Report on the Agricultural Experiment Stations, 1952 Page: 72
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72 REPORT ON EXPERIMENT STATIONS, 1952
source of amino acids it is important to know which amino acids are
needed by the pig, and the minimum requirements for each of these,
in order that the protein content of the ration may be properly
Recent experiments at the Indiana station have shown for the first
time that the amino acids arginine, leucine, phenylalanine, and valine
are required for optimum growth of weanling pigs. Earlier work at
the Indiana and New York (Cornell) stations had established the
essential nature of histidine, isolucine, lysine, methionine, threonine,
and tryptophan for growing pigs. In the latest experiments pigs fed a
purified diet containing all 10 of these amino acids, plus diammonium
citrate as the source of protein (nitrogen), made an average daily
gain of 1.2 pounds.
On an arginine-deficient diet similar pigs gained only 0.7 pound
daily, whereas pigs on a phenylalanine-deficient diet barely maintained
their initial weight. In the absence of either leucine or valine
an average daily loss in weight of 0.2 pound per pig was sustained.
Further experiments to determine the quantitive requirements for
these four animo acids are in progress.
Role of antibiotics
Discovery of the important growth-promoting effects of antibiotics
for swine and poultry has stimulated intensive research by the experiment
stations, the Department, and private industry to learn how the
various antibiotics actually function in animal metabolism, as well as
their limitations, practical possibilities, and long time effects.
Following a re-evaluation of the protein requirements of swine, the
Iowa station reports that previously recommended levels of protein for
producing market hogs in dry lot can be reduced 2 to 4 percent when
the hogs are fed a balanced ration and an antibiotic. Essential minerals
and B vitamins (including B12) are important also. Protein
levels of 14, 11, and 8 percent for pigs of three age classes-weaning
weight to 75 pounds, 75 to 150 pounds, and 150 to 200 pounds-produced
gains equal to any of three higher levels when supplemented
with 10 milligrams of aureomycin per pound of ration. Pigs receiving
the antibiotic gained about 10 percent faster and consumed 23 pounds
less feed per 100 pounds of gain than control pigs. Carcass yields,
depth of back fat, and percentage of lean were not significantly affected
by the antibiotic or protein content of the ration. The lower protein
levels could save hog producers in Iowa alone the estimated sum of
The Michigan station obtained equally good growth in pigs by
adding terramycin to rations containing 18 or 15 percent of protein.
Terramycin improved the rate of gain in pigs 21 to 37 percent, and
increased the efficiency of gain at all ages from weaning to slaughter.
The response was greatest, however, during the early growth period.
It is believed that antibiotics may promote growth by favoring
development of intestinal flora that synthesize growth factors or
inhibit undesirable organisms. The Illinois station reports that
chloromycetin fed with a synthetic milk diet temporarily reduced
the number of coliform bacteria found in the feces of baby pigs reared
in wire cages, but that after 10 days the bacterial count was normal.
Aureomycin had no effect on numbers of fecal bacteria. Both chloromycetin
and aureomycin gave good growth response.
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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/m1/74/: accessed April 24, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.