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Show By Robert S. Murdock County Agricultural Agent THE ROLE OF ANTIBIOTICS IN ANIMAL NUTRITION While much is still unknown regarding the precise way in which antibiotics work in producing pro-ducing growth stimulatory effects, ef-fects, intensive experimentation has indicated some general principles prin-ciples regarding their most successful suc-cessful application. Antibiotics are most effective as growth stimulants in feeds for non-ruminants, such as hogs and poultry, and the maximum effects occur early, in life, during dur-ing the period of most rapid growth. Likely the effects of antibiotics an-tibiotics are brought about largely through their action on undesirable bacteria in the intestine, in-testine, at least many of the most marked growth-promoting effects have been noted when animals have been kept under unsanitary conditions or where they are suffering from subacute sub-acute intestinal diseases. This should not be interpreted as meaning that antibiotic administration adminis-tration will take the place of proper sanitation and management manage-ment practices. The effectiveness effective-ness of antibiotics in rations is lowered at advanced stages of growth, and it may be desirable to withdraw them from rations of poultry after about eight weeks or swine after about 16 weeks of age. Such withdrawal should probably not be made at a time when enviromental chan. ges, such as altered feeding or housing occur. Use of antibiotics in creep feeds for swine, in order or-der to get them to the animals as early as possible, would seem to be a useful practice. GRAIN - FATTENING . PASTURE I have been asked a number of times as to' whether or not it. pays to 'grain feed steers that you are fattening on pasture. To answer that, two important points have to be taken into consideration: 1. High grain cost. 2. The market demand for medium grades of beef. Cornell University conducted trials over a period of three years along this line. Several points in the summary of these trials are of interest. 1 1. The date emphasized the importance of excellent pastures for fattening on grass alone. 2. On pastures capable of producing pro-ducing 1.5 pounds daily gain, it paid to feed about 1200 pounds of corn per steer. This increased the value of steer $3.89 per cwt. 3. Pasture alone (the 1.5 lb. daily gain kind) produced medium med-ium steers dressing 53 per cent. Our best pastures, we feel, will yield two pounds daily gain without grain. Eighty per cent of our beef demand, according to packers, is for the commercial commer-cial and good grade. Grass steers will make these grades |
