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Supplementing Vitamins A and E During Drought
USAgNet - 07/26/2016

Producers grazing livestock this summer should consider supplementing vitamins A&E due to drought conditions, said Alvaro Garcia, SDSU Extension Agriculture and Natural Resources Program Director & Professor.

"Both vitamins are typically present in green forage, however when most of the diet consists of dry summer pasture or dry, bleached hay, deficiencies in both vitamins is likely," Garcia explained.

Essential to maintaining early pregnancy (pro-vitamin A or beta carotene) and immunity, specifically helping ward off pink eye (E), if these vitamins are not available through grazing, Garcia encourages livestock producers to consider supplements that contain them.

"When facing a drought, one usually thinks first about forage and water shortages, however there are other highly essential nutrients that may be critically short under these conditions. Reduction in the fat-soluble vitamins, such as A & E usually poses a problem," he said.

He added that other drought-related stressors, such as aflatoxins in supplemental feed and reduced water quality, can also deplete livestock's stores of A&E.

Garcia is not worried about vitamins D and K, which are two other fat-soluble vitamins, because they are readily synthesized through sun exposure and gut microbes.

What role do vitamins A & E play?

Vitamin A: Vitamin A is critical to many functions in the body, particularly the surfaces (epitheliums) of many body systems. As such, it plays a critical role in vision, growth, and reproduction (embryonic development).

Vitamin A deficiency has also been associated with abortions, retained placentas and compromised immune function, as well as an increase in the number of sick (morbidity) and dead calves.

In cows supplemented with vitamin A or beta carotene as provitamin, pregnancy rate doubled particularly in the second and third cycles (22 percent versus 11 percent).

Cow/calf pairs challenged by the environment either by disease or other stress, with no enough green pasture, rely on the vitamin A stored in their liver or the one supplied with the minerals for their protection. If they haven't been supplemented or they are not fed green forages their reserves may last up to 180 days. It is thus critical to consider what did cows eat last grazing season, and what were they supplemented with during the past winter. Vitamin E: Vitamin E helps maintain the integrity of the keratin, and as such it helps protect the eyes from pinkeye, a common problem oftentimes also observed during the summer.

This vitamin helps maintain the integrity of the cell membrane and is essential in boosting the immunity. Around calving time for example, high levels of this vitamin have been associated with boosting white blood cells necessary to fight infections. As a result of their antioxidant properties, both vitamin E and selenium prevent cell and tissue damage protecting from the invasion of pathogens.

When purchasing mineral supplements, Garcia encourages producers to verify that they contain adequate concentrations of vitamins A and E. It is advisable that trace mineral tubs or licks for cows with their calves contain 500,000 international units (IU) of vitamin A and 50 of vitamin E. This is particularly critical when pastures are dry and bleached, a clear sign the vitamins have been oxidized.

Depending on its quality, Garcia said that some baled forages will contain percentages of vitamins A & E, so if livestock producers are supplementing with baled forages. The greener these forages are (for example alfalfa blends) the greater their concentrations in provitamin A and vitamin E.


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