Sept. 15, 1919 



Variation in Milk of Ayrshire Cows 



299 



Table IV. — Constants for variation in percentage of fat in the milk of Ayrshire cows. 



Age of cow. 



Mean fat per- 

 centage. 



Standard de- 

 viation (in 

 percentage). 



Coeflficient of 

 variation. 



3 years. 



6 years. 



8 years . 



16 years. 



Weighted means (total). 



1908 



1909 



Combined. 



jgo3. 



1909 



Combined. 



190S 



1909 



Combined. 



1908 



1909 



Combined. 



1908 



1909 



Combined . 



1909 



Combined . 



1908 



1909 



Combined. 



1908 



1909 



Combined. 



1909 



Combined. 



1908 



1909 



Combined. 



1908 



1909 



Combined. 



1908 



1909 



Combined. 



1908 



1909 



Combined. 



1909 



Combined. 



1908 



1909 



Combined. 



891 ±0. 

 82s ± 

 852 ± 



924± 

 9IS± 

 89s i: 

 903± 



770± 

 78s ± 

 780 i: 

 77S± 



741 ± 

 694 ± 

 7x6i: 



705 ± 

 672± 

 68s ± 



694 ± 

 b6g± 

 69I± 



658 ± 

 668± 

 664± 



6i8± 

 652± 

 636± 



599± 

 601 ± 

 6oo± 



6S3± 

 608 ± 

 629± 



6io± 



591 ± 

 599 ± 



7oo± 

 559± 

 6o6± 



595 ± 

 589i: 



592 ± 



500± 

 Soo± 

 500 i: 



8oo± 

 6i7± 

 662 ± 



O. 292±0. 024 



.3I3± .021 



.3lii: .016 



1 .4I2± .008 



6 .384^ .007 



.344± .006 



.36l± .005 



.359± .008 



c.342± .007 



<i .326± .006 



.342± .005 



.3S8± .008 



•335± -oo? 



.346± .006 



.3I4± -008 



.322± .007 



.3I9± .005 



.3I2± .008 



.305± .008 



• 3o8db .006 



.3o6± .009 



.323± .008 



• 3l6± .006 



.3I3± -oio 



.294± .009 



•303± -007 



.3o8± .013 



• 278± .009 

 .29I± .008 



.312± .015 



• 3o6± .014 



• 3io± .oio 



.286± .019 



.338± .020 



.326i .014 



.288± .030 



.273± .020 



.285± .017 



.27I± .028 



■iSi± -040 



.3I0± .023 



.096± .032 



.225± .023 



.2i6± .022 



.igSi .067 



.I3i± .026 



.'!■^o±. .029 



7.496±0. 611 



". i8o± .552 

 .o8oi: .415 



da. 



3-738 



SOO± . 202 

 8i6± .191 

 820± . 148 

 26oi: . 118 



5i3± .200 

 034± . 179 

 626± . 171 

 055± .131 



579± -223 

 074± . 198 

 320± . 149 



481 ± .225 

 772i: ■ 193 

 664± . 147 



448± .228 

 259± . 200 

 334± • ISO 



358± .244 

 801 ± .221 

 6i7± . 164 



64o± . 28s 

 047 ± .245 

 336± .187 



569± .367 

 73 2 ± .266 

 072± .217 



5S2± .424 

 48oifc .392 

 S36± .289 



936± .538 

 4I2± .557 

 o66± .405 



785± .815 

 684± .576 

 942± .487 



7. S27± .770 

 9. 83s ±1.116 

 &64ii: .656 



2. 736± .923 

 6. 436± .707 

 6. i8o± .646 



$. 2o8±i. 761 

 3.62S± . 707 

 4-65o± .786 



8.827 



"I Including the two very high testing cows. 

 * Without the two very high testing cows. 



<^ Including the one very high testing cow. 

 <* Without the one very high testing cow. 



From these tables a number of points are to be noted, 

 I. It is evident that the mean weekly yield and the fat percentage 

 change with the age of the cow. The nature of these changes will not, 

 however, be discussed here but will be analyzed in detail in a later sec- 

 tion of the paper. 



