THE COLOSTRUM COUNSEL - Colostrum-Derived Immunity Against Common Respiratory Viruses in Calves
An important factor in calf hood health is the presence of maternal antibodies in calf serum during the critical first few weeks of life for protection from disease. One study shows that compared to maternal colostrum, feeding a lacteal-derived colostrum replacer provides a more uniform range of antibody titres to some common respiratory viruses affecting calves. Feeding a colostrum replacer may allow for better prediction of vaccination schedules and reduced incidence of disease in a herd.
Bovine respiratory disease (BRD) is one of the most important diseases affecting cattle in North America and is an important cause of economic losses in cattle operations worldwide. It is estimated that economic losses due to morbidity and mortality associated with BRD in the beef industry in the United States can reach US $800 to $900 million per year. Viral respiratory pathogens such as bovine viral diarrhea virus 1 and 2 (BVDV 1 and BVDV 2), infectious bovine rinotraqueitis (IBR), bovine respiratory syncytial virus (BRSV), and parainfluenza-3 virus (PI3V) play an important role in the pathogenesis of BRD due to their ability to impair the integrity of the upper respiratory tract, cause immunosuppression, promote secondary bacterial infection, and cause acute clinical disease. Antibodies against respiratory viruses transmitted through maternal colostrum protect calves against acute BRD and calves with high serum antibody titers against BVDV, IBR, BRSV, and PI3 are protected against developing acute BRD at challenge with viral pathogens; however, as colostrum-derived immunity wanes, calves become susceptible to acute BRD. The duration of colostrum-derived immunity against respiratory viruses depends directly on the amount of specific antibodies to BVDV, BHV-1, BRSV, and PI3 ingested and absorbed from maternal colostrum. The higher the levels of antibody absorbed from colostrum, the longer the duration of the maternally-derived immunity and the longer the protection against these pathogens. Interestingly, a high variation in the initial serum levels of antibodies against respiratory viruses is observed in calves that receive maternal colostrum at birth. Usually proper amounts and quality of maternal colostrum provide enough immunoglobulins to prevent failure of passive transfer in newborn calves but unfortunately that does not always translate into transfer of adequate levels of virus-specific immunoglobulins. This phenomenon leads to uncertainty and variability of the age at which calves will become susceptible to BVDV, BHV-1, BRSV, and PI3 infection and makes the establishment of adequate vaccination programs more challenging (Figure 1).
|Figure 1. Proportion of calves that become susceptible to acute BVDV infection (AB titer < 1:32) per time period. A high percentage of calves fed MC were susceptable to acute BVDV-2 infection in the pre-weaning period, whereas CR calves were protected until 4-5 months of age and could potentially respond to vaccinations in a uniform way.|
Colostrum replacement products provide newborn calves with adequate amount of immunoglobulins and prevent failure of passive transfer when the availability and quality of maternal colostrum on the farm are limited. In one of our recent studies [Chamorro MF, Can J Vet Res 2014; 78(2):81] we compared the serum levels and the duration of BVDV 1, BVDV 2, BRSV, IBR, and PI3V antibodies in calves fed maternal colostrum (MC) or a SCCL colostrum replacement (CR) at birth. The results of this study demonstrated that calves that received CR had greater BVDV 1 and BVDV 2 serum antibody titers during the first months of life. Additionally, the levels and duration of immunity against BVDV, IBR, BRSV, and PI3 were uniform and consistent in calves that received CR at birth. In contrast, calves that received MC demonstrated highly variable levels and duration of immunity against the same viruses which resulted in shorter times to reach sero-negative status and to become susceptible to acute infection. The greater variability in levels and duration of immunity observed in calves that received MC at birth could increase the risk of introduction of infectious pathogens such as BVDV, BRSV, BHV-1, and PI3V into the calf-herd. On the other hand, consistent levels and duration of immunity against respiratory viruses provided by SCCL colostrum replacement products reduce the risk of introduction of viral respiratory pathogens into the calf-herd and facilitate prediction of optimum time to vaccination.
DVM, PhD, DACVIM - Technical Veterinary Consultant, SCCL and Assistant Professor of Livestock Medicine and Field Service, College of Veterinary Medicine, Kansas State University