Animals
Nutrition


Iodine (I) is an essential component of proteins produced by the thyroid. It is therefore important for maintaining the proper functioning of the thyroid gland. Iodine promotes healthy growth and development of young animals. An enlarged thyroid gland (goitre) is evidence of a prolonged iodine deficiency. Young animals that are iodine deficient develop less vigorously, because of reduced bone development, among other things.

 

Selenium is another trace mineral that plays a role in synthesis of the thyroid gland hormones. High iodine intake combined with low selenium intake can reduce the productivity of the thyroid gland hormones, similar to the effect of an iron deficiency. Iodine is mainly stored in the thyroid gland, though it is also found in high concentrations in the ovaries, the lymph nodes and the salivary glands. Stored quantities can be drawn upon in the event of a deficiency, so animals are not quick to be iodine deficient. Excretion of iodine occurs mainly via the urine.

 
Animal with an abnormally large thyroid gland (goiter) (photo Susan Schoenian) 

Animal with an abnormally large thyroid gland (goiter) (photo Susan Schoenian)
 
 
Observable signs of a deficiency or excess of iodine (source: Akzo Nobel)
Animal Species Observed symptoms of a deficiency Observed symptoms of an excess
Cattle -Goitre
-Diminished bone growth
-Diminished milk and meat yield
-Weak or still-born calves
-Blind calves
-Hairless calves
-Reduced fertility
-Reduced appetite
-Excess tearing and salivation
-Nasal discharge
-Rapid breathing and coughing
Sheep -Goitre
-Lamb mortality
-Weak lambs
-Reduced appetite
-Excess tearing and salivation
-Nasal discharge
-Rapid breathing and coughing
Goats -Goitre
-Lamb mortality
-Weak lambs
-Abnormalities in coat
-Reduced appetite
-Excess tearing and salivation
-Nasal discharge
-Rapid breathing and coughing
Horses -Dull and/or rough coat
-Thyroid gland abnormalities
-Hair loss
-Slow shedding
-Weak or still-born foals
-Swollen limbs
– Still births
– Hair loss
– Lethargy
– Fat deposition

 
 

Cattle

In ruminants, iodine is absorbed primarily in the rumen and in the intestines. Absorption is very efficient, sometimes reaching more than 80 per cent. Dairy cows have a higher iodine requirement than beef cattle because they excrete some 10 per cent of their iodine intake via the milk. Colostrum is particularly high in iodine. Deficiencies cause abnormalities in the thyroid gland. Symptoms in beef cattle may also include blind and hairless (still-born) calves. Prolonged deficiencies may cause diminished production and reproduction.

Sheep and Goats

Even though iodine absorption is very efficient in the gastrointestinal tract of sheep, iodine needs are not always met by dietary intake. A deficiency can manifest in the form of an enlarged thyroid gland, but also in weak or still-born lambs and lower milk production in ewes. Some plants have a suppressive effect on the functioning of the thyroid gland. In goats deficiencies seldom occur.

Horses

In horses, iodine is an important trace element for regulation of the metabolism. In adult horses, symptoms of an iodine deficiency are a dull or rough coat. The shedding process may also be slower in iodine-deficient animals, and hair loss may be patchy. An iodine deficiency in pregnant mares can result in weaker foals or foals with thyroid gland abnormalities.
 
In horses, seasonal shedding is dependent on iodine status, among other things

In horses, seasonal shedding is dependent on iodine status, among other things