Another old one. 

Luke's mule 

"say thar, Luke. I heered you been try'n to save money by 
gittin free sawdust down at the mill ter feed your mule. 
Are ye hav'n good luck wid that? 

"Naw, they didn't work out lek it shoulda, me be'n scientific 
'n all. I started mix'n sawdust with oats a bit more at a time. 
Finally he twer etn nearly the hole pail of dust, when he up 
and died."