Gowen: Transmission of Milk Yield 301 
for three years four months is corrected 
to the expected record at two years, 
and the four years six months record to 
the expected record at two years. 
These three records are then summed 
and the average taken. This average 
is the record used as the milk produc- 
tion of the crossbred. These average 
records have been used as the measure 
of the cow’s milk production because 
the work of Gaven’ on British Hol- 
steins and of this laboratory on the 
Jersey’ has shown that the mean of two 
or more lactations is a better measure 
of a cow’s capacity as a milk producer 
than is the record of one lactation. 
These records have been brought up 
to the date of May 1, 1920. 
The milk yields for the dams of the 
crossbreds are obtained in a similar 
manner to those for their crossbred 
daughters. 
THE SIRES’ POTENTIAL MILK PRODUC- 
TION 
The records for the sires Taurus 
Creamelle Hengerveld and Lakeland’s 
Poet are obtained as follows. The 
records of all daughters of these sires 
from dams of their own breeding are ob- 
tained in a similar manner to that de- 
scribed for the crossbred females. These 
records showing the milk production of 
each daughter of a given sire, other 
than crossbred, are then summed and 
the mean taken. This mean is used 
as the sire’s potential transmitting 
ability. The measure used is conse- 
quently the progeny performance test 
for the hereditary composition of the 
sire for milk production. 
The composition for milk production 
transmission of the Holstein-Friesian 
bull, Delva’s University De Kol, where 
no pure offspring are available is that 
of Taurus Creamelle Hengerveld. It 
is realized that the use of this milk 
production to describe the transmit- 
ting ability of Delva’s University De 
Kol is open to serious criticism. No 
purebred offspring are available from 
which an accurate test of this bull’s 
composition could be made. In view 
of this contingency two fairly strong 
arguments support the choice of Tau- 
rus Creamelle Hengerveld’s transmit- 
ting ability to represent that of Delva’s 
University De Kol. The bulls are of 
the same breed. The dam of Delva’s 
University De Kol, Delva Johanna De 
Kol had a milk yield closely resembling 
that of Taurus Creamelle Hengerveld’s 
potential yield, as may be seen by a 
comparison of the sire’s curve in the 
second graph of Figure 14, with the 
dam’s curves of the third graph for the 
same figure. 
Likewise the daughters of the sire 
of Delva’s University De Kol, Johanna 
Lad Manor De Kol 41913 were simi- 
lar in milk production to those of Tau- 
rus Creamelle Hengerveld. These facts 
consequently make it seem altogether 
probable that the milk transmitting 
capacity of Delva’s University De Kol 
is correctly represented. 
The transmitting qualities of Kayan, 
the Aberdeen Angus bull, were taken as 
the mean corrected two years old records 
of the purebred herd of Aberdeen An- 
gus cows. The use of this record for 
Kayan can only be defended on purely 
a priori grounds. Until such time as 
his daughters come in milk this pro- 
cedure will be subject to criticism. 
Kayan’s pedigree does lead to the be- 
lief that his milk transmitting record 
has been correctly represented in the 
diagrams illustrating these data. 
Figure 14, first graph, shows the milk 
record of Crossbred No. 1 on a monthly 
basis corrected to the age of two years. 
This record is shown by the solid line 
(———————_). The mating to pro- 
duce this crossbred was a Jersey bull, 
Lakeland’s Poet 102603, bred to a 
Holstein-Friesian cow, Pauline Posch 
81048. The milk production of the 
dam Pauline Posch, on a monthly 
basis corrected to the two year age ex- 
pectation, is given by the dotted line 
(GES eee ). The expected poten- 
3 Gavin, William. 1913. Studies in Milk Records. On the Accuracy of Estimating a cow's 
milking capability by her First Lactation Yield. 
Studies in Milk Secretion. V. 
In Genetics, vol. V, no. II, pp. 111-188. 
4Gowen, John W. 1920. 
of Milk Secretion with Age. 
In Jour. Agr. Sci., vol. 5, pt. 4, pp. 377-390. 
On the Variation and Correlations 
