Friday, February 5, 2021

Where does “TYPE” fit into modern dairy selection and mating

 From the January / February Dairy Route Letter

My Dad began his AI career in 1952 with what became CURTiSS Breeding Service.   CURTiSS was   initially criticized for having no “proven” sires (offering the latest bulls from their own breeding herds) and for paying too much attention to “type”.      In spite of this, CURTiSS grew until it was the second-largest AI system in the USA  and accounted for half the annual growth of the entire AI industry.    Sons of leading CURTiSS sires found homes in every other AI stud.     Having “type” alongside production proved to be the winning formula that most “milk” studs had to adopt to compete.     Once everyone had this, CURTiSS’ owners refocused on Beef sires and lost its way.

What  was  the  impact  of  type  on  dairy  herds ?

Pretty simply, herd expansion from stanchion barns to free stalls proved that more uniformity in cow conformation was needed.     “Bad” type cows had udder failures, feet and leg failures, and were more susceptible to injury or calving difficulty.     Once out of the stanchion barn into free-stalls and walking to parlors for milking, type faults were more evident.    CURTiSS herds produced more milk because the cows were more durable, lasted longer, reaching the mature production levels that boosted herd averages.    A close affiliation with “aAa” Breeding Guide helped many dairymen to produce uniform cows that enabled transitions to larger herds.

How  does  “type”  relate  to  longevity ?

The clearest impact of “type” on longevity is not reflected in gaining a longer herdlife—it is in avoiding a “too short” herdlife, where a majority of culling is involuntary.     It takes a different definition of “type” to gain extended herdlife, a result of physically-balanced mating selection over depending on type indexes alone.      In this the goal is to have a higher percentage of the herd be cows of mature age, producing at their peak production capability.

Where  is  the  AI  market   going ?

As busy dairymen, we tend to seek simpler answers to important questions like “which bulls should I use?”     Thus the answer “use the bull ranked #1” has always had its attraction.    This was an expected result of geneticists’ pursuit of various “single trait” selection methods, which believed the fiction that the ideal genotype could be “fixed in place” by having all homozygous gene pairs for the production traits.     However, one system after another failed to deliver after the three generations of “hybrid vigor” was used up.     There is no escaping that all mammals are conceived from two genotypes that each provide half their genes into the new individual.   From that point on, the physique produced by that mating must adapt to the real environment rather than to a theoretical “ideal” in which all impediments to success have been solved.

Genomics is the latest and greatest “single trait” selection idea, defining an ideal genotype for males and then duplicating it for their female mates.     We no longer wait for elite pedigrees to grow up to be evaluated for “type” (or tested for “milk”) – we just assume they are the best as offspring of other elites.     Might still be good insurance to add in “aAa” to Genomic selection.  

How  to  make  “type”  have  an  impact  on  “longevity”

Here are two examples, from International Protein Sires and the other from Triple Hil Sires.   In both cases, what is evident is a “deep” (multiple generation) maternal line in which cows reach maturity and have their best lactations then while also reproducing their uniqueness into a next generation.    One of your clues to this is the “EX-92 3E” sort of designations, which tells you the cow has peak physical functionality over an extended productive life (3E means cow was still in good enough shape to rescore “Excellent” three times after her initial EX lactation, with added calving between each rescore).      How often do you see this in a competing AI stud bull book?

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