John W. Gowen. 



e. • Studies in Milk Secretion. VII. Transmitting Quali- 



ties of Jersey Sires for Milk Yield, Butter-Fat Per- 

 centage and Butter. By Raymond Pearl, John W. 

 Gowen and John Rice Miner. 



f. Conformation and Its Relation to Milk Producing Ca- 



pacity in Jersey Cattle. By John W. Gowen. 



A brief review of some of the salient points of these papers 

 will be given under the appropriate division. The progress that 

 has been made in the solution of the other problems relating to 

 this work is summarized under the heading into which it may 

 fall. 



Analysis of Milk Records 



The records for milk production contained in the Advanced 

 Registries have been used in the investigations of the past year. 

 It will be remembered that the mean yearly milk yields at suc- 

 cessive ages have been determined for the Jersey and for the 

 Guernsey breeds. The 365 day milk records of the Holstein- 

 Friesian breed have furnished the material to determine the 

 •same information on this breed. A comparison of these results 

 is of a good deal of interest as it furnishes one of the best cri- 

 teria to determine whether the physiological effect of age on 

 milk production is the same on these three breeds and presum- 

 ably the same on all cattle. The necessity of establishing this 

 point needs little amplification for it is clear that only when the 

 point is established can the results determined for one breed 

 ■of cattle be generalized and the generalization applied to the 

 xest of the species. 



The curves describing the relation of age at calving to the 

 ■subsequent yearly milk yield are all logarithmic functions. The 

 equations themselves are. 

 Holstein-Friesian Milk Yield = 11351. 5+873. 67X — 32.225x 2 + 



1548.4 Log. x 

 where x equals the age in units of six months commencing at 

 one year and three months of age for the zero point. 



