Farming, Saturday, July 30, 1994 THE SELENIUM ISSUE The Problem Eight years ago, a report described high mortality rates in ducks near the Kesterson Reser voir in the*San Joaquin Valley of California. Excess selenium was apparently responsible for the deaths and poor reproductive rates among these water fowl. Where did the sele nium come from? It occurred naturally in the area, and was probably magnified from the runoff of irrigation water. The Blame Not long after the problem was discovered, environmental groups began pointing fingers at the lives tock industry. And so the Food and Drug Administration (FDA) looked into the issue, asking ques tions, such as; In what form does selenium come out of the animal? How does it move in the soil and effluent? Where does it go in water sheds?' Hearing unsatisfactory answers, the FDA decided that the livestock industry was feeding too much selenium. Most sensible individu als would struggle to make the connection between the dead ducks in an area of high selenium concentration and the minuscule amounts (.3 ppm supplemental) we feed to livestock. Yet the FDA announced September 13, 1993 that maximum supplemental sele nium in the livestock feeds would have to be reduced from .3 ppm to .1 ppm (diets for weanling pigs Pork Prose by Kenneth B. Kephart / Penn State Extension Swine Specialist would remain at .3 ppm, and .2 ppm for turkeys). The new regula tion went into effect immediately but will not be enforced for one year (September 13, 1994) to allow existing stocks of mineral mixes to be depleted. The Defense In the 10 months following the announcement of reduced sele nium, there has been a lot of ruck . us. Two highly respected organi zations, the American Feed Indus try Association (APIA) and the Council for Agricultural Science and Technology (CAST), have cri ticized the decision. Neither have a economic interest in whether we feed any selenium at all, but both organizations have rightfully pointed out that just as ducks die from too much selenium, so do livestock from not enough. In a recent CAST report, it was stated, “No scientific evidence or logic suggests that reducing sup plementary selenium from .3 ppm to .1 ppm in livestock diets will reduce selenium in regions of the U.S. in which an excess is pre sent” The report also pointed out that of the total amount of sele nium released in the U.S. annually from natural and commercial sour ces, the livestock industry contri butes less than .3 percent. Selenium occurs just about everywhere, but concentrations are low in the Northeast, the Pacif ic Northwest, and Southeast. It’s absolutely vital to pigs so they can make a selenium- The Nature Of Selenium containing enzyme called glu tathione peroxidase. This enzyme prevents the oxidation and destruc tion of cell membranes. In addi tion, selenium is important in anti body production and cell-mediated immune function. Selenium more or less works in conceit with vitamin E. Vitamin E prevents the formation of danger ous oxidizing agents in the body. Selenium plays a role in destroying the oxidizing agents if they do form. Like any essential element, sele nium is important But unlike other elements, there isn’t much room for error. A dietary level of only 5 ppm is toxic to the pig. Concentra tions of S-10 ppm can lead to anorexia, hair loss, fatty infiltra tion of the liver, degenerative changes in the liver, edema, and, under chronic conditions, spinal poliomalacia. A high level, even for a short time, may cause irrever sible damage. In 1974, the livestock industry was permitted to add .1 ppm of selenium. In 1982, the FDA increased the maximum supple mental level to .3 ppm for pigs up to 44 pounds. In 1987, the FDA increased the level to .3 ppm for all pigs. The important question debated now is how much is enough? The National Research Council (1988 swine edition) lists the followng requirements’ Selenium Requirements for Swine (NRC 1988) Weight Class, lb 2-11 11-22 22-44 44-110 110-242 gestation lactation Two things to keep in mind with this table. First, the amounts of selenium listed are total amounts that is, what occurs naturally in /-"s. Vi (6* ror ah \\ Your Concrete \r\ \C) W 3 * \.J) W ' SsS * r Walls And °~"KS Agriculture - Residential - Commercial • Buildings • Basement • Floors • Retaining Walls • Footer • SCS Approved Manure Storage Pits • All Types Of Flat Work /• // Virginia Style Heifer Barn With 8’ Deep, 180' Long, 12' Wide Slatted SCS Approved Concrete Manure Pit invest \n Concrete, Quality Work That Will Lest A Lifetime CALL FOR FREE ESTIMATES AND SEE HOW AFFORDABLE CONCRETE WALLS CAN BE IFIREOJSE the com, soybean meal, etc. plus what is supplemented from the premix. Com and soybean meal will add .another .10 ppm (for grower pigs and larger), bringing the total to roughly .20 ppm. So have we got a problem with the new rule? Certainly not with the starter pigs supplemental selenium levels for that phase of production remains at .3 ppm. But for older pigs we might, because of the second important issue in the table. There is no margin of safety. Fast growing pigs and heavy milking sows, many researchers argue, may be cut a little short But even at the new levels, finding reports of any obvious deficiency problems in the literature is difficult If supplemental selenium levels are to be .3 ppm for starter pigs, and .1 ppm for older pigs, what will happen? In most operations, nothing. A few producers with high perform ing herds may see some deficiency signs unthriftiness and pale skeletal and heart muscle upon post-mortem exam. If producers suspect problems are due to low dietary selenium, injectable selenium/vitamin E can be pre- Requirement, ppm scribed by a veterinarian. Or ingre dients with naturally high sele nium (alfalfa meal, fish meal, meat CONCRETE WALLS, INC. ♦ 601 Overly Grove Road. New Holland, PA 17557 •r The Worst Case and bone meal, com distiller’s) could be included in the diet. The Best Case For the FDA to suggest that we need to reduce the selenium in swine diets from a tiny amount to an even tinier amount because ducks can’t live in a seleniferous area is, in my opinion, almost silly. The list of items that are vital to life, but cause problems when con sumed in excess, would fill this publication. Oxygen and water are just two examples. Let’s hope that logic and com mon sense will prevail and that the FDA will soon reverse their deci sion to lower selenium levels. References Groce, A. W. et el. 1973. Selenium requirement! in com-ioy diets for growing finishing twine. J. Anim. Sci. 37:948. Mahan, D. C. etal. 1974. Efficacy of sup plemental selenium in reproductive diets on sow and progeny performance. J. Anim. Sci. 39:536. McMahon, Karen. 1994. Selenium at risk. National Hog Fanner. March 15,1994. pp 38-42. Meyer, W. R. et al. 1981. Value of diet ary selenium and vitamin E for weanling swine as measured by performance and tissue selenium and glutathione peroxidase activities. J. Anim. Sci. 52:302. Miller, H. R. 1989. Trace minerals. Feed Management. 40(2); 20-22, 30-31. Muirhead, Sarah. 1993. FDA stays 1987 selenium amendment Feedstuffs. Septem ber 20, 1993. pp 1. 7. Muirhead, Sarah. 1994. CAST paper supports higher selenium levels. Feedstuffs June 20, 1994. pp 1, 7. National Research Council. 1988. Nutri ent Requirements of Swine. Ninth edition. National Academy Press. Oldfield,!. E. 1990. Uses of selenium in agriculture, environment: An update. Feed stuffs November 5, 1990. pp 11-12, 18. Wilkinson, J. E. et al. 1977. Effects of supplemental selenium on swine. I. Gesta tion and lactation. J. Anim. Sci. 44:224. Siici i.ili/inf, In Manure Storage Rotuu 1 hi Rm tnnj'.nlai. II I ( il lUlllll (II Ahnvo (iinunil Vi; ' , CONTACT ROY SENSBNIG 717-365-0726
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