So, When Does a Lamb Become a Sheep?

Most of us already know that among domestic animals, the babies and adolescents have special names. Pigs have piglets. Cows have calves and sheep, of course, have lambs.

Hardly special knowledge but the trick is determining when these babies are officially considered adults. We’ve already discussed the differences between lambs and sheep, but when does a lamb actually become a sheep?

In most countries, a lamb is considered a sheep when it’s 12 months old, despite all other physical indicators of maturity. Depending on the context, a sheep might still be considered a lamb after this time, however.

This is one of those instances in animal husbandry where the lingo can truly get confusing, or even downright bewildering!

Sometimes, lamb is considered sheep based on age alone, but other times, physical characteristics do play a part.

Of course, this is all filtered through geographical and cultural lenses, too, with different countries and cultures having different standards. I’ll explain all this and a lot more below…

Is a Lamb Considered a Sheep when it is Physically Developed?

No, not typically. Much of the time, an animal is considered an adult when it is fully grown and developed physically.

This is not really the case with lambs, which are still considered to be so even when showing all the physical signs of maturity.

Depending on the breed and the individual animal, a lamb might be physically mature and as little as 6 months and it rarely takes longer than a full year.

Despite this, in most areas a lamb is not considered a lamb until it is one year old.

Is a Lamb a Sheep When It Starts Eating Solid Food?

No. Depending on the objectives for the lamb and other factors, a lamb will usually suckle its mother’s milk for at least 3 months at which point it is typically weaned.

Upon being weaned, the lamb will start eating grass and other foods that adult sheep eat.

However, it is possible that a lamb might be fed milk for a time after this point.

Once again, despite weaning and transitioning to a diet of solid food a lamb is still a lamb until it is one year old, at least in the United States and the UK.

Does a Lamb Become a Sheep When it’s Sexually Mature?

No, it doesn’t. Sheep can sexually mature quite quickly, surprisingly quickly in fact. And once again despite this, they are still considered lambs.

But there’s a difference between rams and female sheep when it comes to sexual maturity.

A ram might be sexually mature and ready to reproduce as young as 3 months old, if you can believe that, and females are only right behind them at between 5 and 6 months old.

So even though a lamb is ready to mate like an adult, and pass on its genes like an adult, it isn’t considered an adult and is not called a sheep except generically.

Is There Any Biological Change That Signifies When a Lamb Becomes a Sheep?

No, except in a few rare cases when referring to sheep meat sold at market in the UK and other countries, and specifically that taken from young lambs.

As described above, by all outward appearances a sheep might be fully mature in its first year of life and still be categorized as a lamb.

However, when referring to the sale of lamb meat, which as a general rule of thumb is taken from any sheep that is younger than one year of age, and mutton, taken from sheep that is older than one year there might be some qualifiers in the UK, Australia and New Zealand.

In Australia, lamb is a definition given to any sheep that doesn’t have any permanent incisor teeth “in wear,” meaning extending past the milk teeth.

The same applies in New Zealand, but Great Britain defies lamb as having no permanent incisor teeth at all.

So, in some cases, a lamb might be slightly older than one year and still fit the legal definition of land in these countries.

When Do Other Countries and Cultures Say Lambs Become Sheep?

Again, as a rule of thumb, upon reaching one year of age though we’ve already learned there are a few exceptions according to the previous section.

And here’s another one: In Australia, the UK and New Zealand, sheep meat that is sold in grocery stores that is less than 2 years old may legally be called lamb outside any other specifications.

Talk about confusing! We’ll talk more about marketing regulations for lamb meat and other products in just a bit.

Are There Any Regulations or Laws that Specify When Lambs Become Sheep?

Yes. Further complicating matters, government agencies responsible for agriculture and consumer safety might have their own conventions and grading systems for classifying lambs.

For instance, the USDA only partly assigns lamb status to an animal based on its age.

So once again, it is possible for a sheep to be legally considered a lamb when it is sold and slaughtered depending on a variety of factors.

Is a Lamb Still a Lamb Even When Fully Grown?

Potentially, yes. And this is an occurrence that happens quite regularly.

As described above, a sheep might be fully grown and physically mature in all aspects well before a year is out and still be considered a lamb. In short, they are adults in everything but name at this point.

However, in some other countries as discussed above, it is possible for a lamb to be older than a year and still considered a lamb due to the eccentricities of permanent tooth development.

If you are thinking this does not make the positive identification of lamb and lamb products on the market easy, you are quite right. It is bordering on smoke and mirrors at this point, I think.

Does the Lamb Designation Change How Sheep Products are Marketed?

Yes, definitely. As I just alluded to it can be very difficult the positively determine what is and isn’t lamb when purchasing products and specifically meet.

By way of a for instance, in the United States lamb meat can potentially be any lamb that was slaughtered at up to 20 months of age- and will still meet the government-mandated definition of Prime-grade lamb!

And worse yet, Choice-grade lamb is still called lamb and it can be a sheep of any age!

In other countries, “spring lamb” has a very specific definition referring to a young lamb that is born late in the winter or in very early spring and slaughtered while it is still on a diet of milk.

In the United States, this term simply means any lamb that was slaughtered between March and October – virtually meaningless!

But things get even more confusing in other countries and even in some specialty butcher shops in the United States.

“Yearling lamb” is a common term, but one that refers to any sheep between the ages of 12 and 24 months old. Once again, we see the “less than one year old” convention utterly ignored.

Another term that gets confusing is “young lamb.” This term refers to any purely milk-fed lamb that is between one-and-a-half and two months old. Strangely specific, considering all lambs are generically less than a year old.

In short, if you don’t know, you yourself, precisely where your lamb meat came from and when it was butchered, you might be eating mature sheep or you might not.