Your lambs are huge at 140 to 160 lbs. What breed are they? Are they mostly Suffolks and Hamps? How long does it take to put that much weight on them? How old are they when they go to slaughter? How old are they when you buy them? What price do you pay to make it economical to feed them out? What exactly do you feed in an enclosed operation? I have never heard of this before, only in hogs.
For Fair lambs we aimed at 120-140 lbs. We were told that the processors' equipment couldn't handle lambs over 150 lbs. so the top weight was 140 lbs. Over 140 lbs. was a DQ for champion placement.
I have a very small Dorper ewe operation (smaller framed breed) and my lambs go to slaughter at 100 lbs. around 4-6 months depending on how much forage there is for them. My Dorpers actually gain faster and heavier on green forage instead of hay. This year our forage came late and my September October lambs were 6 month old with no creep feed. They weighed over 100 lbs. and graded Prime. Here my regular customers accustomed to buying supermarket lamb want 100 lb. lambs. Some ethnic buyers want 40 lbs., some 60 lb. lambs. If I have an ethnic buyer, I need to ask what weight they want. Mainly I like to raise to 100 lbs. by 4 months old and get them to slaughter.