When you say herd are trying to introduce the horse to the herd, or is it having trouble in the herd. Every herd dynamic is different and it depends on how strong your herd leader is and the personality of the horse your introducing. If the new horse is the dominant type and likely to challenge the others then it may take longer then a more submissive personality, that just goes to the bottom of the hierarchy.
When I get a new horse I keep it separate from my other horses for at least two weeks, they get to see each other across the fences, but no touching. Then I will put the new horse out with my lowest horse in the pecking order, and depending on how things go I introduce a another horse every couple days. I go up the pecking order, by the time my alpha gets introduced the new horse has had time to find its place in the pecking order and depending on where he is in the pecking order determines if he challenges the alpha or not. But if he does the others already know to stay out of it. I have certain combinations of horses that work and some that don't. The ones who are constantly fighting and beating each other up don't go out together. Hope this helps.
I was typing while you added more information. But putting a lone horse into an established herd is very hard for them to find a place. If you can find a way to separate her and add horses to her area, then out together she is more likely to become part of a herd. She was overwhelmed and scared being put out with so many horses and as you saw the alpha went right over and gave her the business. Think of high school clicks and how mean they can be to outsiders when they are together, but get the individuals apart and they are nicer.
Last edited by gssw5; 08-13-2013 at 08:21 PM.
Reason: Additional information