Feeds are the growing trends now a days and everybody wants subscribers to come to their site due to many reasons like increase Alexa etc.
If you see feed burner feeds emailed to you they are set to show as full post in the email that lets reader to read all the stuff there but if you want the reader to come back again you need to add a read more button there.
To do this, follow the instructions:
Go to blogger account
Go to settings
Go to other option
“Allow blog feed” will be set to full by default, change it to “until jump break”
Then where ever you will put the jump break it show only the part above that break.
By the way this is jump break while editing a new post.