Because of drought...
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Vitamin & mineral deficiencies affect calf immune response |
Kay
Dee Feed REPORTS |
Reprinted from Tri-State Livestock
News By Troy Smith |
| It’s been a dry, stressful summer for many cattle producers in Tri-State country. Drought-stricken range and pastures played out early, while in hardest hit areas, the grass never really grew in the first place. Ranchers scrambled to secure extra hay or alternative feeds for their herds. In many cases, early weaning of calves was less an option than a mandate. And as producers prepared to pull calves from the cows, by picking up vaccines for immunizing calves, they often heard local veterinarians suggest that vitamin shots be included with preconditioning or weaning injections. |
| For along with severely limiting forage supplies, drought certainly compromises the quality of both grazed and harvested forages. Even the herds of producers having sufficient grass to squeak by, with cows holding their flesh and calves looking good, might be affected. Chances are that drought-stressed forages were lacking in nutrients, such as vitamins and minerals, that influence how an animal responds to infection by disease. And deficiencies in vitamins and minerals could jeopardize the immune response to calf vaccinations. |
| Vitamins are important, themselves, but also contribute to efficient use of other nutrients, including minerals. Vitamin A is likely to be of greatest practical importance to calves, because it affects vision, bone development and epithelial cell structure and maintenance. It is also believed to play a role in immune response. |
| "Vitamin A deficiency might be the biggest problem," states University of Nebraska Extension Veterinarian Steve Ensley. "Neither standing forage was stressed by drought, nor hay grown during drought are likely to contain much vitamin A. It’s the reason veterinarians have been asking clients to consider vitamin injections for calves. Most mineral supplement formulations contain vitamin A, but an injectable product is more efficiently utilized by the animal, than when delivered through the diet. And with an injectable, you know that every calf gets it." |
| Vitamin A doesn’t occur in plants as such, but forages do contain the precursor, carotene, that is converted to vitamin A in the body. Bleached pastures and hay produced during drought will be low in carotene. The liver can store vitamin A, but that capability is variable. Loss of stores often occurs during periods of dry, hot weather, when animals are consuming low quality feed, or have consumed feeds that are high in nitrate. According to Ensley, there is some evidence that supplemental vitamin A may help alleviate the toxic effects of nitrate in drought-stressed corn. |
| "Vitamin E is an antioxidant which helps counter the stress of weaning," adds Ensley. "Its boost to the calf’s immune system is analogous to the benefit humans might get from vitamin C. Vitamin E is thought help with the uptake of vitamin A, and it’s linked with utilization of the mineral selenium too. I’m a proponent. Even in a year with normal rainfall and forage growth, vitamin E at weaning is a good idea." |
| Most natural feeds contain vitamin E, but oxidation rapidly destroys it, so old hay or ground grains may be poor sources. |
| While many successful ranchers’ herds have exhibited acceptable overall performance with minimal mineral supplementation, other than sodium and chloride from salt, it is known that minerals play a major role in performance of range cows and calves. For most grazing and forage-fed cattle, phosphorus may be the only major mineral of concern, since most forages contain adequate to high levels of calcium and potassium and do not need to be supplemented. |
| According to the National Research Council, phosphorus requirements are highest for the beef cow at about 60 days after calving. Some research has shown that phosphorus supplementation is particularly beneficial during severe drought. |
| In calves, boosting potassium may help minimize the effects of stress. According to Ensley, some studies have shown that the potassium requirement of stressed calves is 20 percent higher than for non-stressed calves. He recommends supplementing the diets of just-weaned calves with potassium. |
| While limited research has been completed, trace minerals are believed to be important to immune response and disease resistance. Trace-minerals function primarily as catalysts for enzyme reactions within tissue cells, and deficiencies or imbalances may alter enzyme activity and impair immune function. |
| Colorado State University Extension Educator Terry Engle admits there has been little research to examine the influence of zinc deficiency in ruminant animals. However, numerous experiments with humans and laboratory animals have indicated that zinc deficiency reduced immune response. Zinc is an essential component of numerous enzymes involved in metabolism, cell repair and division, and vitamin A transport and utilization. |
| "Although the data is limited," offers Engle, "some research reported that increasing the level of supplemental zinc, from 30 to 100 mg/kg diet, tended to reduce morbidity from respiratory diseases in newly weaned and stressed calves." |
| Also required for enzymes related to an array of body functions is copper. Engle says copper’s role in immune response is certain, despite variable results from copper supplementation studies. Many factors can affect an animal’s response to copper supplementation, such as the duration and concentration of supplementation and the presence or absence of dietary copper antagonists in the environment. Even when copper is present in adequate amounts, the presence of excess sulfur, molybdenum or iron may inhibit the animal’s ability to utilize copper. |
| Chromium influences carbohydrate metabolism and protein absorption in mammals. Chromium supplementation of weaned, stressed calves appears to enhance antibody production to fight off some viral respiratory infections, while having little effect on others. Engle believes the type and degree of stress animals experience contributes to the variable findings. |
| "The interactions of trace minerals, immunology and disease resistance are extremely complex," explains Engle. "Despite the apparent involvement of certain trace minerals in the immune system, deficiencies of trace minerals have not always increased the animal susceptibility to infections. Factors that could affect response include environment (drought) and the stress." |
| Nutrition and stress are interactive and consequential. In other words, stress may produce or aggravate nutritional deficiencies and, nutritional deficiencies can produce a stress response. Drought-related nutrient deficiencies may combine with animal stress factors, including processing, crowding and transport that may accompany weaning, for a commulative effect. |
| "This certainly was not a ‘normal’ year. It’s likely that grazed and harvested forages are lacking in nutrients," warns Steve Ensley. "When supplementing, it’s best to check the NRC (National Research Council) requirements and follow recommendations." |
| For more information, consult Nutritional Requirements of Beef cattle, published by the National Research Council, by accessing the following website: http://stills.nap.edu/books/0309069343/html/ |
