Magnesium and Sulfur

Magnesium is involved in what functions?

Bone, oxidative phosphorylation, enzyme activator (involve phosphatases, ATP)

Where can sources of magnesium be found?

• Grasses such as alfalfa

• Animal protein supplements

• MgO (55%)

• Grains (low in Mg)

Half of body Mg is found where?

In the bone

Magnesium can be found in cells where?

• Liver cells

• Skeletal muscle

• RBC

Where is magnesium absorbed?

Absorbed passively primarily in the ileum

A great percentage of Mg is excreted via _______.

Urine

What are the signs of a magnesium deficiency?

Hyperirritability, muscle twitching, weak and crooked eggs, tetany, mitochondrial swelling, reduced enzyme activity, necrosis of kidney, death

What occurs when there is a toxicity of magnesium?

Decreases acetylcholine, drops blood pressure, stops the heart while in diastole, excess Mg interferes with Ca and P

Why does magnesium cause a decrease in acetylcholine?

Excess magnesium paralyzes skeletal muscles by competing with calcium on the presynaptic membrane and inhibits calcium-dependent acetylcholine release

Magnesium in the _______ involved in phosphate transfer reactions

Co-factor

Magnesium chelates with what to form insoluble magnesium-phytate salt

Phytate

About _____ of the magnesium body supply is in the skeleton

70%

What percent of magnesium is distributed in body fluids/tissues?

30%

How much magnesium is found in blood?

2-3 mg/100 mL

How much skeletal magnesium can be mobilized to blood in case of reduction in dietary supply?

1/3

Magnesium helps with bone _______.

Formation

Magnesium is a cofactor used to change pyruvate to what during cellular respiration?

Acetyl CoA

Magnesium helps to _______ nerve irritability (similar to calcium)

Decrease

Where does absorption of magnesium occur in ruminants v.s. Non-ruminants?

• Non-ruminants: Ileum of small intestine

• Ruminants: Rumen

Soluble magnesium salts use what mechanism during absorption?

Active transport

High levels of ammonia (NH3) (from grazing lush spring grass) can _______ absorption of magnesium.

Dcrease

A ____ level of ammonia is favored for magnesium absorption.

Low

High nitrogen amounts in blood will ______ urinary magnesium excretion, while high potassium _______ absorption.

Increase; Decreases

Grass tetany is characterized by what 5 things?

1. low Mg levels in blood

2. Nervousness

3. Loss of appetite

4. Trembling (titanic muscle spasms)

5. Convulsions, coma, death

When does grass tetany occur and in who?

Occurs in cows and ewes who are turned out on lush pasture in the spring

Grass tetany is also known as:

Hypomagnesemia

How do you cure a magnesium deficiency?

• IV Ca and Mg-gluconate

• Feeding/supplying Mg

A magnesium deficiency in swine showed stepping syndrome. What is this?

The pig steps continuously while standing. Weakness of patterns was apparent. Due to neuromuscular hyperexcitability. Calcium will not properly be blocked, leading to overactive muscle contractions.

magnesium deficiency in lambs illustrated _________, causing stiff legs.

Unthriftiness

Convulsive seizure is characterized by what?

Magnesium “tetany”/ deficiency. Animal first illustrates hyperextension then by relaxation to rigidity and opisthotonos.

The body contains what percentage of sulfur?

0.15%

What two amino acids are involved in organic sulfur bonding?

Cystine and methionine

Wool is what percentage of sulfur due to sulfur contains amino acids?

4%

Majority of sulfur found in blood is found where?

• In plasma proteins

• Free amino acids (CYS and MET)

Sulfur is present in which 2 vitamins?

• Thiamine

• Biotin

A smalls mount of sulfur is found in what ion?

Inorganic sulfate ion (SO4-)

Besides amino acids, what other 2 organic compounds contain sulfur?

1. Insulin: Hormone that regulates blood sugar)

2. Glutathione (a reducing agent in metabolism)

Sulfur is present in chondroitin sulfate. What is this?

A constituent of cartilage

Sulfur nutrition is primarily a matter of _____ ______ nutrition.

Amino acid

Sulfur is typically absorbed in what form?

• Absorbed in organic form as cystine and methionine

• Some may occu as the sulfate form nd hydrogen sulfide

Where is sulfur absorbed?

Small intestine

What are the two ways sulfur is excreted?

1. Urine

2. Feces

What is the form of sulfur that is excreted in feces?

Organic sulfur; amino acids

What is the primary form of sulfur as it is excreted in urine?

Excreted as inorganic sulfate (SO4-). This is the final oxidation product of organic sulfur

What are the 3 forms of sulfur that is exerted in the urine?

1. Inorganic sulfate (SO4-)

2. Ethereal sulfur

3. Neutral Sulfur

Ethereal sulfur is excited in urine. What is this compound present in?

Ethereal sulfur is present in complex detoxification compounds

What 3 neutral sulfur compounds are excreted in urine?

1. Cystine

2. Taurine

3. Thiosulfates

Why do you not have to consider S when feeding natural proteins to ruminants?

Due to the high content of sulfur containing amino acids in their diet

Other sulfur forms in the body can be derived from what?

Amino acid metabolism

In general is sulfur supplemented?

No, sulfur is not considered when supplementing rations

Providing what amino acid provides for the total sulfur needs since most of it is used as amino acids

Methionine (MET)

Additional sulfur will be beneficial for microbial synthesis of sulfur amino acids in what diet and in what species?

NPN (urea) for ruminants