Emma Reints, ISU Animal Science Graduate Research Assistant, Iowa Beef Center
Vitamin A is essential for reproduction, growth, and health in cows. Green grass is rich in beta-carotene, a precursor of vitamin A, but recent droughts may lead to vitamin A deficiency. National recommendations for vitamin A supplementation require that cows eat plenty of green grass for a significant part of the year, build reserves for important processes such as vision, maintain cow health during pregnancy, and support cows’ general health. The premise is that we support the maintenance of good health. It is essential to monitor for signs of vitamin A deficiency, as vitamin A deficiency can be a major factor in the success of this year’s calf crop.
Young calves with vitamin A deficiency show signs ranging from weakness to weakened immune systems and are more susceptible to disease, especially diarrhea. Vitamin A is important in epithelial cells, such as those in the eyes and the lining of the intestines. Signs to look for include:
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Increase in illnesses such as diarrhea and pneumonia
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Reduced feed intake and growth
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In extreme deficiency, a white film forms on the eyes (xerophthalmia)
Obtaining colostrum is one of the most important parts of establishing the vitamin A status of newborn calves. Did you know that a newborn calf has very little vitamin A in its body? Although vitamin A cannot be transferred to the calf in the womb, colostrum is rich in vitamin A and establishes stores of vitamin A in the newborn calf. It is important to consider supplementing the cow with vitamin A during late pregnancy, as vitamin A stores begin to be mobilized for colostrum production before calving. Preserved feeds such as cornstalks and hay are likely to be low in vitamin A, so supplementation with vitamin A is necessary to ensure calves receive adequate vitamin A from colostrum and milk.
Given the ongoing drought in Iowa, current vitamin A recommendations are considered low and producers should use 75,000 IU/kg if their cows are considered to have sufficient vitamin A reserves. You may want to aim for vitamin A per day, or closer to 90,000 IU/day if you are feeding dairy cows. (Mary Drewnoski, UNL, personal communication) Remember, vitamin A breaks down easily over time. , meaning that if you give older supplements you won’t get the vitamin A listed on the label and may not have enough to support you. Cow and calf health.
If unfortunately a calf is stillborn or dies, diagnostic tests should be performed to find out if vitamin A deficiency is a concern. Producers must also inform the laboratory whether the calf has colostrum so that appropriate reference ranges can be used for diagnosis.
If you have been diagnosed with vitamin A deficiency, vitamin A injections may be an option to rapidly increase your vitamin A status.
