If the calf is a heifer that we plan to keep as a herd cow, she'll get a new number when we Bangs vaccinate. (That's brucellosis, for those who aren't familiar. The vaccination is required if the cow is ever to be sold). The first digit of the heifer number is the year she was born. So a 2014 heifer has a 4 plus her mother's root number. Example: Cow 7587 (born in 2007) had a heifer calf last year.
The original calf tag in the left ear is the same as Mom's, 7587, but the daughter gets a second, permanent tag in the right ear with the number 4587. This tells us this new cow was born in 2014 and her mother was 7587, whose breeding history we know. This is important because the decision of whether to keep or sell a heifer sometimes comes down to her mother's productivity and personality. Was she a consistently early calver who never had trouble giving birth? Did she have a lot of milk? Take good care of her calf? Try to stomp us into the frozen ground when we applied the eartag in question? Is she a fence crawler who's constantly out in the neighbor's grain field and took her sweet, impressionable daughter along?
Obviously, the numbering system has limitations. There's only room on the tag for four digits if they're going to be large enough to read from a dozen yards away, out in the pasture. So if cow 7587 had a heifer calf last year and another this year, they would be 4587 and 5587, which is fine. But when 5587 has a calf in 2017 and it's a heifer, it'll be...7587. Assuming Grandma's still around, we have problem. And if 5587 and 4587 both have heifer calves in 2018, if we stuck to the system they'd both be 8587. That's when we have to assign a new number to the third generation and rely on our record-keeping to track her lineage. But since our books are in impeccable order...(cue uproarious laughter from anyone who's ever met us.)
Overall, though, the system works pretty well. Especially when it comes to good ol' 0001, who has a rather unique personality that she seems to pass on to her daughters and granddaughters almost without fail. And it's always good to know that the minute their calf hits the ground, these otherwise docile creatures are going to morph into The Pawing Cow.
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