Jan. 20, 1919 Var iations and Mode of Secretion of Milk Solids 



81 



elude chiefly the determination of the relation of this milk and butter fat 

 as it varies within itself and as it varies with age. They do not con- 

 sider the relation of the variation of the other solids; in fact, the avail- 

 able material has been wanting. Such variation constants are highly 

 desirable; in reality, indispensable for the succeeding studies that are to 

 follow. 



These Holstein-Friesian data are exceptional in that they are accurate 

 data taken from one breed under the best of conditions. The material 

 as tabled is taken from volumes 18 to 28 of the Advanced Registry of the 

 Holstein-Friesian Association (75) for their semiofficial year records. All 

 of the records for milk, total solids, butter fat, and solids-not-fat are for 

 365 days. The constants are calculated from the grouped frequencies of 

 the formed correlation tables (IV to IX). It is evident from the correla- 

 tion table for age and percentage of solids-not-fat that one error probably 

 exists in the records either from a typographical cause or from an error 

 in the determination. I shall therefore give the constants both for this 

 animal included and for the distribution where it is omitted. Table I 

 shows the means, standard deviations, and coefficients of variation of the 

 variates. The two values of some of the constants in this table are, first, 

 those for the whole population of the Holstein-Friesian milch cows, and 

 second, those for the population which also records the values for the 

 total solids. 



Table I. — Fundamental constants /or Holstein-Friesian mean production of milk 



Character. 



Amount of milk pounds. . 



Do do... 



Age years. . 



Do do 



Butter fat pounds . . 



Do do 



Solids-not-fat do 



Do do 



Total solids do 



Do do... 



Butter fat per cent. . 



Solids-not-fat do 



Do do... 



Total solids do ... . 



Do do... 



Num- 

 ber of 

 individ- 

 uals. 



1,387 

 334 



1,387 

 334 

 335 



1,387 

 335 

 334 

 335 

 334 



1,387 

 335 

 334 

 335 

 334 



Mean. 



15,417-44 ± 67 

 15,149-70 ±111 

 4- OS ± 

 4-49 

 515-37 

 528.01 

 1,302.86 

 1,301. 20 

 1,814.78 

 1,812.92 ± 12 

 3-44I± 

 8.6i2± 

 8. 6o4± 

 12.02 ± 

 12. 0141b 



7667 

 3272 

 0369 

 0838 

 9956 

 4334 

 5828 

 5489 

 9929 

 9723 

 0058 

 0134 

 0124 

 0206 

 0202 



standard deviation. 



Coefficient of 

 variation. 



3,741-59 ±47 



3,016. iS ±78 



2. 04 ± 



2. 27 ± 



108.43 ± 2 



134-36 ± I 



260. OS ± 6 



258. 71 ± 6 



352-59 ± 9 



351.46 ± 9 



-3i8± 



.364± 



-338± 



.56o± 



-547± 



9111 

 7223 

 0261 

 0592 

 8256 

 7204 

 7769 

 7523 

 1884 

 1731 

 0040 

 0094 

 0088 

 0146 

 0143 



24. 268±o. 

 I9-909± - 

 50.37I± - 

 50. S56±i. 

 2I.039± . 



25. 446± . 

 19-959± - 

 19.S82± . 

 I9-429± - 

 19. 386 ± . 



9. 228± . 



4.22I± . 



3-923± - 



4-657± - 



4. 549± . 



3285 

 5398 

 7919 

 6218 

 5720 

 3334 

 5404 

 539° 

 5250 

 5246 

 I191 



IIOI 



1025 

 1215 

 1188 



The following facts are easily deducted from Table I : The Holstein- 

 Friesian cows making the semioflticial record have a mean milk production 

 of slightly over 15,000 pounds of milk, containing about 520 pounds of 

 butter fat and 1,300 pounds of solids-not-fat. The ratio of the solids- 

 not-fat to the butter fat is approximately 2.5 to i. Taken in the form of 

 percentages, the Holstein-Friesian milk contains slightly over 1 2 per cent 

 of total solids, composed of 3.43 per cent of fat and 8.60 per cent of solids- 

 not-fat. The mean age of the group is slightly more than 4 years. The 

 animals who have total-solids records are, on the average, about >^' year 



