The problem comes up when you get 3 maternal sisters in the herd say
1889, 2889,6889, plus third generation cows 0882,8886, and 0882's daughter 4880. Now suppose in 2009 four of these cows have good heifer calves. 9881, 9886, 9888,and 9884, no problem! until these 4 heifers calve, then you have 4 calves with the number 1889 plus the 10 year old cow
The rule is only one replacement heifer can carry the family number into the replacements per year, and I start looking for unused numbers and reasons for certain heifers to start their own branch of the family. (maybe 2 of the heifers are sired by a new A.I. sire I have high hopes for.)In the case above the 10 year old cow was a proven bull mother but had no other offspring in the herd so I changed her tag to 1669 and her heifer to 9661 and they became the "66 branch of the "88's". (66 looks kind of like 88) So the 2 heifers by the new bull become "9868 & 9444" (44 is half of 88) Doesn't mean any thing to anybody else but when I see 88's, 66's.44's,86's and 80's at least I know they all stem from that old Baldridge Oscar X PS Powerplay cow from Ericksons.
By the same "Aud" logic I know 3471,3578,3671,3730,4375' 5775,6370.7473,8473,8775,9473,9573 &9747 all go back to that first 137C heifer bred by Mick Cox in Nebraska. As a side note; around here anyway, there is no better way to give a young cow the " kiss of death" than to change her cow number and ask her to start her own cow family.

The 37's and 88's must have been really strong cows to have overcome that jinx. :lol:
My herd is small enough by the time a cow is 10, I know her well enough not to give her number to a heifer. I have never run this system on more than a hundred cows but I guess if you start with 300 to 500 cows you could change tag colors every 100 cows (x00-x99) and just go with 3 digits on the foundation cows.
At some point it just becomes too complicated and you loose any benefit or ability to be able to link cow families in the pasture at a glance. @[/img]