Role of trace elements in animals : a review

Trace elements, though required in minute quantities (less than 100 mg/kg dry matter), are essential for maintaining health and immunity. They are involved in growth, production and reproduction. Trace elements act as cofactors of enzymes which are important to the immunity of animal. Superoxide dismutase , glutathione reductase, glutathione peroxidase, thioredoxin reductase, ceruloplasmin and catalase are important enzymes that have trace elements as cofactors. These enzymes act as antioxidants and prevent oxidative stress by neutralizing oxidants produced under different stresses. Besides, trace elements contribute to general health of animal thereby enhancing disease resistance. Trace elements are important for proper functioning of a number of enzymes and proteins which are involved in many physiological, biochemical and metabolic processes that contribute to growth and production. Overall, trace elements improve immune competence and productive performance.


Introduction
mechanisms and playing a vital role in many physiobiochemical processes like protein, enzyme and Trace elements are required in small amounts, hormone synthesis [20,21] or involving in oxidationusually less than 100 mg/kg dry matter [1,2] and are reduction reactions and immune functions [22].Trace present in very minute quantities in animal serum [3], elements are important for functioning of a number of usually less than 2 ppm.The seven main trace elements enzymes and proteins which are essential for a large include copper, iron, zinc, cobalt, iodine, manganese number of digestive, physiological and biosynthetic and selenium [4].Among these, iron (1.0-2.0 ppm) is processes within the body [23].Thus, they play a vital most abundant in serum followed by zinc (0.8-1.2 role in growth, production and reproduction [7,11].ppm) [4,5] and copper (0.57-1.0).On the other hand, cobalt (1-3 µg/dl), iodine (2.4-14 µg/100ml), manganese Health and immunity (18-19 µg/dl) and selenium (50-220 ng/L) are present Trace elements are essential for health and in least amounts [4,5].These are usually supplied via immunity [24].They are important for functioning of dietary intake of feeds and fodders [1].Though various components of the immune system [5].Their required in minute amounts, they are highly essential deficiency reduces disease resistance and increases the for health and immunity [5,6] mentation improves neutrophil's phagocytic capacity Trace elements also contribute to health and well being [26] and low copper status results in reduced neutrophil of animal through maintaining proper homeostatic phagocytic capacity [27].Selenium supplementation decreased somatic cell count (SCC).important for reproductive performance in livestock disease.In dairy cattle, plasma iron and zinc concen- [53] because their supplementation improves trations are decreased during the acute phase response reproduction [54].Studies show that the ovarian to immunological challenges [31], whereas plasma activity of ruminants is influenced by mineral deficiency copper concentration may increase [32].During [11].They are also involved in synthesis of hormones mastitis, increased secretion of lactoferrin in milk, a that are important for reproduction.Their deficiency binding protein, occurs which decreases the amount of affects both steroid [11] and thyroid [55] hormone available iron for Gram-negative bacterial growth [33]. production.

Trace elements contribute to general health by building
Copper and zinc play an important role in body defense mechanisms and improving metabolism regulating progesterone production by luteal cells via and hence their deficiency can predispose to diseases.
involvement of superoxide dismutase [56].Copper is Zinc is an essential trace element involved in the also involved in steroidogenic enzymes cytochrome catalytic, structural and regulatory processes of P , 17α-hydroxylase and cytochrome P side-chain keratinisation and in general protein metabolism [34].
450 450 cleavage and lysyl oxidase [57].Zinc is involved in the Consequently, teat canal keratin production is reorganization of ovarian follicles which are the source dependent on zinc status [34].Zinc is important for of progesterone.This occurs through the involvement immune function [21].There are increased risks of of metalloproteinase-2 (MMP-2) enzyme, which is a metritis, mastitis, locomotion problems or diarrhoea in member of zinc endopeptidase family [58].Zinc is also calves when zinc or copper levels are either marginal or involved in the secretion and function of male hormone deficient [35].
testosterone through the enzymes that control the Feeding organic zinc may have enhanced arachidonic acid cascade [59,60].Zinc is essential for resistance to mastitis causing pathogens because of thyroid hormone secretion and function.Thus, zinc improved skin integrity and keratin lining of the teat plays an essential role in sexual development and canal.Zinc plays role in maintaining structural spermatogenesis.Involvement of manganese in the integrity and health of the hoof and udder [13,36].Like synthesis and production of oestrogen and progesterone zinc, both copper and manganese are important for may be due to the fact that it acts as a cofactor in the keratin formation [13].This provides udder immunity.
synthesis of cholesterol, a precursor for steroids, Production including estrogen and progesterone [39].Iron also Trace elements improve growth [7,8] These play important roles in insulin, and growth hormone).Effect of trace elements oxidative stress [12,19].Selenium is an essential part on growth and milk production has been widely studied of a family of enzymes called glutathione peroxidases [9,34,38-46].Role of copper in growth is reported by (GSH-Px) and thioredoxin reductases [15] which are Hesari et al. [8], that of iron by Mohri et al. [47], manganese important for neutralizing free radicals or oxidants.by Hansen et al. [48], cobalt by Nagabhushana et al.Zinc and manganese, in addition to copper, are also [49] and zinc by Fagari-Nobijari et al [50].integral parts of SOD [13,17].All these neutralize free radicals like peroxides, super oxides or hydroxyl ions.It is important to note that the concentration of Trace elements are essential for reproduction trace elements change under different infections or [51].Earlier Manspeaker et al. [52] reported the inflammations.These ion changes reflect changes in importance of trace minerals in reproduction in cattle.cation binding of plasma proteins, and more Rabiee et al. [38] reported higher conception rates with importantly, alterations in cellular uptake mechanisms organic trace elements in cattle.Trace minerals are [5].These ionic changes help in preventing infection or Nutrient requirements of beef cattle.7 Rev. Industry.Proc Alltech's 14 Annual Symp.pp469-483.Ed.National Academic Press, Washington, DC. 24.Terpiłowska, S. and Siwicki, A.K. (2011) The role of selected th microelements: selenium, zinc, chromium and iron in 3. Suttle, N.F.(2010) Mineral Nutrition of Livestock, 4 immune system.Centr.Eur.J. Immunol.36 (4): 303-307.Edition.CABI Publishing, USA.25.Arthington, J.D. and Havenga, L.J. (2012) Effect of 4. Radostits, O.M., Gay, C.C., Blood, D.C. and Hinchliff, F.W. injectable trace minerals on the humoral immune response to (2007) Veterinary Medicine.A text book for the diseases of th multivalent vaccine administration in beef calves.J. Anim.cattle , sheep, pigs, goats and horses, 10 Ed.Bailliere Sci.90(6): 1966-71.Tindall, London.