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<p style="margin-top: 0.1pt; margin-right: 0cm; margin-bottom: 0.1pt;"><strong>B-vitamins are a group of 8 water soluble vitamins that play important roles in cell metabolism. They can not be produced by the body itself, but can be produced by bacteria, fungi and plants. In the horse, microorganisms in the gut (mainly the hind gut) are capable of synthesizing B-vitamins.&nbsp;Equine nutrient requirements have only been established for thiamin (B1) and riboflavin (B2). In this article we will look at the function, dietary sources and requirements for thiamin (vitamin B<sub>1</sub>).</strong></p>
<p><img style="vertical-align: middle;" src="images-joomla/stories/seasons/ax.jpg" alt="ax" /> <img style="vertical-align: middle;" src="images-joomla/stories/seasons/tiaminformel.png" alt="tiaminformel" /></p>
<p><strong>Function<br /></strong>Thiamin is a vitamin that plays vital roles in the energy metabolism. It is needed when carbohydrates, fats and proteins are used for production of the high energy compound ATP and for the production of pentose sugars (ribulose) needed for the production of the nucleic acids DNA and RNA.</p>
<p><strong>Dietary sources<br /></strong>Thiamin is found in relatively high concentrations in cereal grains and byproducts (see table).</p>
<table style="border-collapse: collapse;" border="1" cellspacing="0" cellpadding="0">
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<td style="width: 91.9pt; border: 1pt solid windowtext; padding: 0cm 5.4pt;" valign="top" width="92">Corn</td>
<td style="width: 4cm; border-width: 1pt 1pt 1pt medium; border-style: solid solid solid none; border-color: windowtext windowtext windowtext -moz-use-text-color; padding: 0cm 5.4pt;" valign="top" width="113">3.5 mg/kg DM</td>
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<td style="width: 91.9pt; border-width: medium 1pt 1pt; border-style: none solid solid; border-color: -moz-use-text-color windowtext windowtext; padding: 0cm 5.4pt;" valign="top" width="92">Oats</td>
<td style="width: 4cm; border-width: medium 1pt 1pt medium; border-style: none solid solid none; border-color: -moz-use-text-color windowtext windowtext -moz-use-text-color; padding: 0cm 5.4pt;" valign="top" width="113">5.2 mg/kg DM</td>
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<td style="width: 91.9pt; border-width: medium 1pt 1pt; border-style: none solid solid; border-color: -moz-use-text-color windowtext windowtext; padding: 0cm 5.4pt;" valign="top" width="92">Wheat</td>
<td style="width: 4cm; border-width: medium 1pt 1pt medium; border-style: none solid solid none; border-color: -moz-use-text-color windowtext windowtext -moz-use-text-color; padding: 0cm 5.4pt;" valign="top" width="113">5.5 mg/kg DM</td>
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<td style="width: 91.9pt; border-width: medium 1pt 1pt; border-style: none solid solid; border-color: -moz-use-text-color windowtext windowtext; padding: 0cm 5.4pt;" valign="top" width="92">Barley</td>
<td style="width: 4cm; border-width: medium 1pt 1pt medium; border-style: none solid solid none; border-color: -moz-use-text-color windowtext windowtext -moz-use-text-color; padding: 0cm 5.4pt;" valign="top" width="113">5.7 mg/kg DM</td>
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<td style="width: 91.9pt; border-width: medium 1pt 1pt; border-style: none solid solid; border-color: -moz-use-text-color windowtext windowtext; padding: 0cm 5.4pt;" valign="top" width="92">Wheat bran</td>
<td style="width: 4cm; border-width: medium 1pt 1pt medium; border-style: none solid solid none; border-color: -moz-use-text-color windowtext windowtext -moz-use-text-color; padding: 0cm 5.4pt;" valign="top" width="113">8.0 mg/kg DM</td>
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<td style="width: 91.9pt; border-width: medium 1pt 1pt; border-style: none solid solid; border-color: -moz-use-text-color windowtext windowtext; padding: 0cm 5.4pt;" valign="top" width="92">Wheat middlings</td>
<td style="width: 4cm; border-width: medium 1pt 1pt medium; border-style: none solid solid none; border-color: -moz-use-text-color windowtext windowtext -moz-use-text-color; padding: 0cm 5.4pt;" valign="top" width="113">12.0 mg/kg DM</td>
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<td style="width: 91.9pt; border-width: medium 1pt 1pt; border-style: none solid solid; border-color: -moz-use-text-color windowtext windowtext; padding: 0cm 5.4pt;" valign="top" width="92">Rice bran</td>
<td style="width: 4cm; border-width: medium 1pt 1pt medium; border-style: none solid solid none; border-color: -moz-use-text-color windowtext windowtext -moz-use-text-color; padding: 0cm 5.4pt;" valign="top" width="113">23.0 mg/kg DM</td>
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<td style="width: 91.9pt; border-width: medium 1pt 1pt; border-style: none solid solid; border-color: -moz-use-text-color windowtext windowtext; padding: 0cm 5.4pt;" valign="top" width="92">Brewer’s yeast</td>
<td style="width: 4cm; border-width: medium 1pt 1pt medium; border-style: none solid solid none; border-color: -moz-use-text-color windowtext windowtext -moz-use-text-color; padding: 0cm 5.4pt;" valign="top" width="113">95.2 mg/kg DM</td>
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</table>
<p>These concentrations of thiamin in feeds will will decrease during storage.<br />Thiamin is included in most concentrate mixtures for horses (10 – 20 mg/kg) and in vitamin supplements.</p>
<p><strong>Requirements</strong></p>
<p>The NRC 2007 gives requirements for thiamin for horses (see table).</p>
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<td style="width: 106.1pt; border: 1pt solid windowtext; padding: 0cm 5.4pt;" valign="top" width="106">Maintenance</td>
<td style="width: 5cm; border-width: 1pt 1pt 1pt medium; border-style: solid solid solid none; border-color: windowtext windowtext windowtext -moz-use-text-color; padding: 0cm 5.4pt;" valign="top" width="142">0.06 mg/kg body weight</td>
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<td style="width: 106.1pt; border-width: medium 1pt 1pt; border-style: none solid solid; border-color: -moz-use-text-color windowtext windowtext; padding: 0cm 5.4pt;" valign="top" width="106">Light exercise</td>
<td style="width: 5cm; border-width: medium 1pt 1pt medium; border-style: none solid solid none; border-color: -moz-use-text-color windowtext windowtext -moz-use-text-color; padding: 0cm 5.4pt;" valign="top" width="142">0.06 mg/kg body weight</td>
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<td style="width: 106.1pt; border-width: medium 1pt 1pt; border-style: none solid solid; border-color: -moz-use-text-color windowtext windowtext; padding: 0cm 5.4pt;" valign="top" width="106">Moderate exercise</td>
<td style="width: 5cm; border-width: medium 1pt 1pt medium; border-style: none solid solid none; border-color: -moz-use-text-color windowtext windowtext -moz-use-text-color; padding: 0cm 5.4pt;" valign="top" width="142">0.113 mg/kg body weight</td>
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<td style="width: 106.1pt; border-width: medium 1pt 1pt; border-style: none solid solid; border-color: -moz-use-text-color windowtext windowtext; padding: 0cm 5.4pt;" valign="top" width="106">Heavy exercise</td>
<td style="width: 5cm; border-width: medium 1pt 1pt medium; border-style: none solid solid none; border-color: -moz-use-text-color windowtext windowtext -moz-use-text-color; padding: 0cm 5.4pt;" valign="top" width="142">0.125 mg/kg body weight</td>
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<td style="width: 106.1pt; border-width: medium 1pt 1pt; border-style: none solid solid; border-color: -moz-use-text-color windowtext windowtext; padding: 0cm 5.4pt;" valign="top" width="106">Very heavy exercise</td>
<td style="width: 5cm; border-width: medium 1pt 1pt medium; border-style: none solid solid none; border-color: -moz-use-text-color windowtext windowtext -moz-use-text-color; padding: 0cm 5.4pt;" valign="top" width="142">0.125 mg/kg body weight</td>
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<td style="width: 106.1pt; border-width: medium 1pt 1pt; border-style: none solid solid; border-color: -moz-use-text-color windowtext windowtext; padding: 0cm 5.4pt;" valign="top" width="106">Pregnant mares</td>
<td style="width: 5cm; border-width: medium 1pt 1pt medium; border-style: none solid solid none; border-color: -moz-use-text-color windowtext windowtext -moz-use-text-color; padding: 0cm 5.4pt;" valign="top" width="142">0.06 mg/kg body weight</td>
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<td style="width: 106.1pt; border-width: medium 1pt 1pt; border-style: none solid solid; border-color: -moz-use-text-color windowtext windowtext; padding: 0cm 5.4pt;" valign="top" width="106">Lactating mares</td>
<td style="width: 5cm; border-width: medium 1pt 1pt medium; border-style: none solid solid none; border-color: -moz-use-text-color windowtext windowtext -moz-use-text-color; padding: 0cm 5.4pt;" valign="top" width="142">0.075 mg/kg body weight</td>
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<td style="width: 106.1pt; border-width: medium 1pt 1pt; border-style: none solid solid; border-color: -moz-use-text-color windowtext windowtext; padding: 0cm 5.4pt;" valign="top" width="106">Growing horses</td>
<td style="width: 5cm; border-width: medium 1pt 1pt medium; border-style: none solid solid none; border-color: -moz-use-text-color windowtext windowtext -moz-use-text-color; padding: 0cm 5.4pt;" valign="top" width="142">0.075 mg/kg body weight</td>
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</table>
<p><strong>Deficiency<br /></strong>Beriberi is the classical deficiency symptom of thiamin deficiency. Anorexia, bradycardia, muscle fasciculation and ataxia have been reported in horses with thiamin deficiency. Deficiency symptoms in horses fed typical feed ingredients have not been reported.</p>
<p><strong>Toxicity<br /></strong>As thiamin is a water-soluble vitamin, excess intake will be excreted in the urine. Thiamin toxicity in horses has never been reported.</p>
<p><strong>PC-Horse<br /></strong>PC-Horse calculates requirements for thiamin individually for each horse according to the NRC recommendations. It has also included values for thiamin (vitamin B<sub>1</sub> ) in all feed tables. When composing rations for your horse using PC-Horse, you will always be able to control that your horse’s thiamin intake is in accordance with its requirements (all versions except the Mini-version).</p>
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<p style="margin-top: 0.1pt; margin-right: 0cm; margin-bottom: 0.1pt;">&nbsp;</p>
<p style="margin-top: 0.1pt; margin-right: 0cm; margin-bottom: 0.1pt;"><em>This article was originally written by Dr. Day Austbø.</em><br /> <em>Copyright: PC-Horse International - Norway 2015</em><br /> <em>Feel free to use and publish the material. Please indicate the source and author.</em></p>