I can't find anyone to give me a straight answer on this. If I wanted to prove a bull was homozygous for a certain gene (for instance the black gene in an Angus bull), how many test crosses are required to prove such? Does anyone have a number?
Son of Butch":3dembz98 said:I don't know if there is a straight answer to 100% certainty.
It's possible 1 cross can prove a bull is not.
My estimate is 16 would put you in the range of 94% certainty and it would take many more to reach 99.4%
DNA test would tell you heterozygous or homozygous to 100% certainty and you would know much faster.
She was proven heterozygous black by having a red calf in her first 16 tries... so in her case it was enough.dun":3h9ohmmt said:I don;t know how many is required but I know 16 isn;t enough. Granny was a black Angus red carrier.
Bred to either a Polled Hereford, red Fleck or a Red Angus the first year she calved for us she had a red heifer.
The next 16 calves were all black.
The point was that even 16 may not mean anything. In her case 17 would have been enoughSon of Butch":35c80g22 said:She was proven heterozygous black by having a red calf in her first 16 tries... so in her case it was enough.dun":35c80g22 said:I don;t know how many is required but I know 16 isn;t enough. Granny was a black Angus red carrier.
Bred to either a Polled Hereford, red Fleck or a Red Angus the first year she calved for us she had a red heifer.
The next 16 calves were all black.
Just because her 17th calf was black doesn't mean the next 4 wouldn't all have been red.
Besides 93.75% (aka about 94%) is not 100%
16 crosses = 93.75% and 16 is the lowest number I would feel comfortable at calling him proven
20 = 95%
25 = 96%
30 = 96.666%
50 = 98%
To reach 99.4% certainty would take 167 crosses and yet there is still a minute chance the 168th calf would be red.
Without DNA testing you just have to pick the most reasonable number at which you feel comfortable.
Trivia:
97.37% probability of picking the wrong number on one spin of a Roulette Wheel
Correct for polled gene when both breeds are British. (any zebu blood screws everything up)CSM":3fzrnun6 said:In the case of homozygous polled, breeding to 10 horned cows and getting 10 polled calves, 99.9% accuracy.
Son of Butch":2nacdvsi said:I don't know if there is a straight answer to 100% certainty.
It's possible 1 cross can prove a bull is not.
My estimate is 16 would put you in the range of 94% certainty and it would take many more to reach 99.4%
DNA test would tell you heterozygous or homozygous to 100% certainty and you would know much faster.
ALACOWMAN":16954992 said:Has anyone noticed the double set of eyelashes on polled and homo..polled cattle, as opposed to single on the horned??
http://journals.plos.org/plosone/articl ... ne.0063512WalnutCrest":3ql0t5c2 said:ALACOWMAN":3ql0t5c2 said:Has anyone noticed the double set of eyelashes on polled and homo..polled cattle, as opposed to single on the horned??
I'm interested in your theories. Can I subscribe to your newsletter?
Had a better one while back,but couldn't find it again,,,,yet :cowboy:Son of Butch":341jf10h said:Interesting research, but Very Dry reading.