What is the Ideal Weight for a Market Lamb?

Over the years, I’ve read many articles about the ideal weight for market lambs and had  many conversations with producers.  I am left with the impression that many domestic lambs are grown to well over 100 pounds, to 110 and 120 or even to more than 130 pounds. I have long wondered why. Why make lambs this heavy?

As many of you have gathered by now, I am coming from the old world; from Germany, to be precise. My first 11 years of a total of 29 in the sheep business were spent “over there”. Naturally, when I came here I did many things the way I did in the old country, one of them being that I harvest my lambs at 80 to 90 pounds live weight. However, most of these lambs were at first sold at the local sales barn and I didn’t give the weight much thought from a marketing perspective, only from a production perspective. A few were sold directly to individual customers. While I had mostly positive feedback, I distinctly remembered a customer complaining about the size (or lack thereof) of the leg of lamb. She stated that the ones she previously purchased at the supermarket were much larger. I suggested that this is where she ought to get her lamb from here on, figuring the leg of lamb was compared to a large grain-fed Suffolk lamb (or something like that), with which I wasn’t going to compete.

Seven years ago I moved to the Fingerlakes area and had to look for new customers. Two of the new ones were food vendors who purchased my lambs and sold it in places like New York City to restaurants and stores. To my surprise at that time, the weight was discussed quite extensively. They wanted heavier carcasses. I wanted to stick to my guns. So I started thinking a little more about why I did what I did and why I wanted to stick with “my” weight and not theirs.

Let’s crunch a few numbers first so that we are all on the same page. When a lamb is harvested, the carcass weight is about 50 percent of the live weight. That figure can vary a little. Lambs of wool sheep breeds when carrying some wool will often “dress out” a little less than 50 percent. Hair sheep breeds tend to dress out a little above 50 percent. Then, you need to take into consideration  the amount of food the lamb still had in its guts at the time of harvest because that affects that percentage as well. On top of it, in some slaughtering facilities the carcass is weighted with the head on and in some without. So let’s not complicate the issue and for easy math let’s settle for 50 percent of a live weight being the carcass or dress weight.

I have medium sized sheep. The ewes will reach about 160 to 180 pounds when fully grown. Individual animals may weigh a little more but I do not have sheep that weigh above 200 pounds when fully grown. However, many sheep breeds in the US do get that heavy. A large sheep has higher maintenance than a medium sized sheep. Yet, a large sheep cannot give you more lambs either.

Furthermore, higher maintenance most often requires feeding grain, something I don’t do. Naturally, a medium sized sheep cannot have a lamb as large as a large sheep. Secondly, a lamb grows with relative ease and speed, if fed appropriately, to 80 pounds and slightly above. I reach that weight on average between 4 and 5 month with my male market lambs. The top lambs get to 80 pounds at three and a half months. These are mostly single male lambs from adult ewes. Some lambs will need 6 or perhaps even 7 months to get to this weight. These are often lambs that were born to a young ewe, perhaps even a twin born to a ewe that lambed the first time that doesn’t get the same milk as others and therefore grows slower.

At about 80 to 90 pounds I have a lamb that is exactly as it should be: the bone, meat, and fat ratio is exactly right. The lamb is meaty and it is ‘finished’ – meaning it has just the right fat cover. Fast growing animals put a bit more growth into meat a while longer. So they might be finished at 90 lbs. or slightly above. However, once the lamb reaches a weight well above 90 pounds and starts reaching 100 pounds, that ratio starts changing. The lamb now starts putting more nutrients into producing fat and less into muscle growth. They also grow slower. So while I need to have more input for the same growth, I also have the input turned into more fat. You are not getting bonus points or premium prices for more fat last time I checked. So it makes sense to sell these lambs at this point, which amounts to about 40 to 45 lbs. dress weight with some lambs just under 40 lbs. and some in the high 40s or even 50 lbs.

I always figured that this is a rather selfish approach, viewing the issue from only my end, the production end. Then I read a research report by Whit C. Stewart in “The Shepherd” magazine that addressed this issue. According to the author only six percent of the graded carcasses in the US were 45 to 55 lbs, yet these ‘light’ carcasses retrieved the premium. The author gleaned the data from a USDA weekly report. He goes on listing the norm for carcass weights in New Zealand and Australia, being 35 to 44 lbs. and 39 lbs. to 52 lbs. respectively.

When it comes to sheep, I am always listening to what they do down under. The sheep production in these two countries are the leading edge in the sheep industry. It so happens to be the case that their approach and mine are matching. In case of my vendors I went to rather great length explaining why I didn’t want to increase the weight before harvesting. Perhaps in the future I only need to use one sentence: “For my medium-sized sheep, 40 pounds dress weight makes the ideal lamb carcass.”