And you shall eat before Hashem your God, in the place that He will choose to make His Name dwell there, the tithe of your grain, of your wine and of your oil, and the firstborn of your herd and of your flock, in order that you may learn to fear Hashem your God all the days.
English: "Tithe and firstborn" — It was taught: Others say: "Tithe and firstborn" — he compared the firstborn to the tithe; just as the tithe is not disqualified from one year to another, so the firstborn is not disqualified from one year to another.
On the daf / in context: A firstborn remains valid for consumption within its first year even if the year boundary is crossed, by analogy with the rules of ma’aser.
Type of Learning
Hekkesh (Temurah) — the firstborn is not disqualified by the passage of the year boundary.
What Is Learned
A firstborn animal is not disqualified merely because the year in which it was born has ended.