CHROMIUM, THE NUTRIENT OF TOMORROW FOR ANIMALS
Dept. of Nutrition & Clinical Nutrition, Faculty of Veterinary Medicine,
Cairo University, Giza 12211 Egypt.
It is well recognized that chromium is an essential trace element in human and laboratory animal nutrition. Chromium functions primarily by potentiating the action of insulin. Schwarz and Mertz in 1959 were the first to identify chromium as the active constituent of the glucose tolerance factor (GTF). Chromium may have several biological functions, including activating certain enzymes and maintaining structural integrity of nucleic acids, but its main role is as the key component of the GTF which enhances the action of insulin. Chromium occurs primarily in the trivalent and hexavalent forms; the form in higher organisms is trivalent. This mineral occurs throughout the body with highest concentrations in the liver, kidney, spleen and bone. Insulin which is the master hormone of metabolism; not only helps controls blood sugar levels, but also helps regulate the metabolism of fats, proteins, and energy. Insulin also exerts profound effects on many other body tissues. It controls how the body's cells absorb, use and store nutrients and energy. Besides regulating the cellular absorption and utilization of glucose, amino acids and fatty acids, insulin also activates and inactivates enzymes and directly affects certain genetic processes including protein synthesis. Chromium affects body composition in different species. Recent research with humans and mice has shown that various stresses such as low protein diets, infection, strenuous exercise and trauma increase the urinary excretion of chromium. Chromium supplementation in mouse diets has been effective in reducing stress-induced losses of zinc, iron, copper and manganese in urine. Chromium could well be the next trace element routinely added to salt. Recent research has shown that chromium is most beneficial in high-stress periods which will often impair the immune system and make animals more susceptible to invading pathogens. It is likely that this level of stress increased urinary chromium excretion and depleted body chromium stores. Stress also causes increased glucose mobilization which increases mobilization of chromium from body stores. The exact mechanism by which chromium enhances the immune system is not known. However, one of the consistent results of the studies was that chromium reduced serum cortisol levels. Glucocorticods, which include cortisol, are known to suppress the immune system.
Two general forms of chromium have been used in supplementation trials, the inorganic form and organic forms that seem to have greater availability. However, because small concentrations are required, inorganic chromium may be an economical source in many diets. Plant products contain a low content of chromium, implying that animals and poultry may have a deficiency of chromium because their diets consist either of all or a large proportion of plant ingredients.
In conclusion there is a growing body of evidence which suggest that chromium may be an essential trace element for livestock and poultry. The nutritional requirement for chromium may vary with different specie and physiological state within a species.
Keywords: chromium, Immunity, performance, poultry, calves, blood chemistry profile.
Minerals play a substantial role in nutrition. Mineral nutrition is a complex part of feeding management. Deficiencies and toxicities can occur through inattention to feeding management or simple availability. Typical mineral-related problems stem from providing inadequate amounts or minerals in incorrect proportions. The role of trivalent chromium as an essential trace element in human and laboratory animal nutrition is well documented (Anderson, 1987; Offenbacher and Pi-Sunyer, 1988; National Research Council (NRC) of human, 1989; Lien et al., 1993). Although an appropriate recommendation on the chromium requirement of poultry and animals has been not made (NRC, 1994), there is an increasing body of evidence which suggests that chromium may also be an essential trace element for poultry and animals.
Chromium is involved in carbohydrate metabolism and recognized as glucose tolerance factor (GTF) (Schwarz and Mertz, 1959, Rosebrough and Steele, 1981). It functions primarily by potentiating the action of insulin which is a master hormone of metabolism; it not only helps controls blood sugar levels, but also helps regulate the metabolism of fats, proteins, and energy (Steele and Rosebrough, 1981; Okada et al., 1984; Ohba et al., 1986; Press et al., 1990; McCarty, 1991 and Page, 1991). It was reported early that chromium might have a role in nucleic acid metabolism because of a significant increase in stimulation of amino acids incorporation into liver protein in vitro (Weser and Koolman 1969). Inconsistent responses of circulating lipid and lipoprotein concentrations due to chromium supplementation were reported (Lukaski, 1999). Chromium also is involved in modulating the immune response in animals (Chang and Mowat 1992; Moonsie-Shageer and Mowat, 1993; Chang et al., 1994, and Cerulli et al., 1998).
Two general forms of chromium have been used in supplementation trials, the inorganic form (CrCl3.6H20) and organic forms that seem to have greater availability (Lukaski, 1999). However, because small concentrations are required, chromium chloride and not organic forms may be an economical source in many diets. Plant products contain a low content of chromium, implying that poultry and animals may have a deficiency of chromium because their diets consist either of all or a large proportion of plant ingredients (Schroeder, 1971 and Gibson, 1989).
Chromium is an essential trace mineral nutrient (Stoecker, 1996). Recently called the nutrient of tomorrow. Like other essential trace minerals, chromium plays a critical role in maintaining normal health and well being (Shils and Young, 1988). The role of chromium as an essential trace element in human and laboratory animal nutrition is well-recognized (Anderson, 1987; Offenbacher and Pi-Sunyer, 1988). It is surprising that all of the recent publications of National Research Council who publish the nutrient requirements of farm animals, poultry and other animals did not include chromium requirements for farm animals and poultry due to lack of essential information about it. Although the publications for human and laboratory animals include some informations regarding chromium. This was the case in the past with other trace elements such as cobalt, zinc and copper.
Biological Functions:
Chromium functions primarily by potentiating the action of insulin (Davis and Vincent,1997). Schwarz and Mertz in 1959 were the first to identify chromium as the active constituent of the glucose tolerance factor (GTF). The exact structure of GTF is unknown, it is thought to be a nicotinic acid-trivalent chromium-nicotinic acid axis with ligands of glutamic acid, glycine and cysteine (Mertz et al., 1974). Chromium may have several biological functions, including activating certain enzymes and maintaining structural integrity of nucleic acids, but its main role is as the key component of the GTF, which enhances the action of insulin.
Chromium and Poultry:
Rosebrough and Steele (1981) reported that adding 20 ppm chromium from CrCl3 increased (P<.05) weight gains of turkey poults fed diets that were protein deficient. Turkeys fed the supplemental chromium had higher liver glycogen levels as a result of increasing the activity of the enzyme glycogen synthetase. In addition, chromium increased glucose transport by increasing insulin activity. In 2001, The author and Afifi reported an enhancing effect of inorganic chromium supplementation to broiler. There were a highly significant (P<0.01) improvement in all chromium supplemented groups (20 and 40 ppm) throughout the experimental period with non-significant differences between 20 and 40 ppm chromium supplementation. Chromium supplementation (20 and 40 ppm) improved weight gain, reduced feed intake and improved feed conversion. The obtained results nearly coincided with those obtained with Steele and Rosebrough, (1979) and Rosebrough and Steele, (1981) in turkey poults as well as Lien et al. (1999) in broilers. However. Cupo and Donaldson, (1987) reported that supplemental chromium had no effect on body weights of chicks. Similar results were reported by Kim et al. (1996). The enhancing effect of chromium supplementation could be attributed to its involvement in stimulating the biological activity of insulin by increasing the insulin-sensitive cell receptors or binding activity (Mertz et al., 1974; Anderson et al., 1987, 1991; McCarty, 1991; Morris et al., 1993; Ward et al., 1994 as well as Lien et al., 1999). Insulin can also stimulate anabolism and inhibit catabolism (Lien et al., 1999). In addition, chromium is involved in protein metabolism (Lukaski, 1999). Chromium may have a role in nucleic acid metabolism because of a significant increase in stimulation of amino acid incorporation into liver protein in vitro (Weser and Koolman 1969 and Lukaski, 1999). Moreover, Okada et al., (1983) reported an evidence of a direct interaction of chromium with DNA templates that resulted in a significant stimulation of RNA synthesis in vitro (RNA is responsible for protein synthesis during growth and regeneration) and subsequently identified a unique protein containing 5-6 atoms of chromium to which the anabolic function was ascribed (Okada and Tsukada 1985, Okada et al., 1989 and Lukaski, 1999).
Chromium and Human, Mice and Rats:
Recent research with humans and mice has shown that various stress factors such as high glucose intakes, low protein diets, infection, strenuous exercise and trauma increase the urinary excretion of chromium. Chromium supplementation in mouse diets has been effective in reducing stress-induced losses of zinc, iron, copper and manganese in urine. Similar responses have been observed with protein-deficient rats (Mertz and Roginski, 1963). When additional stress was applied through controlled exercise or blood loss, rats fed chromium deficient diets had poorer performance and survival. Differences in performance were not due to increased water content, but reflected changes in the amount of carcass protein. Research with humans and mice (Anderson, 1988) has shown that stress increases the urinary excretion of chromium.
Chromium and Calves and Dairy Cows:
Chang and Mowat, (1992) showed that adding 0.4 ppm chromium from high-chromium yeast improved weight gains and feed efficiency in stressed feeder calves. Moreover, supplemental chromium also decreased serum cortisol and improved immune response in stressed calves (Mowat and Chang. 1992). In a Canadian study, chelated chromium reduced morbidity to less than one-third of that in the control group. This might be helpful in lowering levels of antibiotics that would be required for the treatment of sick feeder cattle. Chromium is most beneficial in high-stress periods. Shipping stress, for example, will often impair the immune system and make animals more susceptible to invading pathogens. Chang and Mowat (1992) evaluated the effects of supplemental chromium, from high-chromium yeast, on the performance and health of stressed calves with or without long-acting oxytetracycline. During the first 28 days after shipping, feeding 0.4 ppm chromium increased averaged daily gains (1.34 vs. 1.74 lb/day) and gains per unit of dry matter intake (0.123 vs. 0.156) in calves not receiving oxytetracycline. However, chromium supplementation had no effect on performance of calves receiving the antibiotic. It is likely that this stress increased urinary chromium excretion and depleted body chromium stores. Stress often causes increased glucose mobilization which increases mobilization of chromium from body stores.
Chromium and Immunity:
Peak antibody titers to human red blood cells and immunoglobulin G1 concentrations were increased (P<.07) due to chromium supplementation. The effects of supplemental chromium on immune responses of dairy cows subjected to physical and metabolic stresses associated with late pregnancy, calving, and peak milk yield were determined. Chromium caused increased anti-ovalbumin response (P <.01) but did not affect the immune response to the red blood cells. The exact mechanism by which chromium enhances the immune system is not known. However, one of the consistent results of the studies was that chromium reduced serum cortisol levels. Glucocorticods, which include cortisol, are known to suppress the immune system.
In humans and mice research has shown that various stress factors such as high glucose intakes, low protein diets, infection, strenuous exercise and trauma increase the urinary excretion of chromium. Chromium supplementation in mouse diets has been effective in reducing stress-induced losses of zinc, iron, copper and manganese in urine. In one Canadian study, chelated chromium reduced morbidity to less than one-third of that in the control group. Research has shown that chromium is most beneficial in high-stress periods. Shipping stress, for example, will often impair the immune system and make animals more susceptible to invading pathogens. Monnsie-Shageer and Mowat (1993) fed 0, 0.2, 0.5, and 1 ppm supplemental chromium from high-chromium yeast, to 84 Charolais-crossed feeders stressed due to shipment. Chromium supplementation decreased morbidity (P <.05) and rectal temperature at day 2 and 5 after arrival. Peak antibody titers to human red blood cells and immunoglobulin G1 concentrations were increased (P <.07) due to chromium supplementation. The basal corn silage diet contained 0.16 ppm chromium. The effects of supplemental chromium on immune responses of dairy cows subjected to physical and metabolic stresses associated with late pregnancy, calving, and peak milk yield were determined. Chelated chromium (0.5 ppm) was fed beginning six weeks pre-partum and continued through 16 weeks postpartum. To measure humoral immune responses, all cows were immunized with ovalbumin and human red blood cells approximately two weeks before and two weeks after calving. Chromium caused increased anti-ovalbumin response (P <.01) but did not affect the immune response to the red blood cells.
The effect of dietary chromium on Lymphocyte Blastogenesis in chickens as judged with stimulation index using MTT assay was studied by the author and Afifi (2001). Results indicated that 20 ppm chromium supplementation significantly (P<0.05) increased the stimulation index 21, 28 and 35 days from the beginning of the study while 40 ppm chromium supplementation significantly (P<0.05) increased the stimulation index earlier at 14 days. Chromium may enhance some aspects of cell-mediated immunity (Lukaski, 1999). Chromium supplementation increased proliferation of peripheral blood lymphocytes in terms of increased blastogenic activity of peripheral blood lymphocytes incubated with a mitogen (Chang et al., 1994, and Cerulli et al., 1998). We also studied the effect of dietary chromium on haemagglutinin antibody titre in chickens immunized with sheep RBCs. Results indicated that in comparison to the control non-supplemented group, chromium supplementation at a level of 20 ppm significantly (P<0.05) increased the haemagglutinin antibody titre 21 and 28 days post immunization with SRBCs. On the other side, chromium supplementation at a level of 40 ppm significantly (P<0.05) increased the haemagglutinin antibody titre at 2 weeks earlier (7 and 14 days post immunization with SRBCs) compared to 20 ppm chromium supplemented group. Moonsie-Shageer and Mowat, (1993) pointed out that antibody titers of stressed feeder calves (to human RBCs) fed chromium were higher during the primary response to the challenge. Animals and birds mounted a response to a fairly complex antigen (SRBCs) and, therefore, might be expected to mount a nearly similar response to both bacterial and viral challenge. Chromium may improve the effectiveness of vaccination by improving the immune function through reduced cortisol or through other mediators released by the cells of the immune system. Additional evidence on the enhancing effect of chromium on humoral immunity was reported by Chang and Mowat (1992) who reported an improvement of IgM and total immunoglobulin levels and by Moonsie-Shageer and Mowat, (1993) in terms of increased IgG1 by supplemental chromium.
Chromium and Serum Chemistry:
The findings of the author and Afifi (2001) indicated that chromium supplementation had no significant effect on total protein or albumin. Unlike the findings of Lien et al. (1999) who reported a significant reduction in serum glucose as a result of chromium supplementation, our results indicated that chromium supplementation had no significant effect on serum glucose. These results coincided with those obtained in turkey poults (Rosebrough and Steele, 1981). In vitro studies on the uptake and oxidation of glucose by liver slices from chicks revealed that chromium increased the rate of glucose utilization 16% over control (Cupo and Donaldson, 1987).
Chromium supplementation results in equivocal responses in circulating lipids and lipoprotein concentrations (Lukaski 1999). The dietary supplementation of two levels (20 and 40 ppm) of inorganic chromium significantly (P< 0.05) reduced serum total cholesterol, serum triglycerides as well as LDL cholesterol. However, statistical analysis revealed non-significant differences between 20 and 40 ppm chromium supplementation Mohamed and Afifi (2001). On the other side, chromium supplementation significantly (P<0.05) increased the serum HDL cholesterol. Similar data were reported by Lien et al., (1999) in broiler and by (Lukaski 1999) in human subjects. A previous study indicated that insulin with its stimulated biological activity due to dietary chromium, can increase the lipoprotein lipase activity and eventually decrease the contents of triglycerides rich lipoproteins (Garfinkel et al., 1976 and Howard et al., 1993). It also can increase liver LDL receptors, thereby reducing the LDL content and concomitantly the HDL proportion is increased (Brindley and Salter, 1991 and Lien et al., 1999). Moreover, we found that chromium dietary supplementation had no effect on serum alkaline phosphatase, serum ALT, serum AST or serum uric acid indicating that inorganic dietary chromium had no deleterious effect on the liver or kidney functions.
In summary, there is a growing body of evidence which suggest that chromium may be an essential trace element for livestock and poultry. We expect future publications of NRC to include chromium requirements for different classes of farm animals and poultry as well.
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