The_excerpt_rss

Hi, how i can use exceprt in rss?

i’m trying with this code :

<?php // Get RSS Feed(s)
include_once(ABSPATH . WPINC . '/feed.php');

// Get a SimplePie feed object from the specified feed source.
$rss = fetch_feed('http://my_rss');

// Figure out how many total items there are, but limit it to 5.
$maxitems = $rss->get_item_quantity(5); 

// Build an array of all the items, starting with element 0 (first element).
$rss_items = $rss->get_items(0, $maxitems); 

?>

<ul>
    <?php if ($maxitems == 0) echo '<li>No items.</li>';
    else
    // Loop through each feed item and display each item as a hyperlink.
    foreach ( $rss_items as $item ) : ?>
    <li>
        <a href='<?php echo $item->get_permalink(); ?>'
        title='<?php echo 'Posted '.$item->get_date('j F Y | g:i a'); ?>'>
        <?php echo $item->get_title(); ?></a>
         <?php echo the_excerpt_rss( $cut, $encode_html ); ?>
    </li>
    <?php endforeach; ?>
</ul>

but the excerpt show content from last post listed in a page e not from feed.
Thanks.