Sample problem?

Soooo I recently made a beat and i used a sample at the beginning sequence. When i export it to mp3, the sample gets cut short...... i was wondering if anybody could help me fix this??

Funny I had this with a song I made and wanted to put under a video, the first second or so were gone... Didn't solved it...made me flip out big....ended just doing a fade in... Had that only one time probably the time I exported it to an MP3 file l, now I just use the wav file