Eating straw?

Hi Guys
I have just come back from the allotment and the chooks, while I was in their run I noticed some long cylindrical poo about 5-10 cm. The poo seemed to contain strands of straw which would explain it being long and straight. Both the run and coop have straw in them and I have never seen the chooks eat the straw and this is the first time that I have seen this poo.

Has anyone experienced their chooks eating straw and is this ok and normal for them?