Too little Vitamin A
Vitamin A is required for normal vision, for the skin and other epithelia, and bone formation.
Vitamin A deficiency may lead to poor vision at dusk and during darkness, runny eyes, weak and scaly skin, loss of appetite, reduced growth rate, poor conception rates and general weakness.
Solutions: Concentrates and most vitamin/mineral mixtures for horses contain ample amounts of vitamin A. Cod liver oil, carrots, green grasses, haylage and well cured hay are all good sources of vitamin A. #Grasses and haylage also contain beta-carotene which forms vitamin A in the body.
Too much Vitamin A
Vitamin A if found in two forms: retinol and betacarotene. Betacarotene is a precursor for vitamin A and is present in grasses and other feeds which contain red or yellow pigments.
During normal feeding conditions the risk for toxicity from betacarotene is low, since it is not all absorbed from the diet.
Grasses, haylage and carrots are feeds which contain high amounts of betacarotene. When using such feeds you may experience red lines for Vitamin A.
If a major part of vitamin A in the diet comes from such betacarotene-rich feeds you can accept the ration even when the line showing vitamin A is red.
The center window on the help screen gives an analysis of the relative contribution of the different feeds to the total intake of vitamin A.
Prolonged over feeding of vitamin A will lead to intoxication resulting in weak or abnormally formed bones, hair loss and abnormal skin.
Solutions: Give supplements which contain less vitamin A. Substitute commercial (vitamin-fortified) concentrates with grain. Be careful of giving more than one vitamin/mineral mix as many will contain vitamin A.
Do not give cod liver oil if the ration already contains a lot of vitamin A.