How to call OnChange when form opens

My code works except for when it opens, it does not display what is in the dropdown. When you select a value in the dropdown, it works perfectly. I want it to open with the table hidden and then when changed to something else have it display as it does. Could a call to onchange when the form opens work?

My code:

<table width="522" border="0" text-align="center">   
    <tr>
        <td width="124">Number of animals:</td>
        <td width="129"> 
           <select name="count" select id= "count" onchange="showRows(this)">
              <option value="00">00</option>
              <option value="01">01</option>
              <option value="02">02</option>
              <option value="03">03</option>
              <option value="04">04</option>
              <option value="05">05</option>
              <option value="06">06</option>
            </select>
        </td>
    </tr>
</table>
<table width="404" border="0" align="left" cellpadding="0" cellspacing="0" id="mytab" >
    <tr class="tabletitle">
        <td width="16" class="invisible">00</td>
        <td width="16" align="right" class="tabletitle">#</td>
        <td width="73" align="center" class="tabletitle">Gender</td>
        <td width="60" align="center" class="tabletitle">ID Number</td>
        <td width="281" align="center" class="tabletitle">Name</td>
    </tr>
    <tr class="light" id=>
        <td align="right" class="invisible">01</td>
        <td align="right" class="count">1</td>
        <td class="white">
            <select name="gender1">
                <option value="Select" selected="selected">Select</option> 
                <option value="Male">Male</option>
                <option value="Female">Female</option>
            </select>
        </td>
        <td class="white"><input name="id_number1" type="text" id="id_number1" size="10" ></td>
        <td class="white"><input name="name1" type="text" id="name1" size="35" ></td>
    </tr>

    <tr class="light">
        <td align="right" class="invisible">02</td>
        <td align="right" class="count">2</td>
        <td class="white">
            <select name="gender2">
                <option value="Select" selected="selected">Select</option> 
                <option value="Male">Male</option>
                <option value="Female">Female</option>
            </select>
        </td>
        <td class="white">
          <input name="id_number2" type="text" id="id_number2" size="10" >
        </td>
        <td class="white"><input name="name2" type="text" id="name2" size="35" ></td>
    </tr>

<tr class="light">
    <td align="right" class="invisible">03</td>
    <td align="right" class="count">3</td>
    <td class="white"><select name="gender3">
        <option value="Select" selected="selected">Select</option> 
        <option value="Male">Male</option>
        <option value="Female">Female</option>
    </select></td>
    <td class="white"><input name="id_number3" type="text" id="id_number3" size="10" ></td>
    <td class="white"><input name="name3" type="text" id="name3" size="35" ></td>
</tr>

<tr class="light">
    <td align="right" class="invisible">04</td>
    <td align="right" class="count">4</td>
    <td class="white"><select name="gender4">
        <option value="Select" selected="selected">Select</option> 
        <option value="Male">Male</option>
        <option value="Female">Female</option>
    </select></td>
        <td class="white"><input name="id_number4" type="text" id="id_number4" size="10" ></td>
        <td class="white"><input name="name4" type="text" id="name4" size="35" ></td>
</tr>

<tr class="light">
<td align="right" class="invisible"0>05</td>
<td align="right" class="count">5</td>
<td class="white"><select name="gender5">
<option value="Select" selected="selected">Select</option> 
<option value="Male">Male</option>
<option value="Female">Female</option>
</select></td>
<td class="white"><input name="id_number5" type="text" id="id_number5" size="10" ></td>
<td class="white"><input name="name5" type="text" id="name5" size="35" ></td>
</tr>

<tr class="light">
<td align="right" class="invisible">06</td>
<td align="right" class="count">6</td>
<td class="white"><select name="gender6">
<option value="Select" selected="selected">Select</option> 
<option value="Male">Male</option>
<option value="Female">Female</option>
</select></td>
<td class="white"><input name="id_number6" type="text" id="id_number6" size="10" ></td>
<td class="white"><input name="nam6e" type="text" id="name6" size="35" ></td>
</tr>


</table>

CSS:

.white { 
    font-family:arial;
    padding:5px;
}

.tabletitle {
    font-family:arial;
    padding:5px;
}

.invisible {
    color:white;
}
.count {
    font-family:arial;
    color:#999;
    padding:5px;

}

Javascript:

function showRows(s){
    var t=s.options[s.selectedIndex].text;
    var rows=document.getElementById('mytab').getElementsByTagName('tr'), i=0, r, c;
    while(r=rows[i++]){
        if(t=='12'){
            r.style.display=''
        } else{
            c=r.getElementsByTagName('td')[0].firstChild.nodeValue;
            r.style.display=c<=t?'':'none';
        }
    }
}