If you want to know what the judges will be telling their family tonight after they leave the CDE, it will be that story. It's not the best example of personal responsibility, but there is enough emotion in the short story to make your point very persuasive.
Now, repeat the format of this paragraph for each of your points. Please don't hammer the judges with 3 or 4 gut wrenching stories, we may not recover. Mix it up, have one moving story like above, add a funny one for another point, a third where you did not do as told (by which you certainly learned your lesson), and one about working as a group and you had to get along to make things work. Make them just personal enough that we don't know the name of every family member that lives in your county and what kind of vehicle they drive. I speak from experience. If you have a particularly convincing point with a great example, save that one for last. The power of recency is that people tend to remember what we hear most recently and good points should be remembered.
Now that you convinced the judges of each of your three or four points, wrap it up with a conclusion paragraph. [Tell them what you just told them.]
The first sentence summarizes everything you just said. "As you can see livestock projects provide a world of experience and personal growth that teens can not achieve through a book"
The second sentence reminds us why these points were important. "While livestock projects are not always convenient for the family and sometimes can be more trouble than they are worth. The long term benefit far outlasts the short term complications to life."
The final sentence ties up the entire speech and should leave the judges with a smile. "Teachers, leaders, and peers can only tell us so many times about responsibility and personal growth. As we move towards adulthood we need many opportunities to succeed and fail so that we can grow as people and become responsible adults"
Do not introduce any new arguments, statistics, or stories in the conclusion. That's what the body of the speech is for. If you add those in the conclusion, the judges can tell you are buying time until the 4 minute mark and that you were not as well prepared and practiced as you should be. If performed correctly, what you have completed is that you just told a story of your life through an organized extemporaneous speech on a specific topic.
The more you practice, the more rhythm you will develop with your speech and the greater ability you will have to gauge time without a watch to look at. Practice does not make perfect, perfect practice makes perfect. You will fall short of first place not because the next FFA member has a natural born talent, but because they have practiced more, and more, and more, and more. You can do this.
If you need to mix things up in class, then take a look at our Public Speaking in the Classroom Lesson Plans. These lessons are a great way to incorporate public speaking into your Ag classroom. Click over and see how these activities will work in your classroom.