AS-393 March 1970
The Value of Chlortetracycline and Sulfamethazine
for the Conditioning of Newly Arrived Cattle in the Feedlot
W. M. Beeson3 T. W. Ferry and M. T. Mohler Department of Animal Sciences
Summary
In five experiments the feeding of a combination of 350 mg. of aureomycin (chlortetracycline) plus 350 mg. of sulfamethazine (AS-700) daily to newly arrived steers resulted in an average of 29% increase in daily gain and a 27% improvement in feed efficiency (Tables 1, 2 and 4). Steer calves administered AS-700 per os weighed on an average 16 pounds heavier at the end of 28 days than the controls. No steers required treatment for shipping fever among the groups fed AS-700, while the incidence of sickness among the control steers requiring medication varied from 0 to 30 per cent. The 16 pounds extra weight occurring on the AS-700 steers was pure profit because the saving in feed paid for the cost of feeding AS-700 for 28 days.
The estimated cost of using AS-700 for 28 days is about 50<£ to $1.00 per head. Every dollar invested in AS-700 returned about $4.00 in terms of extra beef.
Also, it is interesting to note that feeding 350 milligrams of aureomycin alone resulted in a significant (P < .05) increase in daily gain and provided some real protection from shipping fever (Table 1). In contrast, feeding sulfamethazine alone caused no significant change in gain or feed efficiency (Table 1). Apparently there is some complementary synergism between aureomycin and sulfamethazine. In all experiments there was a dramatic improvement in efficiency of feed conversion with AS-700, even though this combination was not always superior to
aureomycin from the standpoint of gain. AS-700 provided more protection from shipping fever complex than aureomycin.
Feeding 10 mg. of stilbestrol to steers either singly or in combination with AS-700 caused no significant improvement in daily gain or feed efficiency (Table 2).
The proper use of AS-700 should help solve one of the major problems in the cattle feedlot industry, namely improving the growth, feed conversion and health of shipped-in cattle. —

This series of research studies have given very consistent, clearcut data which has been confirmed by research at university experiment stations in Arizona, Iowa, Kansas, Texas and South Dakota (Table 4).

Introduction
Shipping fever of cattle is an acute infectious disease characterized by fever, dyspnea and fibrinous pneumonia. It is a disease very similar to the common "flu" in humans and is brought on in cattle by the stress of shipping starvation and new environment.
This disease, and other diseases associated with shipped-in cattle, is one of the greatest losses to the beef cattle industry and is estimated to cost about 25 million dollars per year.
Many factors are involved in preventing the shipping fever syndrome, namely (1) good
Beef Section • Animal Sciences Department Cooperative Extension Service, PURDUE UNIVERSITY, Lafayette, Indiana
Nutrition  Beef