Report on the Agricultural Experiment Stations, 1953 Page: 22
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22 REPORT ON EXPERIMENT STATIONS, 1953
attempting to overcome this difficulty by growing virus in pig tissues.
Since lung and liver tissues from pigs had not previously been grown
outside the body, the first step was to find the proper nutrient conditions
for them. Bits of lung tissue from 5- to 10-day-old pigs have
now been grown in flasks, in a carefully buffered solution containing
embryo extract and serum ultrafiltrate. Virus of known concentration
is now being serially passed through such cultures at 5- to 7-day
intervals. This material will then be inoculated into baby pigs to
test survival or multiplication of the virus. If growth occurs an
attempt will be made to produce a tissue culture vaccine. Recent
studies at the Indiana station show that freezing and storage at low
temperatures enabled the virus to remain active for 3 years. Attempts
by this station to alter the course of TGE in pigs with several antibiotics
and drugs were ineffective.
The Michigan station is seeking to establish the quantitative requirements
of the young pigs for various vitamins and to obtain
information on the pathology of vitamin deficiencies. Baby pigs fed
a synthetic milk diet, deficient in riboflavin, gained only 0.01 pound
daily, and developed a rough hair coat, scaly dermatitis, and diarrhea.
A deficiency of pantothenic acid resulted in persistent diarrhea within
2 to 3 weeks and muscular incoordination within 3 to 5 weeks. The
experiments indicate that the baby pig requires between 1 and 2- milligrams
of pantothenic acid, and between 0.2 and 0.3 milligrams of
riboflavin per 100 grams of dry matter in the diet.
Through controlled experiments, the Iowa station has established
that weanling pigs require a minimum of 0.4 milligram of vitamin
B12 per 100 pounds of feed for optimum growth. When fed a ration
deficient in B12 the pigs became emaciated and unthrifty, but they
recovered promptly when B12 was injected intraperitoneally, or fed
in the ration.
Modern methods used in the extraction of fat and oils from comnercial
feeds commonly used for swine have resulted in rations of
lower fat content than formerly used. This has stimulated research
to learn more about the dietary fat requirements of swine. Pigs fed
a fat-free ration by the Indiana station developed a scaly dermatitis,
dull hair coat, necrotic areas, and unthrifty appearance within 40
to 60 days. Growth rate and feed efficiency were markedly reduced,
and sexual maturity was delayed in comparison with littermates that
received a ration containing 5-percent fat.
The problem of reducing baby pig losses and improving litter size
and performance is also being studied through research designed to
improve nutrition of the sow during gestation and lactation. Gilts
fed aureomycin at the rate of 20 grams in a ton of their gestation
ration, by the Indiana station, farrowed more and heavier pigs than
those receiving only the well-balanced basal ration. The death rate
of pigs during the first three critical days was about 7 percent more,
however, than in the control lot. Continuing the aureomycin in the
rations of gilts and their litters through the lactation period resulted
in slightly heavier and stronger pigs at weaning. At the Michigan
station supplementation of a well-balanced gestation ration with only
9 milligrams of aureomycin per pound of feed resulted in a small
increase in litter size and birth weights and in number of live pigs.
The West Virginia station has been evaluating certain fish and
animal byproducts as sources of unrecognized nutritional factors, that
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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/m1/24/: accessed April 28, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.