Medicines Make Meat
By A COUNTRY DOCTOR
THE world's biggest economic problem is how to meet ever- increasing demands for food and raw materials. Despite fertilisers, tractors, combine harvesters and the control of many plant diseases, the amount of food which is grown is still a long way short of human needs. In Britain, fortunately, there is no starvation, though the meat ration is now down to a dangerously small quantity ; but in other parts of the world many millions of men, women and children are quite unable to obtain enough food to keep in good health. In particular they lack the energy which only first-class proteins—milk, meat, eggs and fish—can provide. Short cuts to increased food-production arc badly needed, and, strangely enough, it is medical science which has recently opened up a most promising field of research.
The first discovery which the farmers took over from the doctors was that the drug thiouracil improved "feeding efficiency " ; in other words, it helped to ensure that cattle, pigs and poultry converted their expensive feeding-stuffs into profitable meat, milk and eggs. Thiouracil is prescribed by doctors to depress over-active thyroid glands. This gland manufactures a substance known as thyroxin, and in Graves' disease (or hyperthyroidism) it works overtime. The effect of thiouracil is to neutralise the excess thyroxin ; the meta- bolism slows down, lost weight is regained and the patient's air of anxious excitement disappears.
The idea that a drug could reduce the speed of chemical processes in the body appealed to farmers, who like to sell their beasts at top weight but dislike the expense of fattening them. If human patients could put on weight with the help of thiouracil without increasing the amount of food eaten, could animals be fattened by the same inexpensive process ? Experiments soon provided the answer. Animals given thiouracil used less food for energy and more went into store as fat or muscle. In fact, these animals showed signs of what is recognised as hypothyroidism in human beings—slowness of mind and body combined with thickness of skin. One of the first practical tests with thiouracil in husbandry showed that cockerels given the drug in their food were able to attain the same weight as control animals (i.e., animals not given the drug) which were consuming 25 per cent. more food. In turkeys the amount of feeding-stuffs required to ensure a regular weight-gain could be reduced by 16 per cent. when thiouracil was added to the diet, and, to the delight of agriculturists, cattle, sheep and pigs have reacted in the same way.
These experiments with thiouracil have recently been put into the shade by a much more important development. In 1948 a chemical substance was isolated which had long been sought (ever since the discovery that treatment with liver had a specific effect) as the factor essential for the control of pernicious anaemia. It was called vitamin 1312, and it is now being widely and successfully used for the• treatment Of That disease and its complications. Research workers investigating the properties of vitamin B„ soon found that it was a powerful stimulator of growth in animals. When the vitamin was added in minute quantities to the feeds the animals grew much more quickly than they would ordinarily have done. Furthermore, the addition of the vitamin to a vegetable diet had the effect of raising it to the standard of one containing proteins from animal sources.
Vitamin B„, however, appeared to be only one constituent of what biologists have been calling the "animal protein factor," and it was during further research that the quite unexpected discovery was made that another important new drug stimulated growth in animals even more strongly than vitamin B„. This drug is aureo- mycin, which probably has a wider range of action against bacterial infections than any other known drug. It is one of the latest of the antibiotic group, of which penicillin was the first and streptomycin the second. Up to now aureomycin, like the other antibiotic drugs, has been regarded solely as a weapon for fighting infections ; though supplies are limited in this country it is being successfully used in many parts of the world for serious diseases such as pneumonia and septicaemia. Aureomycin's only point of resemblance to vitamin B12 is in its method of manufacture—both are obtained from a mould by a fermentation process—and it is not yet possible to explain why it should possess this extraordinary property of stimulating growth in animals.
One of the greatest disappointments in the history of therapeutics was the discovery that disease,causing bacteria which at first seemed highly susceptible to the sulphonamides and penicillin could develop " resistance " to these drugs. The same disadavantage attends the use of streptomycin. This is particularly unfortunate, because if it were not for their capacity to develop resistance the germs of tuberculosis would have suffered a heavy defeat at the hands of this drug. Now bacteriologists have just had an even greater shock than that caused by the discovery of bacterial resistance. It seems that some bacteria can do more than resist the antibiotic drugs ; they can even thrive on them, provided the dose is not too large. In some remarkable experiments two American workers were able to show that mice infected with a strain of bacteria which had learned in the laboratory to thrive on streptomycin recovered if untreated but died if streptomycin was administered. The drug, instead of killing the bacteria, apparently stimulated their growth to such an extent that the animal's natural powers of defence were overcome.
It may be also that the sulphonamide drugs can stimulate the growth of bacteria. U.S. naval doctors considered the possibility as long ago as 1945, when men who had been given courses of treat- ment to prevent infection by streptococci developed sore throats and scarlet fever in greater numbers than the untreated men. There is no doubt that penicillin too, when provided in the right concen- tration, can stimulate certain bacteria, and it has recently been suggested that it may perhaps act as a special spur to -the growth of tuberculosis germs.
–__So far there has been no report that bacteria can thrive on aureo- mycin, but in view of what has been learned about the other antibiotic drugs it would not be altogether surprising if some such development does take place. On the principle of having too much of a good thing it is conceivable that what may be a powerful stimulant of growth in small quantities could be destructive to bacterial life in heavy concentrations. Whatever the biological explanation of aureomycin's growth-promoting properties, farmers in the U.S.A. will soon be benefiting by them, for it is reported that the addition of five pounds of an unpurified product—selling at 30-40 cents a pound and requiring neither fertile soil nor expensive raw materials for its production—to' a ton of animal feed has increased the rate of growth of hogs by as much as 50 per cent. Chickens and turkeys have grown at an equally startling speed. In a world of dwindling resources and expanding populations this is certainly a tonic discovery.
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