Set StartIndex for Zend getSubScriptionFeed from YouTube

Set StartIndex for Zend getSubScriptionFeed from YouTube

I want to set a StartIndex for a YouTube subscriptionfeed in Zend
Framework but I can't figure out how to do it. Tried both the
documentation on YouTube and Zend but couldn't find it. Even tried to look
through the Zend Framework PHP files but I didn't get much wiser. I can
get a subscriptionfeed using this code but I need to set a StartIndex as
well...
$yt = new Zend_Gdata_YouTube(getAuthSubHttpClient(), "", "",
YT_DEVELOPER_KEY);
$yt->setMajorProtocolVersion(2);
$subscriptionFeed = createYTObject()->getSubscriptionFeed($user);