Report on the Agricultural Experiment Stations, 1952 Page: 74
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74 REPORT ON EXPERIMENT STATIONS, 1952
Of the 30 percent of pigs born each year that never reach market,
more than 1 million die soon after birth from chilling. A study of
the effects of chilling on body temperature and blood changes of pigs
up to 3 weeks of age by the Michigan station shows that the body
temperature regulating mechanism of the new-born pig is only partially
developed. A temperature drop of 3 to 13 F. in baby pigs
was observed during the first 30 minutes after birth, after which there
was a gradual return to normal. The period of adjustment was about
2 days at a temperature of 60 to 75, although 10 days' adjustment
was required at freezing temperature. Pig weight at birth was highly
correlated with the ability of the pig to adapt itself to its environment.
Small pigs that did not have access to the sow's milk quickly
chilled. Chilling of pigs 1 to 2 days old generally resulted in a decrease
in blood cell concentration and an increase in blood sugar content.
By providing warm quarters for sows at farrowing time, farmers
can greatly reduce baby pig losses.
Breeding better hogs
By developing superior inbred lines and systematic methods of
using them in crosses, swine breeding research is providing the means
for achieving greater efficiency and obtaining better quality in pork
Results obtained from linecrossing and cross-breeding trials by the
Minnesota station (coop. USDA) show that the increase in litter size
survival rate, weaning rate, and rate and economy of postweaning gain
was greatest in cross of strains that were least related. The favorable
influence of hybrid vigor on pig performance of the cross-bred progeny
was more pronounced during the suckling period than after weaning.
The advantage of average single crosses over parent lines, for
the five factors studied, ranged from 5.4 percent for a narrow cross
to 13.5 percent for a wide cross. Crisscrosses and rotation crosses
were 13.03 and 13.83 percent superior, respectively, to parent stocks.
Rotation crosses of lines that differed most genetically were 4.5 percent
superior to narrowly divergent rotation crosses.
Litters from Duroc gilts mated to inbred boars of different breeds by
the Ohio station were heavier at 150 days of age, required less feed per
100 pounds of gain, and yielded leaner carcasses than outbred or rotation
line cross Durocs. In the 1951 trials, litters by inbred Poland,
Yorkshire, and Landrace-Poland boars from Duroc gilts averaged 9.1,
9.4, and 9.8 pigs at weaning and 1,699, 1,611, and 1,747 pounds in
weight at 150 days. Outbred and rotation line cross Durocs weaned
8.4 and 8.5 pigs per litter that weighed 1,409 and 1,502 pounds at 150
In a 4-year study conducted by the Wisconsin station (coop. USDA
and farmers), topcross gilts sired by inbred boars produced and
weaned more pigs and heavier litters than conventional matings. The
difference in favor of gilts by inbred boars amounted to slightly more
than 1 pig per litter at farrowing and weaning, and about 37 pounds
in weight of litters weaned.
Although sheep and wool production in the United States declined
severely between 1942 and 1950, research by the State experiment stan
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United States. Office of Experiment Stations. Report on the Agricultural Experiment Stations, 1952, book, January 1953; Washington D.C.. (digital.library.unt.edu/ark:/67531/metadc5990/m1/76/: accessed March 29, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.