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

Use of chromium as an animal feed supplement 91In summary, in spite of a few positive observations, there do not appear to be anygeneralized improvements in immunocompetence in young pigs with the supplementationof Cr, even though this is a period of time when the immune system of the pigis compromised. Further, while there are two studies that report improved growth andimproved nutrient digestibility with supplementation of 200 ppb Cr from CrPic [29, 30],there does not appear to be any generalized improvement in growth performance duringthis period with Cr supplementation. It should be noted that young pigs such as used inthese studies would have been only 5–20 kg BW (compared to a mature body size of150–250 kg BW) and would not have experienced very much of the normal dilution ofbody Cr that occurs with age (as presented earlier) and thus may not be in particularneed of the nutrient.Chromium for growing pigsFollowing the nursery phase, pigs are generally moved into another building inwhich they are fed until they reach market weight. In the early part of the twentiethcentury, pigs were extremely fat because the fat had commercial value as it was usedto make nitroglycerin which had military uses [31]. Following World War II, this needfor fat ceased, and a consuming public was more interested in a leaner product. Thusthroughout the 1960s, 1970s, and 1980s, there was an intensive effort to change thebody type of the pig to be more lean through genetic selection and through dietarymodifications that would result in more lean (muscle) deposition and less fat deposition.In the current marketing structure, producers are rewarded for pigs with higher amountsof muscle and are discounted for pigs with high fat content. The interest in Cr supplementationduring this period in the life of the pig is primarily for its potential impact onmuscling, and secondarily for any potential improvement in feed efficiency (if a pig cangain the same amount of weight on less feed, there is an obvious reduction in cost for theproduction of that pig). Muscling in pigs is generally measured by the cross-sectionalarea of the longissimus muscle (a large muscle that lays perpendicular to the backboneand is processed into the “pork chop”), the fat depth at the 10th rib (this would equateto the amount of fat on the outside of the pork chop), or by the overall lean percentagein the carcass which is computed from the weight of the pig, the longissimus musclearea (LMA), and the 10th rib fat depth (TRF).Great enthusiasm for the potential of Cr to improve muscling was generated bythe initial reports of a series of trials with CrPic from the laboratory at Louisiana StateUniversity (LSU) [32]. Researchers reported increased LMA and decreased TRF ofcarcasses at market when Cr was fed to the growing pigs. In some of the trials the LMAincreased more than 20% and the TRF decreased more than 25%. Interestingly, in thethree trials reported, the magnitude of increase in LMA and decrease in TRF was greateras the starting weight of the pigs on test decreased from 37.8 kg in Trial 1 to 22.4 kg inTrial 3. This effect is not surprising because any benefit that Cr might have on carcassmeasurements would be cumulative, so that number of days of supplementation should berelated to the desired response. These researchers also established that supplementationof Cr as chromium chloride or of picolinic acid in the same quantity as that suppliedwhen 200 ppb Cr was supplied as the specific compound CrPic did not elicit any positivemuscling effects. The lack of effect of Cr as chromium chloride was consistent withprevious evaluations [33]. Studies at Virginia Polytechnic Institute and State University