Report on the Agricultural Experiment Stations, 1952 Page: 73
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RESEARCH IN LIVESTOCK PRODUCTION 73
The Georgia station did not find any correlation between growth
rates of pigs and bacterial count when they were fed penicillin or
streptomycin with corn-soybean meal ration in dry lot. Penicillin
seemed to increase total bacteria, whereas streptomycin had no effect
on bacterial count. Both drugs were effective in improving the
growth rate and the feed efficiency of the pigs.
If an antibiotic is fed to lactating sows some of it is transmitted to
the milk, but not in sufficient quantity to benefit suckling pigs, according
to the Iowa station. However, a practical method of supplying
antibiotics to baby pigs has been developed by the Arkansas station.
Bacitracin pellets implanted in the skin of suckling pigs at 2 to 5 days
of age increased their weaning weights as much as 11.3 percent over
their nontreated litter mates. In this experiment a 1,000-unit level of
the antibiotic was more effective than 2,000 or 4,000 units.
Contrary to results obtained at most stations, the North Dakota
station reports that tests made on weanling pigs with four different
antibiotics and drugs failed to produce any significant improvement
in growth rates. Pencillin, bacitracin, terramycin, and an arsonic
acid were used in these experiments. The results indicate that environmental
conditions may be an important factor. The addition
of aureomycin to an 8-percent protein ration for growing pigs proved
unprofitable at the Montana station; however, sows on rations supplemented
with this antibiotic during gestation and lactation farrowed
and weaned more pigs than the control lot.
A new growth stimulant
Tests conducted by the Michigan station with a surface-active agent
indicate that it may have an "antibiotic-like" effect in swine rations.
Gains of pigs fed a balanced ration in addition to the detergent were
equal to those of pigs receiving the same ration and an antibiotic.
Both lots gained at the rate of 1.3 pounds daily. As yet there is no
explanation for the growth-promoting properties of the compound.
The Illinois station has conducted a fundamental study to determine
the physiological causes of genetically different growth rates in
two lines of Hampshire swine. Pigs of the rapid-growth line consumed
more than twice as much feed daily and gained three times
faster than those of the slow-growth line. At 180 days of age the
average difference in weight of the two lines was about 62 pounds.
Anterior pituitaries of pigs from each line slaughtered at different
ages were assayed for growth-hormone potency by injecting some of
the pituitary powder into rats from which the pituitary glands had
been removed. The assays showed that the more rapid growth of one
line of pigs was accounted for by the fact that the pituitaries of these
pigs secreted more of the growth hormone. Another interesting discovery
was that 57-day-old pigs had as much growth hormone per
unit of pituitary tissues as they did when fully grown. The physiologists
concluded that growth in animals stops when they reach maturity
because the amount of growth hormone secreted in relation to
body weight is no longer adequate to maintain growth. Future research
on this problem may reveal practical means for controlling
growth of animals.
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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/m1/75/: accessed March 23, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.