I also find it hard to believe that Oro/Kabuto didn't have some DNA of Jiraiya somewhere. For crying out loud, he had the DNA of guys from an older generation (Hashi/Tobi/Mada) -- especially since getting Madara's DNA would seem damn near impossible considering Obito is the only one who knew his status and whereabouts. He even had the DNA of some of the greatest warriors in the world. How are you going to tell me he didn't have Jiraiya's DNA? Perhaps Oro has a weak spot for Jiraiya and didn't want to take the DNA of his best friend.