Vitamin A Deficiency
Vitamin A is one of the most overlooked and underestimated vitamins for cattle and sheep, especially in the autumn/winter period, and at calving/lambing. Vitamin A is important for the function of the immune system, the health of epithelial tissues, mucous membranes, the eye, and the central nervous system. It is also important for reproductive performance, and normal bone growth and development of calves and lambs.
Vitamin A deficiency causes the protective functions of cells in the digestive, respiratory, urinary, and reproductive tracts to break down. This leads to a higher susceptibility to infections of the gut, respiratory, and eye tracts. Marginal Vitamin A deficiencies in calves cause lower responsiveness of immune cells in the body and a breakdown of the protective functions in the eye, gut, and lungs.
The importance of this vitamin to the newborn calf is worsened by the fact Vitamin A does not cross the placenta in high enough amounts to meet newborn requirements. Calves and lambs must obtain sufficient levels through colostrum right after they are born. This means producers should focus on the vitamin status of the cows/ewes prior to giving birth to ensure sufficient levels in the colostrum.
Pink Eye is also known as infectious kerato conjunctivitis (IKC). This involves inflammation of the cornea (keratitis) and the eyelids (conjunctivitis). The classical form of Pink Eye is infectious in nature and is caused by Moraxella Bovis in cattle, with flies acting as transport vectors, hence it tends to be a warm weather condition. Other types of ocular problems can occur at any time of the year due to a variety of causes. Vitamin A is a key vitamin in the maintenance of healthy vision and deficiency of Vitamin A can cause night blindness, or predispose to other infectious eye conditions, because of its effects on immunity. Vitamin A deficiency tends to occur late in the season in cattle and sheep, when green herbage full of beta carotene (the precursor of vitamin A) is in short supply. Stored forage is much lower in beta carotene content than grass.
Some trace mineral /vitamin deficiencies in cattle have been linked to reduced immune responsiveness and might also lead to elevated rates of pink eye. (Vit E, iodine) When it comes to pinkeye prevention, maintaining adequate levels of Vitamin A, beta carotene, copper and selenium is particularly important.
Dietary Sources of Vitamin A.
Plants contain chlorophyll and carotene pigments. The greener the plant (chlorophyll), the more carotene it contains also. Beta Carotene is a precursor of vitamin A. and cattle/sheep manufacture vitamin A in the rumen from the carotene they consume in plants. Fresh green herbage contains excessive amounts of beta carotene, and the greenness of the forage generally gives an approximate indication of carotene content. Vitamin A deficiency is rarely seen in pastured cattle for this reason.
Cattle convert yellow and green pigments (carotene) from plants into vitamin A. Carotene is in all green plants and is particularly plentiful in fresh, leafy forage, but is not found in high concentrations in many concentrate feeds. Concentrates and, hay and silage can be quite low in carotene content, and the storage conditions of the fodder and ensilage procedures may deplete content further. In addition, carotene is an antioxidant and readily combines with oxygen and thus it can be degraded quite rapidly on storage. Hence there is quite a contrast between the carotene content of lush grass herbage in summertime, and the carotene content in concentrates, hay, or silage over the autumn /winter period. For his reason Vitamin A supplementation is vital for animals over the autumn /winter period because the vitamin A precursor (beta carotene) is in short supply in the forage. The classic sign of vitamin A deficiency in cattle is night blindness (difficulty seeing in dim light) with total and permanent blindness possible in younger animals, and blindness in calves born to deficient dams. Excessive tearing (watery eyes) in cattle also occurs.
Vitamin A Storage in the Body
Cattle and sheep cannot generate their own Vitamin A, they need to eat green plants containing carotenoid precursors such as β-carotene – found in the orange-yellow pigments in the green leaves of plants. The cattle and sheep then convert the β-carotene to vitamin A in the wall of the small intestine.
Vitamin A is a fat-soluble vitamin and is stored in the liver, with lesser amounts in other tissues and organs. Cattle /sheep can store vitamin A for 3 months in the liver. When adequate green feed is available, cattle and sheep meet their daily requirements, and can store excess Vitamin A in their liver. When the diet is deficient in the carotenoid precursors, Vitamin A is released from the liver to meet daily needs. When the liver supply is exhausted, vitamin A deficiency occurs.
Feed /Forage Problems for Vitamin A
Stored fodder such as hay that has been stored for extended periods, or exposed to sunlight or heat, has greatly decreased amounts of β carotene. Similarly, mineral mixes and processed feeds including vitamin A that have been stored for extended periods also have lowered levels of vitamin A, as the vitamin degrades over time.
Vitamin A is considered by many to be the most important vitamin regarding the need for supplementation. Vitamin A is necessary for proper bone formation, growth, appetite, muscle development, energy metabolism (glucose synthesis) and skin and hoof tissue maintenance, as well as vision. The vision function is associated with visual purple in the eye when animals are trying to adapt from light to dark.
ProVitaMin drench from Provita is High in Vitamin A
Approaching the end of season, when most cow herds will be receiving rations composed of low carotene forages, vitamin A supplementation is one of the fist items to consider when planning an appropriate diet. Provitamin drench from Provita contains 5 million units of Vitamin A and is a particularly useful Vitamin A supplement. It also contains many other minerals and vitamins such as selenium, vitamin E, iodine, and cobalt, all of which are key nutrients for reproductive functioning, and protection against metritis and mastitis in the post partem period. Routine dosing over the summer and housing period with Provitamin drench will ensure optimum reproductive, transition, digestive and post partem functioning.
- Provitamin Drench is adequate in Vitamin A supplementation for cattle
- Provitamin Drench for cattle contains 5,000000 IU of Vitamin A per litre
- The adult cattle dose is 50 ml, so each dose delivers 250,000 IU Vitamin A
- Cows need 30,000 to 50,000 IU Vitamin A per day
- The normal Vitamin A requirements are 50,000 IU per 500 kg lactating cow…. A little lower in other animals
- Hence the Provitamin dose delivers approx. 5 times the usual daily requirement
- ProVitaMin contains over 25 active constituents with elevated levels of Vitamin A, Vitamin E, Selenium Copper, Cobalt & Ascorbic acid