this year's (animal/plant); born this year; year of birth
Primarily used in agricultural, livestock, or horticultural contexts to refer to an animal or plant born or planted in the current year. Also used adverbially to mean 'this year' in formal or record-keeping language.
This year's calf is still small.
当歳の苗木を植えた。
I planted this year's saplings.
yearling; one-year-old colt
Compound of 当 (current, this) and 歳 (year, age). The exact historical derivation is uncertain, but the term is conventionally used in agricultural and record-keeping contexts.