Belt Valley times., 1926-07-22
DAIRY
FACTS
SIRE'S DAUGHTERS
INDEX OF VALUE

fPrepared By the United States Department
OF AKricuirure.)
A great dairy sire Is one whose
daughters have a high yield OF milk
and butterfat, a high average Increase
In milk and butterfat yield over their
dams, and a high percentage OF their
number better than their dams. says
r. r. Graves OF the bureau of dairy
Ing, United States Department Of Ag-
riculture All these things must be
taken into consideration when meas
uring the value of dairy sire, he
says. No one Of them alone offers suf-
hcIent evidence OF the sire's worth.
In a study OF q Hoistein-FriesIan
sires, each having six or more tested
! daughters from tested dams, some con-
elusiens were arrived at concerning
the hereditary transmission of produc-
uon, says Mr.. Graves. Some of the
slres In the list raised both the milk
yield and the percentage OF butterfat
of their daughters as compared to
the production of their dams. Some
raised one and lowered the other.
Some lowered both. But no one sire
raised both the milk and butterfat per-
centage Of all his daughters. nor did
any one sire lower these records Of
all his daughters. In other words
while the sires evidenced a prepO-
tency for raising or lowering produc-
ton, no one sire was completely pre-
potent
The ability of a sire to raise or
ower the yield Of his daughters does
not necessarily have a correlation with
the record of his own dam. Rather,
the prepotency of a sire seems to de-
pend upon the combination OF factors
governing the Yield of milk and per
rentage Of butterfat that he has in
herited from his parents. If he has
inherited only factors that will deter
mine high milk yield and high per-
rentage OF butterfat, he will be pre-
potent In impressing these characters
On his offspring If he and the dams
with which he is mated have Inherit
ed from their parents mixture of
the factors for both low and high pro
iuction, which is often the case, q
variety of combinations In the differ
ent offspring Will follow, and they
will be of varying degrees Of prOduc-
ing ability.
The evidence seems to point to both
parents contributing equally to the
inheritance governing the milk and
outterfat producing capacity of their
daughters, says Mr.. Graves. But. II
one parent Is homozygous or pure
for the hereditary factors determin-
ing high production and the other par
ent is heterozygous, or mixed, In its
inheritance, then the homozygOus par
ent will have the greater influence on
the producing capacity of the daugh-
ter: vet their daughter will transmit
to a part of her progeny the Inherit
ance for low production that she may
receive from her heterozygous parent.
For two heterOzygous parents, 1t is to
be expected that the daughters will
show a great range in producing ca
pacity from very poor to very good.
The fact that the percentage of but
terfat and the milk yield are inherited
independently, at least within limits,
and that both the sire and the dam
contribute to the inheritance of their
daughters, governing both milk yield
and percentage of butterfat, indicates
that Improvement in yield Of butterfat
can be brought about by selection for
both milk yield and percentage Of but
terfat.
The big problem is to locate the
sire that has inherited only the fac
tors determining a high producing ca
pacity. The degree to which he has
Inherited these factors can be de-
termined only by testing large num-
ber of his daughters and comparing
their records with those Of their dams.
The increasing number of records
Of daughters and their dams becom-
ing available through the cow-testing
furnishes a means of cal
.ulnting the comparative worth OF a
greater number of sires than has been
possible in the past. The % sires
In this study were given comparative
ranking in a new method devised by
Mr.. Graves Each sire was ranked
IN comparison with the others with
respect to milk yield of his daughters,
average butterfat yield, average in
crease of milk yield. average increase
IF butterfat, and the percentage Of
daughters that were better than their
iams In milk and butterfat yield. His
value was indicated by
he sum Of his ranking In the various
.lasses.
The complete discussion OF this
study has been published In Depart
nent Bulletin No. 1872, Just issued. A
,opv may be obtained, while the sup
,ly lasts, by writing to the United
states Department OF Agriculture,
d. c.
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