Transition dairy cow diseases start their cascade before the cow ever gives birth. Keeping her immunological machinery in high gear before, during and after parturition is one of the key elements to heading off post-partum disease.
Trace nutrients are a critical component to the cow’s immune system — especially at this time. Bill Weiss, MS, PhD, The Ohio State University, says, “In ruminants, because of immunosuppression that occurs at parturition, antioxidants are extremely important during the transition period. Disease risk, especially infectious disease, is high during this period. However, disease can occur throughout lactation so proper supplementation of trace nutrients should occur throughout the life cycle of the cow.” Transition diseases such as metritis, retained placenta and mastitis all have multiple risk factors, and vitamins/trace mineral nutrition is only one. If producers are having a lot of infectious disease and/or retained placenta, they should look at trace mineral and vitamin nutrition to make sure they are at sufficient levels in the diet.
Not only does proper trace nutrient supplementation assist the cow’s immune system, but economically it proves beneficial. Prices vary but for a dairy cow it probably costs about $0.1 to $0.15/day to provide all necessary vitamins and trace minerals, according to Weiss. “One case of clinical mastitis costs between $100 and $150,” he says. “From all the economic analysis we have done, which only consider reduced cases of mastitis, proper supplementation of vitamins and trace minerals has a very positive return on investment.”
Though it’s always necessary for the bovine to have sufficient levels of trace nutrients, for vitamins in particular, it’s important their levels are adequate or even bumped up a few weeks before and after calving. “For trace minerals, because they are part of enzyme systems, I don’t think you need to bump them up, but you do need to make sure adequate levels are fed all the time,” Weiss suggests.
It’s not always easy to diagnose a trace mineral deficit via clinical signs or even diagnostic tests. Jerry Spears, PhD, North Carolina State University, notes that blood is not a reliable indicator of copper and zinc status unless the animals are severely deficient in the minerals. “Liver copper is a fairly reliable indicator of copper status,”
Don’t go overboard
Too much of a good thing can have detrimental effects, including overfeeding trace minerals. Weiss says excess vitamin A (below toxicity) can be fed and there is some data suggesting that these high levels interfere with vitamin E absorption. “Overfeeding of trace minerals are more likely a problem than overfeeding vitamins,” he notes. “High copper can cause toxicity and dead cows, and high Cu also is an oxidative stress. High selenium can increase oxidative stress and can also be toxic.”
Spears adds that there is some evidence that high concentrations of copper in the liver can cause liver damage in the absence of clinical signs of toxicity.
Although toxicity can occur for vitamins A and E, it is extremely rare. “In the real world, the cost of vitamin E keeps supplementation rates reasonable,” Weiss adds, so excess vitamin E supplementation is rarely a factor.
Weiss emphasizes that it is important to remember that vitamins and minerals will not fix bad conditions. “If cows are wallowing in slop, all the selenium and vitamin E in the world is not going to fix their mastitis problem.”
Trace nutrients and transition disease
Weiss and Spears offer this information on some of the roles vitamins and trace minerals play in dairy cow transition disease:
Vitamin E is an important lipid-soluble antioxidant that protects against free radical-initiated lipid peroxidation. Fresh green forage is an excellent source of vitamin E; however, concentrates and stored forages are generally low in vitamin E.
Dairy cows fed stored forages require approximately 1.6 IU of supplemental vitamin E/kg BW (approximately 80 IU/kg DM intake) during the dry period to maintain plasma alpha-tocopheral at concentrations (approximately 3 µg/mL) that maximize health and immune function. “This amount of E probably will not maintain plasma E concentrations right around calving,” Weiss notes. “It takes between 2000 and 5000 IU/day to do this.” He adds that 80 IU/kg is probably OK for most of the dry period, but starting a few weeks before calving it is not enough.
The major impact of vitamin E on immunity appears to relate to enhanced neutrophil function. Rapid recruitment of neutrophils is critical for maximizing host defense mechanisms. Supplementation of 3000 IU of vitamin E/day during the transition period prevented a decline in neutrophil superoxide anion production and interleukin 1 (IL-1) production after parturition compared with control cows not supplemented with vitamin E.
Incidence of retained placenta has been reduced by oral or intramuscular administration of vitamin E but responses have been variable. One study found that IM injection of 3000 IU of vitamin E pre-partum reduced the incidence of metritis as well as retained placenta in dairy cows.
Selenium (Se) functions in the antioxidant system as an essential component of a family of glutathione peroxidase enzymes. Selenium deficiency in dairy cows can reduce the ability of blood and milk neutrophils to kill bacteria. Dietary Se can also affect cell-mediated immunity in dairy cows.
Studies have indicated that pre-partum Se supplementation can reduce the incidence of retained placenta in dairy cows fed diets low in Se. It was also found that oral Se supplementation was as effective as IM administration of Se and vitamin E in preventing retained placenta in cows fed Se-deficient diets.
Copper (Cu) is involved in the antioxidant system via its involvement in the enzymes Cu-Zn super-oxide dismutase and ceruloplasmin. Ceruloplasmin is an acute phase protein that increases during disease and may be important in scavenging superoxide radicals. Copper deficiency in cattle is generally due to the presence of dietary antagonists such as sulfur, molybdenum and iron that reduce Cu bioavailability.
Dietary Cu affects phagocytic as well as specific immune function. Heifers fed diets marginal in Cu (6–7 mg/kg diet) had a greater percentage (60% vs. 36%) of infected quarters at calving than heifers supplemented with 20 mg Cu/kg diet.
NRC requirements for chromium (Cr) in dairy cattle have not been defined. Some studies indicated that chromium (Cr) can significantly affect feed intake and milk production in early lactation dairy cows (Cr supplemented from 21–28 days pre-partum until 28–35 days postpartum).
Studies in periparturient diary cows indicate that Cr supplementation may affect cell-mediated and humoral immune response.
Zinc (Zn) has an antioxidant role and also may affect immunity via its important role in cell replication and proliferation. Zn deficiency impairs immune responses and reduces disease resistance. Plasma Zn concentrations decrease in dairy cows at parturition and return to baseline values within three days.
ß-Carotene is the major precursor of vitamin A and occurs naturally in feedstuffs. It may affect immune functions, and carotenoids without vitamin A activity have been found to enhance immune response. Supplementation of periparturient cows with 300 or 600 mg ß-carotene/day enhanced lymphocyte proliferation induced by mitogen stimulation before an dafter parturition.
In one study supplementation of ß-carotene (300 or 600 mg/day) or vitamin A (120,000 IU/day) significantly reduced incidence of retained placenta compared to control cows. Incidence of metritis was significantly reduced by ß-carotene but not by vitamin A supplementation.
For more information, read Spears, J.W., Weiss, W.P., “Role of antioxidants and trace elements in health and immunity of transition dairy cows,” The Veterinary Journal April 2008, www.sciencedirect.com.