New Aggressive Behavior in Horse

Question
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Followup To
Question - Hi, Thank you for your quick response.  I feed Omolene 100, usually he gets 1 lb a day (he's a pleasure horse and easy keeper) and he's always been fed grass hay with a tasting of alfalfa thrown on top.  Right now he's down to a handful of grain a day and just grass hay.  He calls out to the mare at any time, not just when she's in heat.  She has a yearling with her, but not sure if that is relevant.  Our pasture is about 4 acres and we have a run-in shed/paddock on the property.  It's a 12' x 15' area for him (with a roof extending to 10'), and a 12' x 15' area for Red (we've separated them using boards and rectangular horse fence.)  Previous barns included either a stall with a run and no turn out (ridden 4X/week) or a stall with some turnout but no run.  He had very little interaction with any horses, however he was always able to see other horses.  My attention to him has increased because I now get to see him whenever I step out my backdoor as opposed to driving to see him once a day.  However, I have been giving attention to Red as well.  I have also been giving attention to the mare and yearling, but I'd say only 10 minutes out of my day, compared to probably 2-3 hours a day total with Silk and Red. Thanks again for your help!
Erin


Lisa

Answer
Hi Erin,
          From what you have told me I would say that during his 11 years in the herd that he was in he learn a certain herd dynamics and what his place was with them. When he was staying at the different barns he was unable to practice the herd dynamics and most likely began to think of himself as being the boss when it comes to other horses. When you moved him into your new place and got Red there were now only the two horses and as Silk feels himself to be the boss he picks on Red since Red does not fight back. You can do several things, one would be to borrow an Alpha horse from a friend who would put Silk in his place and teach him that he can not beat up on another horse, separate Red and Silk like you have or give Silk a supplement like Quite Mind which calms horses down. In regards to him whinnying at the mare it is not something to worry about. He either  just has a crush on her or prefers her and the yearling to Red. Unless he is injuring himself or her I would not worry about that.

Lisa