Bright Raven wrote:Angus Rocks ask:
1. why is everybody so concerned about getting this bull or that bull if they don't pass some good traits on?
Response: the bull contributes half the chromosomes. In cattle, there are 60 chromosomes. So his spermatozoa will contribute 30 chromosomes to the offspring. If he is a proven bull that has demonstrated that he carries dominant desirable traits, he will have a positive effect on the offspring.
that 30 chromosomes passed from each parent,.. that the statistical average right? Correct me if I'm wrong, but in some cases the split may be 20/40 (to get the 60 chromosomes) from one parent or the other.
This leads in to this statement
cow pollinater wrote:Most of the udder.... traits are around 15% heritable so the way you make improvement there is to breed
to the ideal with every mating. You might get lucky and get tons of improvement in one generation
If you breed to ideal long enough you will come out where you want to be.
Once in a while you'll get an animal that's a spitting image of one parent despite a very unique other parent.. If you're lucky, you get a calf that just got the best genes each parent had to offer, and you've made some steps forward
And that leads to hetero/homozygous traits, where sometimes you have great animals that have failures for offspring.. Just taking color as an example, a hetero black cow bred to a red bull.. despite the cow having the trait you want, there's only a 50% chance of the offspring being black, and when you do get a black calf from that mating, they will still only have a 50% chance of black calves when bred to red bulls.
Now if the bull is also hetero black, you might be able to make some progress to lock in that black trait.. Now the calf has a 75% chance of being black, but also has a 25% chance of ALWAYS making black calves even when bred to a red bull.. NOW you're making progress
If the bull is homo-black, your odds are 100% for a black calf, and a 50% chance any given calf will ALWAYS have black calves.. If you've identified an animal as homozygous for an important trait, and breed it to other animals that are homozygous for that same trait, you will never stray.
Real life of course is a little more complicated.. Perhaps you want "good udder" gene? but there are no black bulls with that, so you'll have to settle for a red bull that carries (and is homozygous for it preferably) the "good udder" gene.. In this case EVERY one of the first generation offspring will be black and have good udders, but since they are all heterozygous, their offspring will be a very mixed bag.. If you select and breed carefully, you can work yourself back to having both the homozygous black and homozygous "good udder", but it will take time and a lot of effort