Recognize disease challenges among young dairy heifers, know when they occur and then increase the resistance and/or reducing the challenge.
By Tom Van Dyke, DVM, Manager of Veterinary Services, Merial
A “perfect storm” is an expression that describes an event where a rare combination of circumstances will come together to impact a situation drastically.1 An outbreak of respiratory disease in a group of young dairy heifers is just such a situation: The challenge, or exposure to the pathogen, increases at a time when resistance and immunity are compromised.2
Unfortunately, this combination of disease challenge and aggravating circumstances is not rare.Avoiding the perfect storm includes recognizing the disease challenges, knowing when they occur and then increasing the resistance and/or reducing the challenge.
One of the first times a perfect storm may occur comes at weaning when calves are grouped for the first time. Passive immunity acquired from colostrum has waned to a low point, and the calf’s own immune system is not yet fully responsive.3,4 During this time, these calves may be exposed to others harboring viruses through calf-to-calf contact or crowding. Continuous use of facilities also increases the number of pathogens in the environment. Other factors to consider are environmental stressors, such as temperature fluctuations, drafts and noxious gases such as ammonia, and exposure to internal and external parasites, which can reduce resistance and an animal’s immune response. Comingling and socializing with other calves is another stress.
Minimizing or eliminating predisposing factors and enhancing immunity with timely vaccinations are obvious first steps in preventing respiratory disease. However, working beyond that early intervention is essential. Astute heifer raisers are able to recognize situations in which respiratory disease is likely to occur and may choose to treat the whole group of susceptible calves with an antimicrobial in the face of an outbreak or when circumstances are aligning for a perfect storm.
Early detection, isolation and appropriate treatment of sick animals are also critical.4 Once a single immune-deficient animal develops disease, it can become a multiplier of pathogenic bacteria, shedding/spreading in sufficient numbers to overwhelm the defenses of healthy calves. These newly infected calves then become multipliers and a herd outbreak is underway. To help with early detection of respiratory disease and, thus, prompt intervention, try using the scoring chart available at http://www.vetmed.wisc.edu/dms/fapm/fapmtools/8calf/calf_respiratory_scoring_chart.pdf.
The choice of antimicrobial and timing of its use will be specific to the operation’s resistance level and challenges. The antimicrobial used for either control or treatment should ideally be proven effective against the likely respiratory pathogens, have a rapid response and prolonged efficacy.
©2011 Merial Limited, Duluth, GA. All rights reserved. RUMILGN1167 (10/11)