In the first 5 books of the Bible, Moses describes the requirement of sacrificing a lamb "without defect" to remove sin. (Lev. 22; Num. 29) "Without defect" meant not blind, no broken bones, no skin defects, not lame, no blemishes, no cuts or bruises anywhere. (Lev. 22:21-24) The sacrifice was recurring and frequent. So, a lamb without defect was highly valued and protected. A newborn lamb was examined and if without defect, aggressively guarded.
A baby lamb can injure itself in the first hours of life by energetically reacting to changes in light, temperature, and moisture. Therefore, a lamb without defect would be wrapped in binding (swaddling) cloths and placed in a V-shaped feeding trough (manger) until accustomed to the new environment, so it wouldn't jump and bump around. Every shepherd and farmer knew that is how you care for, guard, and protect a highly valued sacrificial lamb.