262 



Maine Agricultural Experiment Station. 1919. 



five lactations. If she was a medium producer she was only a 

 medium producer in these lactations. If she was a poor pro- 

 ducer in the first lactation she was also a poor producer in all 

 five lactations. Relatively the cows stayed very close to the 

 plane of production established by their first lactation for the 

 total of the other lactations. The correlations measuring these 

 relations are given in table 2. 



TABLE 2. 



Correlation Coefficient for the Milk Yield (8 Months of Lacta- 

 tion) of,- a Lactation of a Given Age and the Milk Yield 

 for the First Five Lactations of the Cow's Life. 



Age when Lactation Mean Milk Yield for Standard Deviation 

 Commenced that Lactation of Milk Yield 



2 years to 3 years 



3 years to 4 years 



4 years to 5 years 



5 years to 6 years 



6 years to 7 years 

 Total of first five 



lactations 



4159.1+ 57.8 

 4840.9+ 86.1 

 5380.7+ 78.8 

 5568.2± 87.1 

 5681.8+ 91.4 

 25613.6+335.9 



803.2+ 40.8 

 1197.9+ 60.9 

 1096.2+ 55.7 

 1211.2+ 61.6 

 1270.7+ 64.6 

 4672.0+237.5 



Correlation Coeffi- 

 cient for Lactation 

 Records and the first 

 five Lactation's To- 

 tal Yield 



+0.742+.032 

 .842+.021 

 .861+.019 

 .825+.023 

 .8.21+.023 



From this table a simple arithmetrical equation can be 

 found to predict the lactation of the five lactations from the 

 lactation of any age. These equations are : 



Five year total lactation yield=:7671.9+4.31x two year lactation yield. 

 Five year total lactation yield=9719.5-{-3.28x three year lactation yield. 

 Five year total lactation yield=5861.4-)-3.67x four year lactation yield. 

 Five year total lactation yield=7893.5-f-3.18x five year lactation yield. 

 Five year total lactation yield=8471.9+3.02x six year lactation yield. 



These results may best be put in tabular form for ease in 

 reference. In the table that follows the two year old lactation 

 record is chosen because it represents the most frequent record 

 in normal dairy practice. 



