Dietary chromium - forms and availabilities

The importance of nutrition in alleviating high stocking density stress in poultry

In recent decades, the number of birds reared per unit area has dramatically spiked to increase profitability in egg and meat production. However, nowadays, the increase in sensitivity to animal welfare and consumer demands brings along with it a raised interest in stocking density. Stocking density is defined either as the number of animals or body weight per unit area or as the area per animal. High stocking density, which is a stress factor, can be defined as an increase in the number of animals per unit area or a decrease in the area per animal. Stress caused by high stocking density negatively affects the bird’s physiology and performance as well as the quality of the product obtained. The ideal stocking density should be 9 laying hens, 35 kilogrammes for broilers, and 45 quails per square metre. Otherwise, one will observe stress indicators in birds reared in more than the recommended stocking density per unit area and, consequently, a decrease in bird growth, egg production, feed efficiency, and egg or meat quality. Apart from increasing the concentrations of amino acids such as lysine, methionine, tryptophan and arginine, minerals such as selenium and chromium, and vitamins such as C and E in the diet, the addition of additives such as probiotics, humates, phytophenol compounds, and propolis is also effective in reducing or eliminating these negative effects caused by high stocking density. As a result, regulations in the nutrition of animals are effective in reducing/preventing such negative effects, thus improving animal welfare and ensuring the maintenance of optimum yield.

Dietary chromium modulates glucose homeostasis and induces oxidative stress in Pacific white shrimp (Litopenaeus vannamei)

While chromium (Cr) has been recognized as an essential nutrient for all animals, and dietary supplementation can be beneficial, it can also be toxic. The present study aimed to investigate the contrasting effects of dietary chromium in Pacific white shrimp Litopenaeus vannamei. Five experimental diets were formulated to contain Cr at levels of 0.82 (Cr0.82, unsupplemented diet), 1.01 (Cr1.01), 1.22 (Cu1.22), 1.43 (Cr1.43) and 1.63 (Cr1.63) mg/kg and were fed to shrimp for 8 weeks. Highest weight gain was recorded in shrimp fed the diet containing 1.22 mg/kg Cr. Shrimp fed the diet containing the highest level of Cr (1.63 mg/kg) showed the lowest weight gain and clear signs of oxidative stress and apoptosis as evidenced by higher levels of H₂O₂, malondialdehyde and 8-hydroxydeoxyguanosine, and expression of caspase 2, 3, 5, and lower contents of total and oxidized glutathione, and expression of Cu/Zn sod, cat, gpx, mt, bcl2. Chromium supplementation promoted glycolysis and inhibited gluconeogenesis as shown by increased activities of hexokinase, phosphofructokinase and pyruvate kinase, and reduced activity of phosphoenolpyruvate carboxykinase in shrimp fed the diet containing 1.43 mg/kg Cr. Shrimp fed the diet with 1.63 mg/kg Cr had lowest contents of crustacean hyperglycemic hormone and insulin like peptide in hemolymph. Expression of genes involved in insulin signaling pathway and glycose metabolism including insr, irs1, pik3ca, pdpk1, akt, acc1, gys, glut1, pk, hk were up-regulated, and foxO1, gsk-3β, g6pc, pepck were down-regulated in shrimp fed the diets supplemented with Cr. This study demonstrated that optimum dietary supplementation of Cr had beneficial effects on glucose homeostasis and growth, whereas excess caused oxidative damage and impaired growth. The results contribute to our understanding of the biological functions of chromium in shrimp.

Effects of chromium supplementation from inorganic and organic sources on nutrient utilization, mineral metabolism and meat quality in broiler chickens exposed to natural heat stress

One hundred 1-day-old Ven Cobb chicks were used to study the effect of supplementation with 0-2 mg chromium (Cr) per kg diet from potassium chromate (T1), chromium chloride (T2) and chromium-yeast complex (T3). The control group (C) received no supplemental chromium. Each experimental group consisted of five replicates of five birds each and the supplementation was continued for 35 days. The weekly live-weight gain, food conversion ratio and the live-weight gain: food intake ratio were unaffected by the treatments. Metabolizability of the organic nutrients increased in the Cr supplemented groups compared with the C group and significantly higher values were observed in the T3 group indicating beneficial effects of Cr-yeast complex. Intake of the trace elements (copper, zinc, iron and manganese) fulfilled the requirements specified for broiler chickens. Retention of all these trace elements was higher (P < 0-001 for Cu, Zn and Fe, P <0-01 for Mn) in all the Cr supplemented groups compared with that in the C group. Furthermore, in the T3 group the retention of copper, zinc, iron and manganese was higher (P < 0001) than that in the T1 and T2 groups. Two birds were slaughtered from each replicate at the end of 21 and 35 days of feeding to observe Cr in the liver; this was higher (P < 0-01) after 35 days feeding only. Despite supplementation, liver Cr was lower (P < 0-01) in T1 T2 and T3 groups. Cr concentration in the plasma was higher (P < 0-05) in the T3 and T3 groups than that in the C group although its concentration did not change with the age of the birds. Higher (P < 0-01) plasma concentrations of copper were observed in the T1 T2 and T3 groups titan those in the C group. The differences between the Cr supplemented groups in this respect were not significant, however. Liver copper was higher (P < 0-001) in C while liver iron was the lowest (P < 0-05) in that group. The concentrations of copper, iron (P < 0-01) and zinc in the liver (P < 0-05) were higher after 35 than after 21 days while those of manganese were not affected by slaughter age. Protein accretion in the meat tended to be increased in the Cr supplemented groups while deposition of fat in the meat was lower but these differences were not significant (P > 0-05). Other meat quality parameters including sensory evaluation scores improved due to Cr supplementation and Cr-yeast complex was found to have exerted significantly greater effects on these parameters. It was concluded that the supplementation of 0-2mg Cr per kg food dry matter would improve the performance of broiler chickens in terms of metabolizability of organic nutrients, retention of trace elements and meat quality.

Effects of dietary organic chromium and vitamin C supplementation on performance, immune responses, blood metabolites, and stress status of laying hens subjected to high stocking density

The present study was carried out to investigate the effects of dietary supplementation of chromium-methionine (CrMet) and vitamin C (VC) on performance, immune response, and stress status of laying hens subjected to high stocking density. A total of 360 Hy-Line W-36 leghorn hens (at 26 wk old) were used in a 2×3×2 factorial arrangement that had 2 cage densities (5 and 7 hens per cage), 3 Cr levels (0, 500, and 1,000 ppb as CrMet), and 2 dietary VC levels (0 and 500 ppm as L-ascorbic acid). The trial lasted for 12 wk. The first 2 wk were for adaptation (26 to 28 wk of age), and the remaining 10 wk served as the main recording period. In addition to performance, immune response to Newcastle disease virus (NDV) was assessed at d 7 and 14 postvaccination. Also, the birds' stress status was evaluated by analyzing appropriate plasma metabolites. The results showed that hens in cages with higher stocking density had lower hen-day egg production, egg mass, and feed intake compared with those in normal density cages (P<0.05). Dietary CrMet supplementation caused significant increases in egg production and egg mass (P<0.01). There were significant Cr × VC interactions related to egg production and feed conversion efficiency (P<0.01); dietary CrMet supplementation was more effective in improving egg production and feed conversion ratio in VC-unsupplemented diets. Although plasma concentrations of triglycerides and high-density lipoproteins were not influenced by dietary treatments, supplemental CrMet decreased plasma cholesterol levels (P<0.05). Plasma insulin and glucose levels of hens kept at a density of 7 hens/cage were significantly higher than those of hens in normal cage density (P<0.01), and dietary CrMet supplementation decreased plasma concentrations of insulin (P<0.001) and glucose (P<0.01), with higher impacts in high stocking density-challenged hens. While high stocking density caused a marked increase in plasma corticosterone (P<0.01), both supplemental CrMet and VC decreased it to near normal levels. There were significant stocking density×Cr interactions related to plasma insulin and corticosterone concentrations (P<0.01); supplemental CrMet was more effective in lowering these hormones in high stocking density-challenged hens. The high stocking density challenge suppressed NDV antibody response (P<0.001), while dietary supplementation of CrMet improved antibody titers against NDV at d 14 post vaccination particularly in hens kept at a density of 7 hens/cage (P<0.01). From the present observations, it can be concluded that CrMet can improve laying performance largely because it alleviates harmful responses to stressful conditions.

Bioaccumulation and toxicology of chromium: implications for wildlife

The major source of exposure to Cr for wild birds and mammals is through ingestion with food. Chromium(VI) compounds are absorbed significantly more efficiently (2-10% of dose) from the GI tract than inorganic Cr(III) compounds (0.5-3%), due to the increased membrane permeability of the former. Transfer of Cr(VI) into mammalian fetuses has been documented at oral doses of 500 mg Cr/L in drinking water, and injected single doses of 5 mg Cr(VI)/kg BW in dams were teratogenic. Cr concentration data for mammalian and avian wildlife species and their potential food organisms are scarce. Worldwide, fewer than 50 species of free-living mammals and birds have been surveyed with regard to tissue Cr concentrations. Tissue concentrations in animals living in habitats remote from sources of Cr contamination range from approximately 0.1-15 micrograms/g DW depending on the species and tissue analyzed. In habitats experiencing Cr pollution, levels can be up to two orders of magnitude higher. Eisler (1986) suggested that tissue concentrations in wildlife > 4 micrograms/g DW be considered to indicate likely contamination by Cr. Bone tissue often accumulates higher concentrations than other tissues in animals chronically exposed to Cr. Measuring concentrations only in the liver and/or kidneys has been a common practice, yet these organs failed to show evidence of extant Cr contamination in some cases. It is recommended that analysis of the bone, liver, and kidneys be a minimum requirement for future Cr biomonitoring studies. Concentrations in fur or feathers can be extremely variable even among individuals within the same habitat. At best, concentrations in fur and feathers might be used to indicate relative levels of airborne Cr contamination. The toxicological significance of "elevated" Cr concentrations is largely unknown because toxicological data on free-living wildlife species are virtually nonexistent. Based on controlled dosing studies in which Cr compounds were administered orally to experimental animals, dietary Cr concentrations > or = 10 micrograms/g DW in food should be considered potentially harmful to the health and reproductive success of wildlife consumers. Certain species of fish and aquatic invertebrates are sensitive to Cr, showing reduced survival or growth at Cr(VI) concentrations > 10 micrograms/L. The elimination of these organisms from environments contaminated with Cr may have detrimental effects on wild birds and mammals that depend on such organisms for food.(ABSTRACT TRUNCATED AT 400 WORDS)

Oral bioavailability of chromium from a specific site

Analysis of soil from a specific site in New Jersey indicated a low level of sodium and chromium present as a calcium compound. Chromium was then administered orally to young, mature male rats at a level of 240 micrograms/kg for 14 days as chromium-contaminated soil, as CaCrO4, and as an equimolar mixture of the soil and calcium salts for 14 days. The rats were sacrificed 24 hr after the last dosing, and tissues were taken immediately for chromium analysis. Blood, muscle, and liver contained the highest levels of chromium in these animals, although kidney contained the highest concentration per gram of tissue. The total amount of chromium in the tissues was less than 2% of the administered chromium. In a study of the excretion of chromium, the animals were dosed orally for 8 days (with CaCrO4 or contaminated soil, each at the level of 240 mumole Cr/kg), and the chromium in feces and urine was determined on days 1, 2, 7, and 8. After cessation of dosing for 27 days, the same rats were dosed for 2 days at the same level, and chromium in urine and feces was determined for the 2 days. The animals administered the chromium in soil had higher levels of chromium in both urine and feces on all days compared to the group fed the CaCrO4. The total recovery of chromium in any of the 2-day periods was less than 50% of the chromium administered during that period.