I want to let everyone know If you follow Jacks book On Fertility on the stud dog . I have to say i used it on a stud dog that i didn't know the age of but had to of been at least 10yrs or 12 yrs human life and i followed his guideline as directed. And i was successful with getting His final litter but due to me taking him off and slacking up on a Major breeding I was unsuccessful the second time. His book and instructions are very simple if you don't understand just reread it a couple of times before you start doing something that you don't understand. I like all have all jack Publications and DVDs i have slacked being lazy and when i sit down and research his books and the books he inform you that should be in your arsenal Please GET! im in the process of Acquiring them all WHY??? More knowledge more access to solutions to your problems