VITAMIN A ACTIVITY OF FERMENTATION BETA-CAROTENE FOR SWINE

Meeting the Vitamin A Requirement: The Efficacy and Importance of β-Carotene in Animal Species

Vitamin A is essential for life in all vertebrate animals. Vitamin A requirement can be met from dietary preformed vitamin A or provitamin A carotenoids, the most important of which is β-carotene. The metabolism of β-carotene, including its intestinal absorption, accumulation in tissues, and conversion to vitamin A, varies widely across animal species and determines the role that β-carotene plays in meeting vitamin A requirement. This review begins with a brief discussion of vitamin A, with an emphasis on species differences in metabolism. A more detailed discussion of β-carotene follows, with a focus on factors impacting bioavailability and its conversion to vitamin A. Finally, the literature on how animals utilize β-carotene is reviewed individually for several species and classes of animals. We conclude that β-carotene conversion to vitamin A is variable and dependent on a number of factors, which are important to consider in the formulation and assessment of diets. Omnivores and herbivores are more efficient at converting β-carotene to vitamin A than carnivores. Absorption and accumulation of β-carotene in tissues vary with species and are poorly understood. More comparative and mechanistic studies are required in this area to improve the understanding of β-carotene metabolism.

Inhaled feed particles in experimental pigs with and without vitamin A deficiency

An attempt was made to experimentally reproduce an unusual respiratory disease of pigs fed a dusty mixture of finely ground peas, wheat, and barley. Groups of vitamin-A-deficient piglets from this herd were either given dry feed and daily exposure to dust from the feed or were given wet feed. Vitamin-A-fortified pigs of another stock were also given the dry feed and dust exposure. The upper and lower respiratory tracts, renal pelves, and interlobular ducts of salivary glands were studied histologically. The distinguishing features of lungs were starch particles from feed (up to 31.2 mum in diameter) in all lungs (but more in lungs of pigs given dry feed), free alveolar macrophages, giant cell formations, and mild degenerative processes of respiratory epithelium. The epithelium of most renal pelves was marked by mucinous degeneration.