Do you focus on linear trait information?

  CONCEPTIONS    Dairy route newsletter                  Nov-Dec 2023 

There seems to be three major ways most dairymen pick out sires.
  
Those who generally let the AI stud control their breeding choices are getting cows randomly bred to Genomic index selected young sires.    Those who like to pick their own mating sires generally base selections on linear trait data, pedigree/maternal cow line data, “aAa” breeding guide  (DMS is a derivative of early “aAa”)  or some combination of those three. 

A major reason many dairymen still only use progeny evaluated sires is a general mistrust of a selection method that is based totally on drawing eggs from pre-pubescent heifers and mixing semen massaged from equally young bulls, creating an embryo in a lab in a Petrie dish.    There is this recurrent theory of “accelerating generations” to create bulls two or three generations “newer” than any current “proven” (progeny evaluated and verified) sire.    Thus the data sets on such bulls are all imputed from their possession of desired “marker genes” in their DNA.

So does linear data come from “real” cows, compared to their dams?    NOPE.    Never was and never will be.    Again, the genetic theory is to find the best performers in the current generation of sires; therefore, linear is a comparison of “contemporaries” (when we had daughter proofs, it meant bull x compared to unrelated heifers in same herd same age).   There is NO biological link in this information to say that when a cow got bred to this bull, the following trait deviations are found between his daughters and their dams.    Now that we have Genomic linear estimations, it is primarily a combination of “parent average” trait deviations and gene markers associated to each linear trait (in some cases, only one or two genes involved).     The heritabilities of all this linear information, as a result, are often too low to be seen in your herd.