I think the expression *blood, rain, or horse manure* is just a [hyperbole ][1] used in that specific circumstance to strongly convey the idea that he was going to run the miniseries at any cost. 



> - an extravagant statement or figure of speech not intended to be taken literally, as “to wait an eternity.”.


[Horse manure ][2] is used also metaphorically to indicate a nonsensical idea, but it is not related with the meaning used above. 

> - (euphemistic) if you describe something such as a statement or idea as horse manure, you are emphasizing that you think it is nonsense   ⇒ 'Sounds like horse manure to me, Mikey boy,' said Ballpark., It's all a load of old horse manure. (Collins) 

[Horse manure][3]: The Routledge Dictionary of Modern American Slang and Unconventional English.



  [1]: http://dictionary.reference.com/browse/hyperbole
  [2]: http://www.collinsdictionary.com/dictionary/english/horse-manure
  [3]: https://books.google.it/books?id=5F-YNZRv-VMC&pg=PA527&lpg=PA527&dq=horse%20manure%20american%20idiom&source=bl&ots=mjt0VxaD_q&sig=jyCKmexQP90HNTN9kQV_wuQ_lnU&hl=it&sa=X&ei=838CVeLtN4PfaM2RgvAC&ved=0CCwQ6AEwAw#v=onepage&q=horse%20manure%20american%20idiom&f=false