the meaning of "grass dogs (dogs of grass)" 天地不仁，以萬物為芻狗 that's Dao De Jing Chapter 5, 
I give a try: heaven and earth are not benevolent (I understand)
萬物 all the creatures 為 act  芻狗 grass dogs? dogs playing on grass? dogs made of grass?
What to you think?
is my translation of the second line in the right direction?
刍狗, is made of grass and used as sacrificial offering, metaphor for humble or useless things.

天地不仁，以万物为刍狗, means heaven and earth, i.e. the nature, is not benevolent and partial, it treats all things on the earth the same and fairly.

It just reflects the ideology of 道家(taoists); 顺其自然(let nature take its course, don't intervene too much).

http://baike.haosou.com/doc/6641911-6855725.html
http://baike.haosou.com/doc/5377628-5613764.html