Chromium nutrition of livestock species.
2005
Hayirli, A.
Chromium has received much attention in nutrition research following the elucidation of its role in metabolism. The Cr content of foods and ability to augment the action of insulin are highly variable. In general, Cr from brewers' yeast, meat and kidney, and unrefined grains has high biological activity. Chromium absorption occurs mainly in the small intestine. Carried in the blood bound to plasma proteins, it is transferred to tissues via transferrin. Inorganic forms are mostly excreted via the faeces, whereas organic forms are excreted mainly via the urine. Chromium is an essential mineral for humans and laboratory animals, but not for livestock animals. Chromium is a part of the glucose tolerance factor and chromodulin. The trophic effect of Cr is to enhance communication between insulin and its receptors located on the cell membrane of insulin-sensitive tissues by increasing membrane fluidity and rate of insulin internalisation. High carbohydrate intake, aging, stress, pregnancy, lactation, acute exercise, and obesity cause Cr depletion and increase demand. In addition to diabetes, Cr deficiency in laboratory animals is characterized by corneal opacities, decreased survival rate, decreased growth rate, and reduced longevity and reproductive efficiency that may be pertinent to livestock production. Livestock are supplemented with Cr to alleviate stress, enhance their immune and metabolic status, and improve performance and food quality. A reduction in adverse effects of stress and enhancement of metabolic status are consistent responses to Cr supplementation; improvements in performance and food quality parameters and enhancement of immune potency, however, are not.
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