Answers to Frequently Asked Questions
by Larry L. Berger, Ph.D.
Professor, Animal Sciences
University of Illinois
Q. Q.
Does the form of the copper, zinc and manganese in my trace mineral supplement have
much effect on bioavailability?
A. A.
Yes, generally organic complexes have the highest, followed by the sulfate forms, with the
carbonates and oxides being the lowest.
Q.
Why can’t I buy individual trace
minerals to feed rather than a mixture with salt?
A. A.
The answer seems to be “why shouldn’t” rather than “why can’t”. I’d suggest changing “can’t”
to “shouldn’t” or changing the answer to state why sellers of trace
minerals don’t sell then unless mixed with salt (e.g. unpalatable separately, only
small amounts required, etc.)
Q.
Q. Can fertility problems in a dairy herd be related to
trace mineral nutrition?
A.
A. Yes, copper, zinc, selenium, cobalt and manganese have
all been shown to depress fertility when deficient.
Q. What is the best means of determining the iodine status of sheep?
A. Most of the iodine in the body is in the thyroid gland. Because iodine is required for thyroxine synthesis, the two are highly correlated. Measuring serum thyroxine is the best indicator of iodine status.
Q. I bought a trace mineral salt block for my sheep
that contains 320 ppm of copper. I have been told that sheep can get copper toxicity with
levels as low as 10 ppm in the diet. How much
will this increase the copper concentration in the total diet?
A. It depends on the salt intake. Seldom will sheep eat over 1% of their diet as salt from a block. If the sheep ate 1%, it would add 3.2 ppm (320/100) of copper to the diet.
Q. Can trace mineral deficiencies cause vaccines to be ineffective in feedlot cattle?
A. Deficiencies of copper, zinc, and selenium have been shown to impair immune function. These trace minerals are required to allow antibodies to attack and destroy invading pathogens. When these minerals are deficient you may not get a full response to vaccination.
Q. Does zinc source affect zinc bioavailability?
A. Recent Illinois research with chicks showed
that most zinc sulfate sources were similar in bioavailability, whereas feed-grade zinc
oxide sources were more variable and tended to have a lower availability.
Q. Is there a difference in the
bioavailability of zinc from different source for broilers?
A. Illinois researchers recently compared the
bioavailability of four zinc oxide, two zinc metal, and two zinc sulfate sources in
broiler diets. When zinc sulfate
bioavailability was set to 100%, the zinc oxides averaged 74.9% and zinc metals 40.0%.
Q. Is there anything I can do to improve the
palatability of my salt-magnesium oxide mixture fed free-choice to prevent grass tetany?
A. One approach that has increased intake is to add a
palatable third ingredient such as dry molasses, cracked corn or soybean meal. The final mixture will be equal parts trace
mineral salt, magnesium oxide, and palatable ingredient.
Q. What is the sodium requirement of the laying hen?
A. Recent Florida research compared eight diets
containing between 0.056 and 0.21% salt for laying hens.
Decreasing the daily sodium intake below 110 mg/hen decreased egg production
beginning the second week.
Q. Will exercise increase the appetite for salt in
the performing horse?
A. Although not
specifically documented with horses, recent experiments with
humans found that those who
routinely exercised one hour per day, preferred tomato soup with a higher salt
concentration compared to people who did not exercise.
Q. Can excess molybdenum
effect the immune function of cattle?
A. Recent research from
Argentina shows that Angus cattle fed a diet containing 5 ppm molybdenum had reduced
copper and zinc superoxide dismutase and cytochrome c oxidase activities in leukocytes. This can impair the immune system and make cattle
more susceptible to infections.
Q. Is there any relationship between somatic cell
count in dairy cows and sodium intake?
A. Yes, there can be. British studies where cows were grazing perennial
ryegrass containing less than 1.0 g of sodium per kg dry matter, sodium supplementation to
increase dietary sodium to 6.0 g/kg dry matter reduced the somatic cell count.
Q. Is there any research demonstrating interactions
when animals are moderately deficient in trace minerals and B vitamins simultaneously?
A.
Yes, Illinois research showed that in the growing chick a combination of
zinc and riboflavin or pyridoxine deficiency had a greater depression in performance than
any single nutrient.
Q. Can salt level in the diet affects the frequency
of abnormal behavior in confined animals?
A.
Recent British research showed that adding salt to supply between 4 and 9
grams of sodium/kg diet reduce the incidence of ear sucking, licking of the pens and food
buckets, and self-grooming in six-week old calves.
Q. Will horses increase their salt intake in response
to intense exercise if they have free choice salt blocks available?
A. Not necessarily, recent research with Standard bred horses showed that salt consummation did not increase to cover the increase requirement for exercising. Adding 0.5 to 1.0% salt to the grain mix in addition to providing a salt block is probably the safest approach.
Q. Do sodium and potassium have a role in preventing legume bloat in cattle?
A. Recent Canadian research has demonstrated that bloat-prone animals have lower ruminal sodium and higher potassium concentrations than less susceptible animals. This shift in ionic equilibrium may contribute to the occurrence of bloat through colloidal aggregation of chloroplast particles. The benefits of increase sodium intake to reduce this problem needs to be evaluated.
Q. Can excess calcium or phosphorus affect manganese utilization by chickens?
A. Yes, studies conducted at the University of Illinois showed that feeding .88% excess inorganic phosphorus, alone or in combination with excess calcium, reduced manganese utilization by 50-65%. These trials showed that excess phosphorus is more antagonistic to manganese than is excess calcium.
Q. Are there situations where tin is an essential nutrient?
A. Recent research suggests that tin plays an essential role in the stimulation of the thymus gland. Enhanced immune function is often obtained in the presence of tin. Experiments to determine the practical benefits of adding tin to livestock and poultry diets has yet to be done.
Q. Can feeding rapeseed meal containing high levels of glucosinolate affect the trace mineral nutrition of livestock?
A. Yes, German researchers have shown that feeding 8.8% rapeseed meal containing 5.5% glucosinolates caused an iodine deficiency and reduced blood zinc concentrations in pigs. Additional trace mineral supplementation is indicated when the diet is high is glucosinolates.
Q. Is there any evidence that glucose tolerance factor chromium could be beneficial to ruminants?
A. Yes, researchers at the University of Guelph added glucose tolerance factor chromium to the diets of stressed feeder cattle. Cattle receiving 4 mg chromium per day gained faster and consumed more feed. The supplemental chromium caused decreased serum cortisol and improved immune status.
Q. I have heard that chromium supplementation can reduce shipping stress in feeder cattle. Should I be supplementing my receiving diets?
A. Recent research at the University of Guelph does show that chelated chromium can reduce shipping stress in feeder cattle. However, the FDA has not cleared any chromium source to be added to cattle feeds at the present time. It is probable that chromium sources will be cleared in the future
Q. Can trace mineral deficiencies affect the birthing process?
A. Yes. Recent data in sheep, pigs and rats has shown that zinc deficiency can result in prolonged labor, retained placentas and an increased number of stillborns. These symptoms can occur without other signs of zinc deficiency. Feeding a well fortified trace mineralized salt should prevent zinc deficiency.
Q. Are most natural sources of selenium readily available?
A. There are few data available with animals but some recent work with humans suggest that bioavailability may vary. Research from Norway compared availabilities of selenium in fish and wheat. Platelet selenium increased 30% for those people eating the wheat products but decreased 11% for those consuming a similar amount of selenium in fish. The reason for apparent differences in availability are not clear.
Q. Can the zinc requirement of pigs be affected by the supplemental protein source.
A. Yes. Recent British research has shown that as the level of canola meal in the diet increased there was a decrease in the amount of zinc absorbed. The authors believed that the high phytate content of the canola meal was the cause of the reduced zinc absorption by the pigs.
Q. Can high iron intakes of grazing animals cause a mineral imbalance.
A. It is unlikely. Recent research at North Carolina showed that feeding sheep as high as 1,200 mg iron/kg diet did not affect zinc status. Zinc is thought to be the mineral most affected by excessive iron intakes.
Q. Will grazing animals respond to sodium fertilization if the soils are known to be sodium deficient?
A. Recent research from Wales has shown that applying sodium fertilizer to pastures for dairy cows increased grass growth and digestibility. In addition, cows found the sodium-enriched forage to be more palatable, grazed for longer periods and produced more milk. Additional information can be obtained from the January 11, 1993 Feedstuffs Vol. 65 No. 2. p. 13.
Q. Can subclinical trace element deficiencies cause animals to be more susceptible to various endotoxins?
A. It is difficult to find any studies with farm animals. However, recent Ohio State research showed that rats which were copper deficient had antioxidant enzymes with lower activities, resulting in weakened resistance against endotoxin-induced injury.
Q. How can I know if supplemental manganese is needed for my pigs?
A. The following requirements (mg/day) for manganese have been determined by Russian researchers: birth-2 months, 1.14; 2-4 months, 2.3; 4-6 months, 3.6; and 6 months and older, 4.1. Supplemental manganese is present in trace mineralized salt for pigs and is cheap insurance.
Q. Is it true that selenium deficient animals are more susceptible to infectious diseases.
A. Yes, recent research from Penn State showed that selenium deficient cows had slower lymphocyte proliferation when challenged by an infectious agent. These data suggest that a cow's immune system is a weaker line of defense when she is selenium deficient.
Q. Can high sulfate levels in the drink water affect the mineral requirements of livestock.
A. Yes, sulfur can reduce the bioavailabilty of zinc, copper, selenium and molybdenum. Both the concentration and form of the sulfate in the drink water can affect mineral metabolism.
Q. What is the bioavailability of iodine in iodized salt?
A. A recent French study with humans showed that approximately 92% of the iodine was absorbed. These data suggest that the bioavailability of iodine is very high and that iodized salt is an excellent delivery method.
Q. With the FDA imposed reduction in dietary selenium levels, should I increase dietary vitamin E since they are both antioxidants?
A. Even though they are both antioxidants, they have different sites of action. Vitamin E acts on the biomembranes while selenium-dependent glutathione peroxidase acts in the cytoplasm. Vitamin E tends to be most effective in preventing lipid peroxidation while selenium is more effective in preventing free radical production. The benefits of increasing vitamin E are doubtful if you are feeding the maximum allowable level of selenium.
Q. Is there evidence that the zinc requirement increases with age in the horse?
A. There is little data with the horse, but recent data with mice show that increasing zinc intakes in aged mice increased the activity of the thymus gland and enhanced the immune system. Research is needed to determine if the same response occurs in aged mares.
Q. Is there evidence that offspring born to a copper deficient mother can have permanent central nervous system problems?
A. Yes, recent Minnesota research with mice showed that perinatal brain development was affected by copper concentration in the mother diet. Mice born to copper deficient dams had permanent brain disorders even when fed adequate copper after birth.
Q. Can salt be used to control spoilage on the top and edges of bunker silos?
A. Yes. British researchers have shown that spreading one pound of salt per square foot, before covering the silo with plastic, nearly eliminated surface spoilage. This can be a dramatic saving in feed, since spoilage losses can exceed 20% of the dry matter in many bunker silos.
Q. Does pregnancy in farm animals increase selenium requirement?
A. Selenium requirement during pregnancy has been difficult to measure in farm animals. However, recent research with rats show that there is a considerable transfer to the fetus via the placenta. This could be the reason that subsequent fertility is often impaired in marginally selenium deficient livestock.
Q. What level of zinc should be in milk replacers for veal calves and what would be the first deficiency symptoms?
A. The 1989 Dairy NRC suggest 40 ppm zinc in milk replacers. Recent German research showed that when 7 ppm zinc was fed the first deficiency symptom was a 25% decrease in growth rate.
Q. What is the relative bioavailability of copper-lysine and copper sulfate for poultry?
A. Recent research from the University of Florida with chicks showed that the bioavailabilities were very similar with values of 99 and 100% for copper-lysine and copper sulfate, respectively.
Q. Does source of supplemental protein affect the iron requirement of fish?
A. It can depending on the protein source. Japanese researchers reported that soy proteins tended to increase the iron requirement compared to brown fish meal. However, adding iron to soy protein increased serum iron concentrations.
Q. Does adding ascorbic acid to the diets of poultry to help with heat stress have any effect on trace mineral requirements?
A. It probably depends how long and at what level the ascorbic acid is added. Researchers have reported that adding ascorbic acid at the rate of 10 g/kg of diet will deplete liver copper stores in rats. This possibility should be investigated in broilers.
Q. Can zinc levels in the diet influence fertility in rams?
A. Recent Australian research shows that rams fed diets deficient in zinc have reduced testosterone synthesizing capacity and impaired development of the seminiferous tubules. These changes can reduce libido and fertility of the rams.
Q. Does adding sugar to creep diets of the young pig to increase intake affect mineral absorption?
A. I do not know of data with pigs, but a recent trial in the Netherlands with rats suggest that replacing glucose with fructose caused a significant reduction in iron absorption from the small intestine. Anemia is already a potential problem in the young pigs, so caution is recommended.
Q. Are the trace minerals in cereal grains readily absorbed by poultry?
A. It probably depends on the mineral. Recent German research showed that the zinc and manganese bioavailabilities for corn, barley, wheat and oats were around 50%. In comparison, copper bioavailabilities were in the 75% range for the same grains.
Q. Does fertilizing forages with salt have any effect on the potassium concentrations in the forage?
A. Yes it can, depending on the type of forage and the soil potassium level. Recent British research showed that applying salt (50 lbs/acre) to perennial ryegrass pastures decreased forage potassium levels and increased forage sodium levels. This would be especially helpful to dairy farmers trying to reduce potassium levels in their dry cow diets. Excess potassium has been associated with milk fever and udder edema.
Q. How much salt should I add to a grain mix to limit intake to approximately three pounds per day for grazing steers?
A. It depends on the size of the steers and the quantity and quality of the forage. I suggest starting with 10% salt and then monitoring feed intake. Salt concentration must commonly be increased 3% to 5% as the cattle adapt to it and the forage matures.
Q. Does breed of cattle affect trace mineral requirements?
A. Yes, breed can have a significant effect. For example, Simmentals and Charolais cattle have a higher copper requirements than Angus because they are less efficient absorbers of copper from the small intestine.
Q. Does trace mineral supplementation of diets for yearling colts affect subsequent performance.
A. Recent Texas research showed that a complete trace mineral package did increase bone deposition in the yearling. How this affects subsequent performance was not measured. However, soundness of feet and legs is critical for maximum performance and so it could have an indirect effect.
Q. What level of zinc is required for the early weaned pig?
A. Recent research summarized across seven universities showed that 2,000 ppm zinc from zinc oxide increased feed intake, growth rate and feed efficiency. At least part of the response is due to an "antibiotic" effect.
Q. Will salt levels in feedlot diets affect dry matter intake?
A. It can, depending on the level of addition. Oklahoma researchers fed feedlot heifers diets that contained 0.0, 0.25 and 0.50% salt. Dry matter intake increased from 8.9 kg/day to 10.2 and 10.4 kg/day with the 0.25 and 0.50% salt additions.
Q Can the type of housing affect copper levels in sheep?
A. Recent Irish research show that lambs fed on expanded metal flooring had higher liver copper stores than lambs fed the same diet housed in earthen pens bedded with straw. Although there were no differences in lamb performance, this research shows how numerous factors can affect liver copper stores in sheep.
Q. When a feed analysis gives the "salt content" does it include only the sodium plus chloride concentration?
A. Probably not; most likely it includes the "total salts" concentration which is the sum of the soluble calcium, potassium, magnesium, sodium, chloride, sulfate, nitrate and borate.
Q. Which minerals should I be concerned with to prevent grass tetany in my lactating beef cows?
A. The best way to prevent grass tetany is to feed free-choice a mixture of equal parts magnesium oxide: trace mineral salt and grain (corn, barley, etc) beginning two weeks before the cows are turned out to pasture. The disease is caused by excess potassium in the forage which prevents magnesium absorption. Magnesium oxide will provide the magnesium and the salt will increase the sodium:potassium ratio in the rumen which improves magnesium absorption.
Q. Can I use a trace mineralized salt designed for beef cattle to feed my 4-H lambs?
A. It depends on the copper level in the trace mineral salt and the diet you are feeding. To be safe, the total diet for sheep should be under 10 ppm copper. Sheep are more susceptible to copper toxicity at levels which may just meet the needs of cattle.
Q. Do horses exhibit "nutritional wisdom"? When given a choice will they select the appropriate amounts of each mineral, if I offer a variety of mineral sources cafeteria style?
A. Generally, animals do not have the ability to consume only the amount required to meet their need for given minerals. Also, many of the pure mineral forms are not very palatable, and will not be consumed readily unless mixed with the other feedstuffs. It is more likely your horse will get the balanced nutrition you desire if you feed a balanced mineral supplement mixed with the rest of the diet.
Q. Does particle size affect salt’s ability to act as an intake regulator for free-choice supplements being fed to cattle while grazing?
A. Yes. Usually a finer grind of salt work best. This is especially true if the supplements are in the meal form. If the supplement is pelleted, salt particle size may not make much difference.
Q. Does feeding high levels of copper have the same growth promoting effects in poultry as in swine?
A. Recent research in Egypt showed that feeding copper sulfate at 150 ppm improved daily weight gain and feed efficiency in broilers. However, when copper carbonate or copper oxide was fed at the same concentration there was no response. Histological examination of the small intestine suggests that copper sulfate resulted in a healthier intestinal lining with a more absorptive surface.
Q. Does feeding supplemental zinc to pregnant cows affect the zinc stores in the calf after birth?
A. Yes, it can. Research conducted by the USDA at Miles City showed that feeding 170 mg of zinc per day during the last trimester of gestation significantly increased the plasma zinc levels of the calves even after six weeks of age. They concluded that there was a transfer of zinc in utero and that the transfer from the cow to the calf may have continued after birth via the milk.
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