Why url ends with ?_={timestamp} in load js script request?

In view I wrote:

<script type="text/javascript" src="@Url.Content("~/Scripts/cm/customfield.scripting-helper.js")"></script>

But in Chrome Developer Console, tab Network I see this:

.../Scripts/cm/customfield.scripting-helper.js?_=1458129402165

How can I programmatically remove this substring? Or prevent it?