Chapter 16

Chromium and Newly Discovered

Trace Elements

Chromium

--Cr is abundant in the earth's crust

--Cr occurs in the oxidation states of O, 2⁺, 3⁺ and 6⁺, most stable and biological effective in the trivalent state

--Most Cr ore used in production of stainless steel

--Because of poor absorption, used as a food passage marker

--Absorption estimated to be 0.5 to 2-3%

--Meats and whole grain products are best sources, while fruits, vegetables and milk very low

--Better sensitivity now for analyzing Cr, many earlier reports are unreliable

Essentiality

--1957, Schwarz and Mertz reported that a compound termed glucose tolerance factor (GTF) restored improved glucose tolerance to rats

--1959, Cr was identified as the critical substance that potentiated insulin action

--Cr yeast improved glucose tolerance in pigs by decreasing hepatic extraction of insulin (2000)

--Hexavalent Cr compounds are inactive

--Cr as GTF is absorbed better, has a different tissue distribution and is available to the fetus

--GTF is 50 times more active than inorganic Cr (III)

--GTF might qualify as a vitamin since it contains Cr, organic components (nicotinic acid, glycine, glutamic acid and cysteine) and is more biologically available than inorganic sources of Cr alone. This is comparable to the relationship of Co and vitamin B₁₂

--Cr is a potentiator of insulin action (Offenbacher et al., 1997)

--Cr may form a complex between insulin and insulin receptors that facilitates the insulin-tissue interaction

--Suboptimal Cr for humans has led to detrimental changes in glucose, insulin and glucagon

--Most popular supplemental form is Cr picolinate (Anderson, 2002)

--New Cr product being developed, Cr-histidine more reading absorbed than Cr picolinate (Anderson, 2002)

--For nonruminants supplemental Cr (chromium picolinate) may ↑ carcass lean and ↓ carcass fat

--100-800 ppb Cr reduced back fat and increased longissimus muscle area and percent muscling in pigs (Page et al., 1993; Min et al., 1997)

--In broilers, dietary Cr (⁺3) improved growth rate, F.E. and increased meat yield and carcass quality (Gürsoy, 2000)

--In humans and experimental animals, some studies have shown ↓ serum cholesterol and ↑ HDL cholesterol

--White leghorn hens receiving 800 ppb Cr (picolinate) ↓ serum and egg yolk cholesterol levels (Lien et al., 1996)

--A combination of Cr and Vitamin E improved egg production and F.E. for cold stressed layers (Dawe’s Lab, 2003)

--Cr improved reproductive performance in swine, large litters and birth weight (Lindermann et al., 1995)

--Immunity improved in dairy cattle, lymphocytes proliferated in response to a mitogen (Burton et al., 1993; 1996)

--Cr may alleviate effects of stress on shipped cattle, stressed calves had reduced morbidity following shipping (Mowat et al., 1993)

--For poultry, Cr supplementation was more critical under stressful conditions (Gürsoy, 2000), in poorly managed farms, chickens are likely to face greater environmental and nutritional stress

--Beneficial effects of Cr supplementation in malnourished children (Mertz, 1974), immediately restoring glucose tolerance

--Cr had beneficial effects for women with gestational diabetes (Anderson, 1998)

--Cr may be efficacious in treating type II diabetes (Hellerstein, 1998)

--Cr suggested for use in control of weight loss and body composition, perhaps if Cr status was low

--For horses results indicate that Cr tripicolinate supplemented yearlings ↑ rate which glucose is metabolized and may lower plasma glucose concentration (Ott and Kivipelto, 1999)

--Many Cr supplementation studies for livestock have had no positive results

Toxicity

--Trivalent Cr is poorly absorbed, so very high levels needed for toxicity

--Hexavalent Cr is much more toxic

--For trivalent Cr, cats tolerate 100 mg/d and rats showed no adverse effect from 100 mg/kg

--Chromic oxide (Cr₂O₃) is a fecal marker with levels as high as 3,000 ppm having no effects

--For humans with industrial exposure, symptoms were allergic dermatitis and skin ulcers, probably from airborne hexavalent Cr

--Chronic exposure to chromate dust ↑ incidence of lung cancer, growth depression, liver and kidney damage

--Dermatitis may be related to Cr in detergents and bleaches

--In animals, dermatitis, irritation of respiratory passages, ulceration and lung cancer

More Recently Discovered Elements

--The exact number of essential trace elements is not known

--The elements B, Li, Ni, Si, Sn, Br, V and Rb are relatively recently suggested as essential or of significance

--Apparent beneficial intake (ABI) is suggested terminology as essentiality and requirements have not been established for many species

Boron

Essentiality

--Known to be essential for higher plants since 1920s, more recent studies suggest boron is essential for animals

--Boron deficiency has been reported in rats, chickens and humans

--Boron deprivation affects function or composition of several body systems, including the skeleton, kidney and brain

--Addition of 5 ppm boron to a corn-SBM diet increased body weight of male but not female broilers (Rossi et al., 1993), tibia weight and breaking load were also increased

--B supplementation ↑ Ca and Mg retention in lambs

--Signs of B deficiency may be related to level of vitamin D and Mg

--B deprivation (0.3-0.4 ppm) depressed growth, hematocrit, hemoglobin and kidney weight in the rat

--B may regulate parathyroid function and indirectly influences metabolism of Ca, P, Mg and vitamin D

--B has been shown to be needed by the para-thyroid and has been shown to prevent loss of Ca and bone demineralization in post-menopausal women (Nielsen et al., 1988)

--Newnham (1980s) suggested that rheumatoid arthritis can be prevented and cured with B in both humans and animals

--Long-term effects of B supplementation had beneficial effects upon reproduction and bone characteristics in gilts (Armstrong et al., 2002)

--Dietary B supplementation increased cytokines in pigs following a stress, indicating an immune role (Armstrong and Spears, 2003)

--Physiological amounts of B may help reduce the amount of insulin required to maintain blood glucose (Bakken and Hunt, 2003)

Toxicity

--A low order of toxicity, 150 ppm for cattle

--Toxicity in cattle, inflammation and edema in legs, ↓ F.I. ↓ growth, ↓ hemoglobin

--High B detrimental to riboflavin, inducing in poultry "curled-toe" paralysis

--High B ↓ F absorption

Lithium

--Leafy vegetables, roots and fruits are good sources

--Li used in medicine to treat recurrent manic-depressive psychosis

--Goats deficient in Li gained 26% less, needed more inseminations to become pregnant, increased abortions, ↓ milk production, and ↓ reproductive performance

--Li deficient rats, ↓ reproductive performance

--Toxicity effect (humans), depressed thyroid function

Nickel

--Recognized essential for swine, the chick, rat, and ruminants

--Plant foods are higher in Ni than food of animal origin

--Swine and goats have ↓ body weight, ↑ mortality rate

--Ni is a component of urease, found as enzyme also in aerobic hydrogen and anaerobic bacteria

--Ni deficient goats fed < 10 ppb in diet had ↑ abortion rates, ↓ viability of female goats and offspring, ↓ milk production, skin and skeletal lesions (Anke et al., 1990)

--About 20-30% of pigs on low diet had scaly and crusty skin similar to parakeratosis (similar to Zn deficiency), also ↓ Zn tissue levels suggest Ni deficiency affects Zn metabolism.

--Ni at 40-60 ppm may be toxic, high Ni reduced Fe and Mn in plants

--Ni toxicity in a number of species, ↓ F.I., ↓ growth

Silicon

--Most abundant element on earth next to oxygen, the most abundent in earth's crust

--High content of Si in soils, plants, and atmospheric dust results in high intakes by animals and man

--Supplemental Si increased plasma and milk Si concentrations in horses (Lang et al., 2001)

--Essential for growth and skeletal development in rats and chicks (requirement, 50-500 ppm) (Carlisle, 1974)

--Si deficiency results in altered composition and strength of bones

--Skull abnormalities, with reduced collagen content produced in Si-deficient chicks

--Si required for prolyl hydroxylase, activity of the enzyme, a measure of rate of collagen biosynthesis

--Si is essentially non-toxic for monogastrics, however ruminants may develop siliceous renal calculi with toxicity

--Si toxicity in miners, develop a chronic lung disease

--Particles of Si and asbestos stimulate a severe fibrogenic reaction in lungs and elsewhere

--Silica urolithiasis serious problem in grazing wethers in Australia and grazing steers in U.S-Canada

--This is in contrast to urolithiasis in humans where oxalates play more of a role

--Si for grazing sheep is a major cause of teeth wear

Tin

--Organic Sn is biologically more available

--With Sn deficiency reports of growth effects in rats, teeth pigmentation effects

--Sn thought to be needed for tertiary structure of proteins and an oxidation - reduction catalyst

--However, now lack of evidence of essentiality as experiments with rats were riboflavin-deficient (Nielsen, 1986)

--Oxidation-reduction potential of Sn²⁺ Sn⁴⁺ is 0.13 V, about the same for flavin enzymes

--So can not consider Sn an essential element at this time

--Stannous chloride most toxic form of Sn

--With toxicity, growth depression, ↓ hematopoeises and altered Ca metabolism

--Sn can interfere with porphyrin biosynthesis and enhance heme breakdown

Vanadium

--Distributed widely in nature

--Can exist in oxidation states from 1^- to 5⁺

--Whole grains, seafood, meats and dairy products good sources (5-30 ppb)

--V is essential for the chick and rat

--V deficiency, ↓ body and feather growth, impaired reproduction, ↓ survival of young, ↓ red blood cells

--V requirement between 0.05 and 0.5 ppm

--Deficiency in goats, ↑ abortion, ↓ milk and ↓ life expectancy, more than 50% of kids died between 7-91 days of life (Anke et al., 1984)

--V is relatively toxic (~10-30 ppm of diet)

--V toxicity results in diarrhea, emaciation and prostration in calves

--With toxicity, dry matter digestibility ↓ in rumen

--V toxicosis of consequence, depending on its content in phosphate rock used in supplementation (Ammerman et al., 1977)

--As much as 1400 ppm V in phosphate adversely affects growth in chicks

--Potentially toxic, V may be encountered by grazing animals through soil ingestion

--Toxicity to humans from exposure to airborne, V- bearing dusts. This causes cough and irritation of the respiratory passages, green coloration of the tongue, dermatitis, dizziness and cardiac arrhythmias

Bromine

--Br deficiency in goats resulted in growth, low conception rates, ↓ milk fat production, ↓ hemoglobin and shortened life expectancy (Anke et al., 1990)

Rubidium

--Female goats fed < 280µ g/kg Rb (vs. 10 mg/kg), abortion, lower birth weight, and ↑ mortality among kids (Anke et al., 1997)

Other Elements

Other elements may be essential: antimony, barium, germanium, cesium, silver, strontium, titanium, zirconium, beryllium, bismuth, gallium, gold, neodymium, scandium, tellurium, thallium, and tungsten

-Other elements much more likely to be toxic than deficient