The Nutritional Biochemistry of Chromium(III) - Survival-training.info

Use of chromium as an animal feed supplement 103of glucose and insulin as it relates to metabolism and growth is less complete thanin mammals. Basal glucose levels in chickens of 180–230 mg/dL would be relativelynormal [92, 93], and levels of several hundred could be found in smaller avians.Chickens that are raised for meat production are called broilers. They will be about40 grams at hatching and will be marketed at a weight of 2.4 kg at about 6 weeks ofage in the United States. During this period of growth, mortality will be about 4–5%of the flock depending on a variety of factors that may be related to diet, crowding,disease pressure, environmental stress (heat or cold), etc. Chickens that are raised foregg production are called laying hens or layers. They will begin laying eggs at about19–20 weeks of age and will generally lay for a minimum of 13–14 months. The averagelaying percentage (number of eggs per day/number of layers in the group) will start outlow and increase to 93–94%, averaging 82–84% over the productive life of the hen.Chromium for broilers (meat birds)Early studies with supplemental inorganic Cr +3 (CrCl 3· 6H 2 O) at levels of 20 ppmto young turkey poults demonstrated some improvement in growth rate and feed efficiency[94, 95]. Ward et al. reported a tendency for 200 ppb organic Cr (from CrPic)to increase carcass lean percentage and decrease fat percentage in young 3-week-oldbroiler chicks [96]. A study from Brazil where CrYst was supplemented from day 28post-hatching through slaughter at day 47 did demonstrate (P < 0.05) a reduction in fatpercentage of breast meat when the birds were supplemented with 400 ppb Cr from CrYst[97]; additionally, a 6-point improvement in feed efficiency (2.14 vs 2.20; P < 0.05) wasobserved with the supplementation. While this effect is encouraging, another study in thesame paper reported no effect of 300 or 600 ppb from CrYst on growth or feed efficiencywhen it was supplemented only during the first 21 days of life. As in the discussion ofthe effects in pigs, it should be noted that effects on carcass composition are cumulativeeffects; therefore, the length of feeding and relative age at slaughter are important factorsrelative to conclusions about the ability of a Cr form to effect carcass responses. Athird study that evaluated feeding during both the first and the second 3 weeks showedminor improvements in both the periods. The last study also demonstrated reductionsin mortality in the groups supplemented with Cr. Both the reduction in mortality andthe feed efficiency response have potentially large impacts on profitability. Studies fromthe Czech Republic have reported improvements in growth rate and feed efficiency ofturkeys supplemented with 400 or 2000 ppb of CrPic or chromium nicotinate for 88 days[98]. There were no differences between level or form of Cr. All supplemented birdshad lower fat content in breast meat.Lien et al. utilized broilers to evaluate the effects of 0, 800, 1600, and 3200 ppb Crfrom CrPic on growth and carcass responses [99]. Supplementation of 800 ppb had littleeffect, but 1600 ppb Cr increased growth rate with 3200 ppb supplementation having anintermediate effect. Both of the two upper levels did not affect feed efficiency as growtheffects were primarily through increases in voluntary feed intake. The two highest levelsof Cr increased liver fat percentage and decreased abdominal fat percentage. With regardto serum lipid responses, increasing levels of Cr resulted in numerical reductions in serumtriglycerides and cholesterol and significant reductions in NEFA; a greater percentage ofthe lipoproteins existed as HDL (compared to LDL and VLDL) with increasing levelsof Cr, but there was no difference in the proportion of total cholesterol bound to HDL.