open mouth breathing

Question
Hi and thank you in advance for taking the time to read my question.

I own a rescue rabbit, literally rescued from the hands of some teens. I'm not sure what type he is (but you can see him in the video below).  

He must have been 6 months when i got him so that would make him about 6 1/2 now. His name is Pipkin, or Pip for short :)

He's been in great health, never needed a vet besides orig. checkup and neutering. Lately, as in the last 3-4 weeks, i noticed he 'hacks' or 'coughs' when eating his Timothy hay. Just one or two per eating session.

Also, when he breathes now, his body 'moves' along with his breathing much more - before only his stomach / diaphram would move, now his body and his head moves quite a bit while breathing.

I researched online, and read that open mouth breathing was not a good sign. I videotaped Pip and tried to get a closeup of his open mouth breathing (i turn the light on at the end).  

Overall, his energy level is down a bit from years ago but not 'suddenly'. He will still bink when out and about.

Im wondering if I should worry, or if ol Pip is just getting old....

Thank you,
Jared

https://www.youtube.com/watch?v=6nGvoYet528

Answer
Hi Jared ,
I couldn't open the video it was 'private'..is he a miniature breed? lop? dwarf?
 The smaller breeds tend to live a lifespan of approx 6-8 years,,some can reach older,but that's the approximate age. The breathing sounds like it could be an allergy from the hay,as it is dusty and can irritate the respiratory passages. try misting his hay   before feeding it to him in his cage to remove and foreign dusty particles,this might be the cause. if not,I would imagine it could be related to his age,,try to resend me the video,would help :)
best regards,