get_the_content_feed( string $feed_type = null )

function get_the_content_feed($feed_type = null) {
	if ( !$feed_type )
		$feed_type = get_default_feed();

	/** This filter is documented in wp-includes/post-template.php */
	$content = apply_filters( 'the_content', get_the_content() );
	$content = str_replace(']]>', ']]>', $content);
	/**
	 * Filters the post content for use in feeds.
	 *
	 * @since WP-2.9.0
	 *
	 * @param string $content   The current post content.
	 * @param string $feed_type Type of feed. Possible values include 'rss2', 'atom'.
	 *                          Default 'rss2'.
	 */
	return apply_filters( 'the_content_feed', $content, $feed_type );
}