What Makes EPDs Unreliable in Young Animals?

Jared Decker (University of Missouri): EPDs are unreliable for young animals because every generation when we produce a new calf we have random sampling of chromosomes and genes. So, chromosomes are just the string of DNA on which genes are inherited. So, when a bull produces sperm, that sperm gets a random sample of his chromosomes. So, every animal carries two copies of each chromosome, one inherited from the father and one inherited from the mother. When that bull produces that sperm cell, we get a random sample of his maternal and paternal chromosomes. There are billions of combinations of these maternal and paternal chromosomes, so we see lots of variation between full siblings. So, when we mate a bull and a cow and produce a large set of full siblings, the amount of variation that we would expect to see between those full siblings is actually equal to half of the variation that we would expect to see in the entire population.