USDA performed extensive crossbreeding trials among Holstein, Guernsey, Jersey, and Red Danes at the Beltsville Experimental Farms in the 1940s and 1950s, concurrent with the beginning of AI. After all crossbreds were compared to contemporary purebreds (which also included some inbreeding trials), the experiment was concluded with two conclusions “Nothing crossbred or purebred will milk more than a straight bred Holstein” and “Avoid inbreeding”.
Thus while ABS in its early days had advocated crossbreeding, all other studs jumped on the “purebred” bandwagon and dairy crossbreeding died out. If anything, “crossbreed upgrading” became the norm for those who bred colored cows to Holstein sires once the 1960s ushered in the “Class” based Federal Milk Orders, and added bottling premiums to what had been a butterfat based milk pricing system.
Holsteins peaked at 96% of the USA and Canadian cow populations, and many “experts” predicted the demise of all other dairy breeds. At the same time, in the 1970s, the concept of “index ranking” took charge of the genetic evaluation systems, and each breed association eventually fell in line, accepting a “sire stack” contemporary comparison genetic theory, over purebred concepts of “maternal cow lines” and intergenerational phenotypic comparisons. The culmination of these changes was “linear trait” type appraisal replacing traditional breeder-designed type grading standards.
Indexing accelerated milk production at younger ages. Linear selection made dairy cows highly angular (which is genetically linked to early production maturity) -- the milk check was the only selection value.
Multiple Component Pricing arrived in the north half of the USA in the 1980s, with protein taking its place alongside butterfat as the driving forces behind changing consumer demands, and colored cows started a comeback that continues today (rebuilding gene pools later tapped for crossbreeding).
By the 1990s, it was clear that many dairy farms were in trouble both operationally and financially, and those who study economic trends eventually looked at the dairy cows themselves. The higher yield AI cows had become “high maintenance” cows as well, and the capital costs of remodeling dairy facilities to provide the “model” environment dictated by “ideal” genetics became too high to generate a positive rate of return on investment (even as the milk check cashflows continued to grow).
Enter crossbreeding. Alternative farm designs, such as intensive grazing, higher forage rations, less external inputs, less elaborate barn designs, group handling, all brought the highly specialized Holstein cow into question. Industry logic was “we have been using the best bulls” [note: “best” as defined by prior assumptions] thus “the fault must be in pure breeding—we now must crossbreed to regain vigor, health and fertility”. Overlooked was the continued success of “aAa” herds using the same sire pool.
What has been consistent in selection of “cross” breeds? Every breed (starting with Jerseys, then Brown Swiss, then Swedish Red, then NZ Friesian, then Montbeliarde, then Norwegian Red, and now Fleckveih) that has had a major part in crossbreeding added “round” qualities on some physical level to the razor-back “sharp” Holsteins. On a summary level, it was that simple. The experts advocating crossbreeding spoke lots of pseudo-science to justify it (“heterosis response”) (“too much inbreeding”) (“higher health trait gene base breeds”) – but it turns out, the old concept of the “dual purpose” breed cow’s physique was just healthier and more reproductive than the “modern” cow.
“Round” and “Sharp” are the most basic of “aAa” mating concepts. Could it all be that simple??
All I know is, both purebred and crossbred herds using “aAa” are happier about their cows.