I see you are a 45/70 fan from your sign in name. And I see you did not specify if you were partial to round balls or conical bullets. If you have any doubt load up some 240 grain, or heavier, slugs to get the job done. They still won't be akin to the 45/70 but more in line with the 44 Mag, which has a good reputation as a deer killer.
That said, on my very first year deer hunting nearly 30 years ago I was using my Dad's TC Hawkin and 45 Caliber conical bullets. The 1 1/2 year old buck stood broadside looking at this young man who took the opportunity to calmly put a hole through his chest. I was comfortable with the shot and all the hair on the ground confirmed a direct hit but with only 3 drops of blood to show for the effort, plus the fact this was my first tracking job on the first deer I had ever shot at, the day ended sadly. All day I searched everywhere I could look but never recovered that beautiful animal. I went to a .50 after that year, if only to assuage my conscience.
BTW, a 45 with conical slugs out of a crescent shaped stock can kick harder than a 50 slug out of a Renegade butt stock considerably. Your choice of stock design will make a difference.
I've been kicked by those motorized horses a couple times, too. Be persistent with your exercises and you can be shooting your big guns again, too.