Respiratory problems are one of the most common diseases in beef cattle and can cause slow growth rates, lower weaning weights and mortality in calves. In feedlot cattle, it is one of the most common causes of disease and can result in high costs of treatment and lower finishing weights and mortality.

Bovine respiratory disease (BRD) complex has many factors, including bacteria and viruses that can also impact reproductive performance, causing early embryonic death, abortions and congenital defects.

Infectious causes of BRD complex

Viruses

Viruses can cause primary disease like fever, listlessness and decrease in feed intake as well as damaging the lining of the airways and depressing the immune system. Some of the important respiratory viruses we think of can also cause other disease such as bovine viral diarrhea (BVD) and infectious bovine rhinotracheitis (IBR).

Many of the commercial vaccines have the “core” respiratory viruses like IBR, BVD, parainfluenza virus -3 (PI-3) and bovine respiratory syncytial virus (BRSV).

Bacteria

Bacterial pneumonia can either cause primary disease or secondary disease after the virus has damaged the respiratory lining and depressed the immune system.

Many bacteria that cause pneumonia can actually be found in the nasal passages of healthy cattle. Bacterial infections lead to similar clinical signs as viruses, with fevers, lack of appetite, weight loss, nasal discharge, coughing, difficulty breathing.

Antibiotics are effective for some bacteria, but bacteria that are part of the BRD complex can cause cattle to become very sick, cause chronic respiratory disease despite treatment and even cause death. Commercial vaccine products are available for control of these diseases.

When are cattle at highest risk for developing BRD?

High-risk periods of developing respiratory disease include times of high stress in calves, such as processing or weaning, weather extremes such as the hot days and cold nights in the fall, or during transportation.

Mixing animals from different sources may also result in exposure of naive individuals to different infectious agents or overwhelming their immune system when individuals are transported or confined in close quarters.

How can we reduce losses from BRD?

Vaccination can be an effective tool to help limit the amount of damage caused by the respiratory viruses that can set cattle up for nasty bacterial pneumonia while also addressing other reproductive and infectious disease.

Vaccines are not 100 percent effective; some may prevent disease, and some may only reduce the risk of clinical signs.

There are many different vaccination protocols that are influenced by whether or not the herd is open or closed, the risk of certain diseases in the geographic area and the different production classes.

It is best to work with your veterinarian or veterinary extension agent to come up with the vaccine protocol that best fits your herd and management.

With so many different products on the market, it can be confusing to know which products to use. Many of the commercial vaccines contain a combination of respiratory viral agents (BVD-1, BVD-2, IBR, BRSV, PI-3) and other agents that may influence reproductive performance (Campylobacter fetus and usually five serovars of Leptospira).

Vaccines can come in different forms, and it is important to know the difference, as they have different mixing, storage and directions for use.

• Modified live vaccines (MLV): These products contain inactivated virus that causes a low-grade infection to stimulate the immune system. There is a risk it can cause clinical disease and abortion in pregnant animals.
  
  Some products have been labeled as safe for use in pregnant or nursing animals, but always check the label directions first. MLV products can often cause a stronger immune response with only a single dose but require reconstitution of the vaccine and use within a certain period of time after reconstitution. Annual vaccination is recommended. It is important to vaccinate heifers and cows at least one month prior to breeding for maximum efficacy.
  
  
• Killed vaccines: These vaccine products contain only part of a virus or bacteria the immune system recognizes; however, these often need a booster four to six weeks later along with annual vaccination to maintain strong immunity.
  
  These products have low risk of causing clinical disease but may have a higher risk of causing an allergic or anaphylactic reaction.

Establishing a vaccine program

It is best to work with a veterinarian or extension agent to develop a vaccine protocol unique to each herd with respect to introduction of new animals, sharing perimeter fences with other cattle, as well as any historical herd health issues. The following are some general guidelines:

Breeding cows and replacement heifers

• Vaccinate six to eight weeks prior to the start of the breeding season with a combination vaccine (MLV or killed) that contains:
  
  
• BVD-1, BVD-2, IBR, BRSV, PI-3
  
  
• Campylobacter fetus
  
  
• Leptospirosis (five-way)
  
  
• Optional – killed bacterial products (Mannheimia haemolytica, Pasteurella multocida, Haemophilus somni)

(Cows can be given a killed product at pregnancy diagnosis to enhance the immune system and encourage colostral antibodies for passive immunity in calves.)

Bulls

• Vaccinate six to eight weeks prior to breeding at time of breeding soundness exam.
  
  
• BVD-1, BVD-2, IBR, BRSV, PI-3
  
  
• Campylobacter fetus
  
  
• Leptospirosis (five-way)
  
  
• Optional: Trichomoniasis, killed bacterial products

Calves

• Colostral immunity usually starts to decline around 3 months old. The first vaccines are recommended at time of processing or branding with a booster four to six weeks later at or around weaning.
  
  
• Clostridial vaccines (seven- or eight-way)
  
  
• BVD-1, BVD-2, IBR, BRSV, PI-3
  
  
• Replacement heifers also require brucellosis vaccination between the age of 4 and 12 months.
  
  
• Optional – Leptospirosis and killed bacterial products