Veterinarians understand that consumption of an adequate amount of good-quality colostrum is vital to providing calves with antibodies that protect them against infectious disease during the first few months of life. It appears that other factors in colostrum are also important for helping the calf develop its own immune response to immune challenges, including vaccination.
Adequate levels of fat-soluble vitamins such as vitamin A and E are necessary for a normal immune response to vaccination or infection. “Fat-soluble vitamins such as A and E do not cross the placenta well, but they are present in high concentration of colostrum from cows that have been consuming diets sufficient in these nutrients,” says Amelia Woolums, DVM, MVSc, PhD, DACVIM, DACVM, University of Georgia. “Calves that do not ingest an adequate volume of good-quality colostrum will begin life deficient in these vitamins, which will make them unable to respond properly to vaccination as long as the deficiency persists.”
Maternal cells that are present in colostrum may also help stimulate the calf’s immune system and improve response to vaccination and other immunological stimuli. Neonatal animals of many species have been shown to absorb live maternal cells in colostrum (primarily monocytes and lymphocytes). “Research has shown that immune cells from calves receiving colostrum containing maternal cells more rapidly developed the capacity to ‘present’ antigen,” Woolums explains. “The calves’ own immune cells were more quickly able to initiate an immune response to foreign substance.” They also showed evidence of presenting antigen within a week after birth, in contrast to calves that received colostrum from which cells had been removed, which were only able to present antigen at two to three weeks after birth (AJVR 66:1854, 2005).
Woolums notes another study showing that cells from calves receiving fresh colostrum containing maternal cells responded to stimulation with bovine viral diarrhea virus (BVDV) by 24 hours after birth (AJVR 68:778, 2007). “Although the responses to BVDV did not persist for more than a few days, they may have induced a chain reaction of immune stimulation that could have improved response to vaccination, if it had occurred,” Woolums says. These studies provide evidence that live maternal cells in colostrum can stimulate and perhaps improve a calf’s immune response if it is exposed to immunological stimuli such as vaccination or infection, although much is still not known about their effects.
Feeding good-quality frozen colostrum is sometimes done to provide a calf with an optimal amount if its dam’s colostrum is inadequate. However, frozen colostrum will not contain live maternal cells. “We don’t have enough information to say if it’s better for a calf to get frozen colostrum with a good level of antibody but no living cells, or fresh colostrum with a suboptimal level of antibody but live cells,” Woolums says.
“For now, because so much research has shown the benefit of providing calves colostrum with a good amount of antibody, it’s probably best to stick with the better-quality frozen colostrum, if that is the only way to provide a calf with colostrum containing a sufficient level of antibody. However, if fresh good-quality colostrum can be given, we now know that the live cells in the colostrum induce changes in the calf’s immune system that may lead to better response to vaccination and better pro-tection against disease.”
Woolums adds that other factors in colostrum such as lactoferrin may play a role in preparing the calf’s immune system to respond to vaccination or other immunologic stimuli, but more research is needed in this area.
Nutrition’s effect on calf immunology
Aside from fat-soluble vitamins, animals deficient in minerals such as zinc, selenium, copper and chromium have suboptimal immune responses to vaccination and other immunological stimuli. Stud-ies have evaluated the effect of supplementing diets with various vitamins and minerals to improve immunity and disease resistance in cattle. “In general, providing levels of vitamins and minerals in ex-cess of what calves require has not consistently proven to improve immune response or disease re-sistance in a clear way,” Woolums says. “However, supplementation of animals that are deficient does improve immunity and resistance to disease.”
Calves fed diets deficient in protein and energy also have suboptimal responses to vaccination and other stimulation of the immune system. “Some producers have been feeding dairy calves on ‘intensi-fied’ schedules that provide relatively more energy and protein than was historically fed to calves,” Woolums says. Research by scientists at USDA-ARS and Cornell University showed that immune cells from calves fed an intensified milk-replacer diet produced less interferon gamma and more nitric oxide in response to immunologic-stimulation than did cells from calves fed a diet lower in energy and protein (J Dairy Sci 86:3592, 2003).
“Gamma interferon and nitric oxide are important mediators of immune responsiveness, particularly cell-mediated immune responses,” Woolums explains. “While this research showed that dietary en-ergy and protein appeared to have an effect on some aspects of the immune response, more re-search is needed before we know the importance of any effect intensified diets may have on the re-sponse post-vaccination or infection.”