According to the Spanish food site Directo al Paladar, a cordero lechal is a lamb that has been slaughtered at around one month old. It weighs around 13 pounds (6 kilograms) and has consumed nothing but ewe's milk .
Cordero lechal is prized in Spain because it is delicate in flavor and has none of the "gamey" taste of older lamb or mutton. Cordero lechal is also low in fat and very tender. In the picture above (credit to the article "Lechazo asado" from Wikipedia en español), you can see in the foreground uncooked sides of cordero lechal. Notice the light color of the meat. This light color is also typical of cordero lechal.
As I mentioned in yesterday's post on grilled lamb chops, whole roasted baby lamb, cordero lechal asado, is traditionally served on Christmas Eve in Spain, but it may also be served on any special occasion.
In Spain there is also cordero recental, lamb slaughtered at around 30 pounds (15 kilos). Cordero recental has consumed grass and feed as well as milk. It has a stronger flavor, higher fat content, and slightly darker meat, but it is still mild, low in fat, and tender by U.S. lamb standards.
Cordero pascual is lamb slaughtered between 4 to 12 months of age. Cordero pascual has red meat, high fat content, and a pronounced "lamb" taste.
Almost all of the lamb available in the U.S. would be classified as cordero pascual in Spain. Because there is such a big difference between cordero lechal and cordero pascual, one can't really substitute for the other.
Back to José's question: is there a source for cordero lechal here in the U.S.?
To my knowledge, no.
According to Wikipedia's article on lamb and mutton, milk-fed lamb is almost never available in the U.S. or the U.K. It is considered to be uneconomical. I have searched for cordero lechal with no luck.
I suspect it would be necessary to go directly to someone who raises lamb to obtain cordero lechal here in the U.S. Baby goat, cabrito, may be easier to find. It's probably the best substitute.
I will keep searching. If anyone knows a source in the U.S.A. for cordero lechal, please let us know.
Until then, cordero lechal asado is yet another reason to visit Spain.