Report on the Agricultural Experiment Stations, 1953 Page: 40
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40 REPORT ON EXPERIMENT STATIONS, 1953
Progress in breeding research
Swine breeding research results continue to emphasize the importance
of hybrid vigor in swine. This is obtained by crossing breeds,
and inbred lines within breeds or between breeds. Hybrid sows and
gilts generally have shown improvement in reproductive performance,
in growth rate, and in liveability and carcass quality of their pigs
compared with outbred sows. The large surplus stocks of lard and
other animal fats already available and the preference of consumers
for leaner pork, are among the factors responsible for increased
emphasis on the improvement of carcass quality as well as the reproductive
performance and overall efficiency.
At the Illinois station (coop. USDA) linecross sows mated to inbred
boars farrowed and weaned significantly larger litters than were
obtained in conventional outbred matings. The linecross pigs averaged
almost 6 pounds heavier at weaning than those farrowed by outbred
sows, and averaged 322 pounds more in their 154-day litter weight
than those produced by outbred sows. Carcasses of linecross barrows
were generally leaner and longer, and had less backfat than outbred
barrows of similar weight.
Litters of crossbred pigs produced by mating inbred boars to outbred
sows of cooperating farmers by the Pennsylvania, station (coop,
USDA) were heavier at weaning, gained faster, and reached a market
weight of 225 pounds in 158- days, compared with 176 days for
purebred pigs. The crossbred litters were slightly larger at weaning
but showed no advantage in number farrowed, percentage farrowed
alive, or birth weight over outbred litters.
Contrary to the opinion that either crisscrossing or continuous rotational
crossing of lines or breeds increases variability in performance
and tends to "run out," the Minnesota station (coop. USDA) reports
that these methods were effective in maintaining and improving on
the advantages of hybrid vigor obtained in first crosses.
A rotational crossbreeding system, in which inbred boars of four
breeds were used by the South Dakota station (coop. USDA), has
resulted in animals of early sexual maturity, high conception rate,
superior litter size, and superior gaining ability, compared with outbreds
or linecrosses within a breed.
Detailed carcass studies by the Oklahoma station (coop. USDA)
have shown that there are large hereditary differences in carcass
merit. The results also clearly show that rate and efficiency of gain
need not be sacrificed in breeding for improved meat quality and
carcass value. In line-cross progeny no important relationship was
found between rate of gain and carcass value, or between efficiency
of gain and carcass value. For example, three litters that made 100
pounds gain on only 304 pounds of feed had carcass values equal to
four other litters that consumed 373 pounds of feed for 100 pounds
A study of records on about 3,850 gilt litters made by the Wisconsin
station shows that crossbred litters have lower death losses than litters
from gilts bred to boars of the same breed. Although litter size at
birth and individual weaning weights were about the same for the two
systems of breeding, litters from crossbred gilts averaged almost 100
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United States. Office of Experiment Stations. Report on the Agricultural Experiment Stations, 1953, book, 1953; Washington D.C.. (digital.library.unt.edu/ark:/67531/metadc5989/m1/42/: accessed January 23, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.