Why do the Genomic AI studs not practice what they have preached?

 

Challenging the popular viewpoints on computer matings to avoid pedigree inbreeding

During the dynamic years of building high production dairy herds utilizing the higher ranking of high reliability evaluation of progeny across a diversity of herd environments, a small handful of 1960s sires came to dominate each breed.    Most notably, in Ayrshires it was Selwood Betty’s Commander:  in Brown Swiss it was Welcome In Stretch:  in Jerseys it was Observer Chocolate Soldier  (often in combination with his half brother, SS Quicksilver of Fallneva):  in Guernseys it was Maurana Wis Telestar:  finally, in Holsteins it was that duo of  Round Oak R. A. Elevation crossed with Pawnee Farm Arlinda Chief.    (Many thought Carlin M Ivanhoe Bell as a leader in protein yields would eclipse them, but thanks to the “BLAD” and “CVM” recessives showing up as he was linebred against other “Ivanhoe” descendants, his pedigree influence waned.)

What these sires had in common was an ability to produce offspring that transitioned dairying from milking “hay burners” into today’s expansion dairy focus on corn silage forage and oilseed proteins.     Today, whether you look at Breed Association pedigree studies or the DNA genotype patterns, a full 25% of the modern Jersey genotype comes from “Chocolate Soldier” (and note he spread the lethal recessive for early-term abortion, JH1C, to a quarter of all Jerseys) and in the world-dominating Holstein breed, 30% of the Black and White genotype comes from those two 1960s bulls “Elevation” and “Arlinda Chief”.

What made these two bulls take over the Holstein breeding world?

My personal prejudice is that each sire was bred within herds that considered the “aAa” (Weeks Analysis) Breeding Guide.    These two bulls were magnificent physical specimens expressing an exceptional degree of phenotypic “balance”  (Chief, born 1962, eventually classified “EX” at 94 points while Elevation, born 1965, eventually classified “EX” at 96 points) and this enabled them to both live functionally to 14 years of age, thus producing large volumes of semen.    Their most notable recent descendant,  Picston Shottle  (a key influence within the Holstein Genomic/ DNA “reference population”) had a similar 16 year life span at his AI stud residence in England.   The biggest “secret” in dairy cattle breeding is that “aAa” exerts more influence on breeding cows that will reach a productive maturity than any other promoted approach to matings.

As Genomic selection approaches have advanced, the frequency of “Arlinda Chief” genes also advances.     Comparing “Arlinda Chief” to “Elevation”, you have a truly linebred bull in “Chief” (eight close crosses to ABC Reflection Sovereign *RC;  over 20 crosses to the originating bull of the “Rag Apple” bloodline, Johanna Rag Apple Pabst) – while you have an example of the old practice of line crossing in “Elevation”  (his sire an inbred son of linebred Wis Burke Ideal;  his dam a linebred descendant of Johanna Rag Apple Pabst with NO ancestry from the mentioned ABC Reflection Sovereign *RC so important in “Arlinda Chief”s “Rag Apple” heritage).

Outcrossing within a breed generates similar heterosis (“hybrid vigor”) as crossbreeding.

When you cross a linebred bull with the equally linebred descendants of another linebred bull, but with those two sires appearing to be “outcross” to each other, you can generate a “hybrid vigor” response in purebred matings that is often as powerful as the first cross results from a “crossbreeding” scheme.   In fact, as far as Holstein breed progress since frozen semen came on the scene allowed better linebred bulls access to unrelated cows across the country (1955 in Ontario, 1957 at ABS, 1959 at Curtiss, 1963 at Carnation) the casual pedigree relationships in AI service produced a rising “inbreeding coefficient”.     Some University extension people became concerned, taught their captive state AI cooperatives to preach against “inbreeding”, and the result was a demand for AI mating services to consider inbreeding in mating suggestions.   So we might ask—how successful was this focus?     Dr Les Hanson of University of Minnesota is an example of a geneticist who predicted “the Holstein breed is getting so inbred that it could be obsolete in 10 years—the only solution will be to crossbreed” (which resulted in the “Pro Cross” concept promoted until recently from southern California).     He made this prediction over 30 years ago, but in spite of increasing efi% across commercial dairies, the Holstein still survives.

With Genomic mating selection, however, today’s sire offerings differ from what most AI studs offered between 1960 (when lots of bloodlines were represented) and 2000 (when sire lines were down to Ivanhoe (mostly through “Bell”), Arlinda Chief and Elevation.     The “heterosis” remaining in Holsteins came from the diversity of cow lines competing for AI attention.    It was also true that a plurality of the more successful breeders of AI stud bulls followed “aAa” matings in which the Breeding Guide avoids the mating of “likes to likes” at the level of physical genes.    Thus these donor cows who produced successful sons retained outcross vigor against the AI-generated mating sires who were increasingly sire line concentrations.

Farnear Delta Lambda  (late of ST Genetics) is a textbook example of Genomic matings
This bull recently died at the point where his oldest daughters were first calving.    He follows a pattern among the Genomic success stories—( McCutcheon, Mogul, now Lambda ) – unable to live a full productive life.    Why do these sires expire so much younger than the more famous of their progenitors?    Perhaps all this emphasis on “fast maturity” genetics is mainly giving us an “accelerated aging” of their physiques??

“Lambda” has 50 pedigree crosses to SWD Valiant, perhaps the most revered of the early sons of Pawnee Farm Arlinda Chief.     “Lambda also has 25 crosses to Walkway Chief Mark, perhaps the last of the successful sons of Pawnee Farm Arlinda Chief.     Both “Valiant” and “Chief Mark” were pedigree outcrosses to Round Oak Rag Apple Elevation.    They both had “round” (code 4 aAa)  front ends, but were otherwise “sharp” (code 2 bodies and udders, code 3 rear ends)  in physical expression, relating to qualities that can use a corn-oilseed based ration to make milk.    You will find similar concentrations of blood to various high profile bull ancestors in the noted Genomic “success stories”.         So why do these bull studs caution you to avoid “inbreeding” seeing they are so enthusiastically following the practice themselves??