Studies Being Made On Lean-to-Fat
Ration in Hog Breeding
How fast and how much can you
change the lean-tofat ratio in hog
carcasses through selective breed
ing'’ This is being answered
through basic studies at USDA’s
Agnultural Research Center,
Eeltsville, Md.
In three generations of selec
tion m Duroc hogs, choice for low
fat decreased backfat thickness bj.
31 per cent, while selection for
high fat increased backfat thick
ness by 14 per cent Animals
chosen with significantly less
backfat than heid average trans
nutted about 41 per cent of that
advantage to their offspring. On
the other hand, animals chosen
with more backfat than herd aver
age transmitted about 57 per cent
cx that disadvantage. Thus, selec
tion, was somewhat more effective
ia increasing backfat than in de
ci easing it.
Carcass samples of third-genera
tion Duroc hogs bred for leanness
gave 3 per cent more in yield of
trimmed hams, loins, and should
tr butts than the hogs bred for
fatness. At the same time, the
specially bred fat-line Durocs av
eraged 0 6 per cent higher m ba
con yield and 5 per cent higher in
percentage of other fat cuts
This means that for every 200-
pound Duroc marketed, third-gen
eration lean-line pigs averaged 6 2
pounds more lean cuts and 10
pounds less fat cuts than fat-lme
animals The latter yielded 12
pounds more bacon.
These differences are large, of
course. But progress in separating
the lean-to-fat ratio in succeeding
generations of the two lines may
not be as rapid.
Selection in the Yorkshire
breed is giving similar results
But more data are needed on the
Yorkshires to tell lust how effec
tive selection will be m this breed.
Tests of lean tissue for fat dis-
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t'nbution and flavor showed that
fat Durocs with 15 per cent
more intramuscular fat-produced
roast pork with more tenderness,
flavor, and juiciness than did lean
Durocs. Carcass and flavor data
lor these tests are being provided
b> ARS food technologist R. L.
Hiner and his associates.
ARS -geneticist H 0 Hetzer is
developing by selection a line
high in fatness and one low in fat
ness in each of two breeds Prr
niary criterion of selection is
backfat thickness at a live weight
of 175 pounds Only secondary
consideration is being given to
such traits as litter size, growth
late, and conformation.
The average difference in back
fat thickness between the lean
line and fathne Durocs was 0 4
inch in the first generation, 19
m the second, and 37 in the third
Aveiage backfat thickness m the
foundation stock was 1 49 inches
This increased to 1 70 inches m
tmrd-generation fat line Durocs,
and decreased to about 133
inches in thrd generation lean
line Durocs
Researchers believe that the dif
ference in lean-to-fat ratio will
become more pronounced as selec
tion continues Results also show
that selection for low backfat has
tended to increase length and
height and decrease body width,
Vvdnle selection for high backfat
has generally resulted in shorter,
lower, and wider bodied hogs.
State agricultural experiment
stations and private breeders, as
well as USDA, have been working
for years to imprhve purebred
hogs and develop superior cross
breds for efficient pork produc
tion. Selection for carcass qual
ity in swine based on backfat
thickness was started at Belts
ville in 1954, an outgrowth of in
creasing interest in the meat-type
■State
-State
hog.
The Beltsville studies, part of
this overall plan, are providing
useful data on the value of selec
tive breeding m producing meat
type hogs.
These studies will be continued
as long as selection is effective in
changing the lean-to-fat ratio.
Lancaster Farming, Friday, September 5, 1958—1
Non-fat dry milk is milk that
has had all the fat taken out of
it, leaving all the calcium, phos
phorus, protein and B-vitamins
vA /
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Because it contains all these n
tuents, adding non fat dry mi;
to regular dishes is a good way ■
make sure that every member <
the family gets enough milk.