Vitamin A is a generic term that encompasses a number of related compounds that are essential fat-soluble molecules, predominantly stored in the liver. Vitamin A comes from two sources. One group, called retinoids, comes from animal sources and includes retinol. The other group, called carotenoids, comes from plants and includes beta-carotene. Vitamin A has important roles in several different body functions. These include:
- Embryonic development
- Organ formation
- Normal immune functions
- Maintenance and integrity of the mucous membranes, skin, remodeling, and growth of bones
- Eye development and vision
- Maintaining the stability of cell membranes and nerve sheaths
- Synthesis of adrenal cortical hormones (corticosterone)
- Regulation of thyroxin output
- Manufacture of red blood cells
Vitamin A Deficiency in Ducks
Since vitamin A is used by multiple systems throughout the duck’s body. The associated clinical signs vary depending on the system affected. For example, since the duck’s oral cavity and sinus are lined by mucus membranes, if these areas aren’t receiving adequate amounts of vitamin A, then the protective lining may begin to erode, causing white plaques on the roof of the mouth or base of the tongue. Defects in growth and differentiation of epithelial tissues, frequently resulting in keratinization. Keratinization of these tissues results in loss of function in the alimentary, genital, reproductive, respiratory and urinary tracts.
Risk Factors for Vitamin A Deficiency
Causes of vitamin A deficiency include inadequate intake of the vitamin from the diet, impaired absorption or storage, and poor conversion of carotene to active vitamin A. Vitamin A deficiency occurs in malnourished and chronically sick ducks that are not provided any access to fresh green forage or other foods containing high levels of vitamin A. List of factors with onset of vitamin A in ducks include:
- Malnourished or starved ducks.
- Feeding ducks feed which has been stored for longer than 60 days.
- Lack of access to fresh forage.
- Coccidiosis - Causes destruction of vitamin A in the gut but also injures the microvilli of the intestinal wall.
- Intestinal parasites (roundworms, tapeworms, flukes)
- Vitamin imbalances
Vitamin A deficiency is often seen in heavily parasitized animals that supposedly were receiving an adequate amount of the vitamin.
Nutritional Recommendations for Vitamin A in Ducks
Nutritional vitamin A requirements in Pekin Ducks at various ages include:
Table 1: Duck Vitamin A Requirements
|Age Range||Vitamin A (IU)|
|0 to 7 weeks||8,000|
|7 to 20 weeks||5,000|
|Older than 20 weeks||10,000|
Vitamin A requirements are higher under stressful conditions such as extremely hot weather, viral infections, and altered thyroid function.
Complications of Vitamin A Deficiency
Ducks with a vitamin A deficiency have an increased susceptibility to infections, especially bumblefoot