Explaining Inbreeding Coefficients (IC )

Wright's Coefficient of Inbreeding states the probability that an allele (such as blue eyes for the eye color gene) will be the exact same gene (inherited from the same ancestor), on both an individual's chromosomes, as we get one diploid (or matching chromosome) chromosome from each parent, for our 46 chromosomes (23 from each parent). More simply stated, it is the probability that an animal with two identical genes received both genes from one ancestor.

For cows, they have 60 chromosomes, or thirty from each parent. Clearly the more inbred you are, the greater the chance is that you will get the same gene from both parents who share a common ancestor. And, the higher the inbreeding number will be. So high numbers are not good.

Take a first-cousin mating. First cousins share a set of grandparents. For any particular gene in the male, the chance that his female first cousin inherited the same gene from the same source is 1/8. Further, for any gene the man passes to his child, the chance is 1/8 that the woman has the same gene and ½ that she transmits that gene to the child so 1/8 X ½ = 1/16. Thus, a first-cousin marriage has a coefficient of inbreeding F =1/16.

EPD s vs EBVs

An Estimated Progeny Difference (EPDs) is the prediction of the genetic merit which an animal transmits on to its progeny. Estimated Breeding Values (EBVs) are based on the animals own performance plus the performance of all known relatives: sire, dam, half sisters, etc. An animal’s breeding value is its genetic merit, half of which will be passed onto its progeny. Since calves receive half their genes from each parent, an EPD = ½ EBV.

Understanding EBVs
EBVs report the breeding value of a variety of performance traits – from birth weight to mature cow weight, eye muscle area to IMF%. The critical point here is that the value of any given performance trait is determined by comparing it to those of other animals in the herd: particular animals are valued as being either above or below the herd average (or 50%) - in the case of the GROUP BREEDPLAN, the animals are valued as being either above or below the Wagyu Breed average.

EBV Traits Commonly Used

  • Birth Weight is based on the measured birth weight of progeny, adjusted for dam age: the lower the value, the lighter the calf at birth
  • 200-day Growth is calculated from the weight of progeny taken between 80 and 300 days of age, adjusted to 200 days and for dam age
  • 400-day Growth is calculated from the weight of progeny taken between 301 and 500 days of age, adjusted to 400 days and for dam age
  • 600-day Weight is calculated from the weight of progeny taken between 501 and 900 days of age, adjusted to 600 days and for dam age
  • Milk estimates milking ability: for sires, it indicates daughter’s milking ability as inherited from the sire
  • REA is calculated from live animal ultrasound scans at the 12/13th rib site, adjusted to 500 days of age: the higher the value, the larger the eye muscle area, and the better muscled and higher percentage yielding progeny will be produced
  • Intramuscular Fat % estimates the genetic difference in percentage of scanned IMF at the 12/13th rib site in a 500 day animal: the larger the percentage, the better.

    NOTE : The IMF% EBV should not be confused with Marbling – without actual carcass data this EBV only serves to point in the direction of expected value. A direct correlation has not yet been proven.

We are currently gathering the following data for submission to the AWA.
Please look for these statistics in our livestock reports.