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COBALT

By: Larry L. Berger, Ph.D University of Illinois
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Cobalt in Ruminant Nutrition

As early as 1935, Australian researchers associated cobalt with coast disease of sheep and wasting disease of cattle.

However, it wasn't until 1948 that cobalt was recognized as essential for vitamin B12 synthesis. More recently results of several studies suggest that cobalt may improve fiber digestion in the rumen independent of its role as part of vitamin B12. Following is a review of our current understanding of the nutrient, cobalt.

Ruminants vs. Monogastrics
The reason ruminants responded to cobalt supplementation and monogastric animals showed no response was a mystery for many years.

When it was recognized that cobalt was 4.4% of the molecular weight of vitamin B12 and that rumen bacteria could efficiently synthesize B12, these differences started to make sense. Cobalt deficiency in ruminants leads to a vitamin B12 deficiency that is corrected with cobalt supplementation. Because monogastric animals do not have a bacterial population in the gut that can synthesize sufficient vitamin B12, cobalt supplementation is ineffective. Monogastric animals must have vitamin B12 in their diet or practice coprophagy to prevent a deficiency. In the wild, ingestion of feces is common among monogastric animals. Many of the B vitamins including B12 are synthesized as a result of bacterial fermentation in the large intestine, but B12 is excreted because it must be bound by an intrinsic factor produced in the stomach before it can be absorbed. Coprophagy is one means of obtaining the B vitamins that are deficient in the basal diet. Clear evidence of a cobalt requirement independent of the B12 requirement has not been documented in monogastric animals. Ruminant feces are an excellent source of vitamin B12. In the 1930s, it was observed that feeding pigs and cattle together in the same pen improved the health and performance of the pigs, if they were not fed animal proteins. We now know that pigs on plant-based diets were deficient in vitamin B12. When cattle and pigs were in the same pen, the pigs pick up enough B12 from the cattle feces to prevent the deficiency.
GW Note: I have observed that swine kept with cattle do keep the pens cleaner as well as provide for a markedly, thriftier pig. However, one should use caution in this practice during calving season.

Synthesis of vitamin B12 by rumen or other bacteria is amazing, as it is one of the most complex non-polymeric natural products produced in nature. The general formula for vitamin B12 is C63H88N14O14PCo with molecular weight of 1355. Ruminal synthesis of B12 is dramatically increased within hours of cobalt supplementation of a deficient diet. Suttle et al. (1989) reported that ruminal B12 synthesis increased quadratically, being proportional to the square root of the dose between 1 and 32 mg of cobalt per head in sheep. A 10 mg dose resulted in approximately three times greater B12 synthesis than a 1 mg dose. In general high forage diets and high levels of intake favor B12 synthesis in ruminants.

Signs of Cobalt Deficiency:
When ruminants are on a cobalt deficient diet, there is a gradual loss of appetite, weight loss, muscle wasting, depraved appetite, anemia, and eventually death (Underwood and Suttle, 1999). The animals appear as if they have been starved, except that the visible mucus membranes are blanched and the skin is pale and fragile. Secondary signs of a cobalt deficiency include fatty liver, increased mortality of offspring shortly after birth, increased susceptibility to infectious agents and infertility.

The rapid loss of appetite in cobalt deficient ruminants is not nearly as obvious in vitamin B12 deficient monogastric animals. Monogastric energy metabolism is based on glucose absorbed from the small intestine, while ruminants get approximately 70% of their metabolizable energy from volatile fatty acids produced in the rumen. Acetate, propionate and butyrate are the main volatile fatty acids utilized for energy. Normal propionate metabolism requires vitamin B12. Accumulation of propionate in the blood rapidly depresses appetite (Farningham and Whyte, 1993), and there is an inverse relationship between feed intake and propionate clearance in cobalt-deficient sheep (Marston et al., 1972).

Cobalt and Rumen Bacteria:
Recent Irish research suggests that cobalt deficiency may directly affect the metabolism of rumen bacteria which in turn may affect the digestion process. Kennedy et al. (1991) reported large increases in succinate concentration in rumen fluid within two weeks after sheep were fed a cobalt- deficient barley-based diet. They suggested that propionate producing bacteria like Selenomonas ruminantium may be especially susceptible to a cobalt deficiency. In 1996 Kennedy et al. reported that succinate concentrations increased within two days after being fed a diet containing 0.02 ppm cobalt, but not when 0.04 ppm cobalt was present. Florida researchers also reported rapid changes in the rumen microbial population of animals grazing cobalt-deficient forages (Gall et al., 1949).

Lopez-Guisa and Satter (1992) reported that cobalt supplementation above that required for B12 synthesis may improve the utilization of poor quality forages. The rate of fiber digestion in the rumen is a major factor affecting voluntary intake on high forage diets. Supplementation of cobalt above animal requirements may increase the ability of bacteria to digest fiber. Divalent cations such as cobalt may allow bacteria to connect to plant cell walls. The cellulose enzymes produced by bacteria are retained on the cell membrane and are not released into the environment. Consequently, the bacteria must physically attach to the fiber particle for the enzymes to digest the cellulose. It appears that when a negatively charged bacteria has difficulty attaching to a negatively charged fiber particle, cobalt with two positive charges can serve as a means of linking the two surfaces (Lopez-Guisa and Satter, 1992). In one experiment, cobalt increased the rate of in situ corn fiber digestion from 3.4 to 6.2% per hour. In other experiments cobalt supplementation above that required by the animal increased volatile fatty acid concentrations in the rumen fluid (Gridin, 1986), suggesting that the rate of fiber digestion was improved.

Cobalt Supplementation:
Forages containing less than 0.07 ppm cobalt require supplementation (Underwood and Suttle, 1999). Inorganic sources of cobalt must be soluble in the rumen to allow bacteria to incorporate cobalt into vitamin B12. Cobalt oxide has lower nutritive value than equal amounts of cobalt from more soluble sources such as cobalt carbonate or cobalt sulfate (Ammerman et al., 1982).

Cobalt Deficient Areas:
As shown in the map, cobalt deficiency has been reported in over 15 states throughout the United States. Florida and the eastern seaboard states all the way to Maine have reported cobalt deficiencies. In the upper Midwest, parts of Michigan, Wisconsin, Minnesota, Iowa, Missouri and Nebraska produce feeds low in cobalt. Feedstuffs produced in these areas are often shipped to other states that are considered cobalt adequate. Consequently, cobalt supplementation of all ruminant diets throughout the US is recommended.

Summary:
Cobalt is essential in ruminant diets for the synthesis of vitamin B12. Cobalt may also be beneficial in ruminant diets as a means of improving the efficiency of fiber digestion by bacteria. Although cobalt requirements are less than 1 ppm in the diet, cobalt deficiency has devastating effects on animal health. Feeding a well fortified trace mineralized salt containing cobalt is the best means of insuring that animals get adequate cobalt nutrition.

Persons that read this article were also interested in reading:
Cobalt (Sulfate) by the Salt Institute,
Selenium...The Facts by Larry L. Berger, Ph.D University of Illinois, and
Nutrition Product Reference Guide by Gary Pfalzbot, GoatWorld.

About the author: No information is available.

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