Jay A. Daniel, Julie A. Baker, David G. Pugh, Misty A. Shores, Brian K. Whitlock, and James L. Sartin

Respiratory and digestive diseases take a heavy toll on the cattle industry every year. According to the USDA, in 1995, calf death losses due to these diseases cost the industry $794 million. That figure did not take into account the significant losses incurred in treatment costs and decreased growth and feed efficiency when such problems strike.

While the ultimate goal of animal health researchers is to wipe out diseases, a more realistic objective is to at least reduce the severity of these illnesses. AAES researchers at Auburn University’s College of Veterinary Medicine may have found a way to achieve that objective, through the use of a common growth implant, Synovex.

In their studies, researchers discovered that pretreatment of calves with Synovex reduced the severity of the disease response in steers suffering from either experimentally induced coccidiosis, a severe diarrhea disease in cattle, or experimentally induced endotoxemia, a disease characterized by fever and reduced feed intake.

Researchers undertook two separate studies to determine whether anabolic implants, long used by the United States cattle industry to enhance the growth rate and feed efficiency of cattle, may also improve cattle health.

In the first study, Holstein steers were administered estrogen/ progesterone implants (Synovex C) at eight weeks of age. At 11 weeks of age, the steers were experimentally infected with Eimeria bovis, the organism that causes coccidiosis. The feed intake, weight gain, fecal consistency, rectal temperature, and blood indicators of inflammation were monitored for 28 days following E. bovis infection.

Photograph of two steers exposed to E. bovis (coccidiosis). The steer on the right was treated with Synovex C.

Figure 1. Effect of E. bovis (coccidiosis) on body weight in implanted and non-implanted steers. Coccidia = E. bovis infected; E2/P = estrogen progesterone implanted; * = differ from E2/P + coccidia steers.

The implanted steers that were infected with E. bovis had better feed intake than the steers that did not receive the implants, with implanted infected steers consuming on average 38% more feed than the non-implanted infected steers and having improved weight gain (Figure 1). In addition, the implanted group had less severe disease, characterized by only two days of fever, with a peak fever of 103.1 degrees Fahrenheit, versus five days of fever, with a peak of 103.64 degrees Fahrenheit, for the non-implanted steers. Furthermore, the implanted steers had five to six fewer days of diarrhea than non-implanted, infected steers.

Blood samples showed lower fibrinogen values (a general indicator of inflammation in cattle) in implanted, infected steers than in non-implanted, infected steers, indicating that infection with E. bovis, or coccidiosis, is less severe in steers receiving estrogen/progesterone implants than in non-implanted steers. Furthermore, among a control group of steers that were not infected with E. bovis, blood samples showed implanted steers had a greater number of immune cells than did steers that were not implanted.

In the second study, administration of estrogen/progesterone implants also was found to decrease the severity of experimentally induced endotoxemia. In this study, Holstein steers were administered estrogen/progesterone implants (Synovex S) at 20 weeks of age. Two weeks later, they were administered endotoxin, a bacteria cell wall component that causes fever and a loss of appetite. Feed intake, behavioral distress, blood indicators of tissue damage, and fever response to the endotoxin were monitored.

Figure 2. Effect of endotoxin on feed intake in implanted and non-implanted steers. EP = estrogen/progesterone implanted; * = differ from EP + Endotoxin treated steers.

Although fever response to endotoxin did not differ between implanted and non-implanted steers, other indices of the severity of disease were altered by implantation. Implanted endotoxin-treated steers had greater feed intake (2.1% of body weight) on the day of endotoxin treatment than non-implanted endotoxin-treated steers (1.1% of body weight; Figure 2).

Among the implanted steers, hyperglycemia was reduced following endotoxin and less fat was mobilized; concentrations of insulin-like growth factor-I were restored earlier; and concentrations of blood urea nitrogen were lower, indicating less tissue wasting. In addition, implanted steers infected with endotoxin had fewer signs of behavioral distress compared with the non-implanted group. These results indicate estrogen/progesterone implants reduce the severity of endotoxemia.

In summary, although all animals in the studies displayed clinical symptoms of the disease model, results indicate that estrogen/progesterone implants may reduce the severity of certain diseases in cattle. The results of these studies provide evidence of a previously unknown beneficial effect of utilization of estrogen/progesterone implants on the animals’ well being.

For more information, see Heath et al., American Journal of Veterinary Research, 1997, 58:891-896; and McMahon et al., Journal of Endocrinology, 1998, 159:469-487.