Immune Booster

Gaining Ground in the Fight Against Shipping Fever

Victoria G Myers
By  Victoria G. Myers , Progressive Farmer Senior Editor
New treatment for Bovine Respiratory Disease (BRD) is an alternative to traditional antibiotic therapies. (DTN/Progressive Farmer photo by Jim Patrico)

As the cattle industry responds to consumer demand for less antibiotic use, a new tool for control of bovine respiratory disease (BRD) in young cattle is making its mark.

Zelnate is novel, nonantibiotic technology that enhances an animal's immune system, boosting its ability to naturally fight BRD. The product, from Bayer Animal Health, is the first licensed immunostimulant in cattle and has a 21-day withdrawal period -- the shortest such period granted by the FDA. It was released in August 2015.

BRD, also known as "shipping fever," is common in the U.S., with 16.2% of all cattle treated for the disease. Cattle mortality to BRD is reported at 40%. The bacteria most commonly associated with BRD in cattle is Mannheimia haemolytica. Affected cattle often have bacterial lung infections, and permanent lung damage in survivors is common.

Lung Lesions. In a comparison of 3- to 4-month-old steers treated with Zelnate (2-ml dose) or a placebo, the average lung lesions on Day 5 were nearly halved in the Zelnate group (6.3 versus 12.1%). These lung lesions have been shown to reduce average daily gains. As a result, market values of cattle with lung lesions are reported to average as much as $77.07 per head less than those without.

Reduced Mortality. Another comparison of 3- to 4-month-old steers looked at whether Zelnate could reduce mortality in cattle infected with Mannheimia haemolytica when compared to a placebo treatment. Twenty-four hours after infection, morbidity was at 67.5% across both groups. Over five days, mortality in the placebo treatment group was at 20%; in the Zelnate treatment group, it was 2.5%.

Antibiotic Comparison. After Zelnate was approved by the FDA, James Little, senior technical veterinarian with Bayer Animal Health, said a field study was performed involving medium-risk cattle on arrival in a feedyard situation. The calves had been shipped and commingled. Their stress and exposure to pathogens were what would be considered typical, Little said, for ranch-origin cattle.

"We wanted to see if Zelnate could perform as good as an antibiotic if given to calves on arrival for control of BRD," he explained. "We wanted to manage or decrease the number of calves that would develop BRD."

The antibiotic the comparison was made against was Micotil (2-ml dose), typically given for control of BRD in stressed calves. The goal was to see if Zelnate could get within 10% of the control of Micotil. The trial was a success, with morbidity at 13.8% for Zelnate versus 7.65% for Micotil -- a difference of 6.15% and well within the goal.

Overall, BRD mortality for the Zelnate group was 0.50%; for the Micotil group, it was 0.44%. Average daily gains for the Zelnate group were 2.91 pounds per day versus 2.96 pounds per day for the Micotil group.

Little said producers using Zelnate are generally opting for one dose on arrival in low- and medium-risk cattle. For high-risk cattle, he adds, they are often using it in conjunction with an antibiotic. High-risk cattle are generally considered to be those sold through auction barns and/or shipped long distances prior to arrival at feedyards.

Zelnate is sold in three dose-size packages: 5, 10 and 50. Cost per treatment varies with the dose-size package purchased but, on average, ranges from $12 to $14. The product must be refrigerated and mixed and administered per manufacturer directions. For more specific information, visit


Victoria Myers