By Greg Palen
The numbers game in dairy genetic selection began when the AI industry switched to frozen, storable semen in the 1960s, thus providing a true choice of sires. This was the beginning of the genetic horse race for the best sires, and the long battle to define the word “best.”
Fads came and went. Genetic ranking shifted from pounds of butterfat to pounds of milk (and later protein). Universities partnered with feed companies to figure out how much grain a dairy cow would eat without getting sick, then studied “type” to determine traits most responsive to making milk in volume at younger ages. Breed type classification became a tool for bull evaluation. Ultimately, we accepted the idea of ranking bulls on a composite of milk yield and type traits. PD for each trait gave way to Net Merit, TPI and other data formulas that we could treat as a “single trait selection” process.
With each of these, the competition for genetic ranking pushed from consideration the preservation of genetic variation. Entire bloodlines disappeared from AI due to being obsolete according to the index that happened to be in vogue. This almost led to a wholesale elimination of breeds other than Holstein whose physical trait selection histories made them less fit as “grain burners.”
The population geneticists and AI systems saw rising herd averages and bigger bull numbers. Genetics took all the credit it could, even though it became clear that if you build a new freestall barn and parlor and convert to TMR feeding, the cows will give more milk. Dairy technology adopters were psyched up to invest in the latest sire ranking indexes and linear breeding concepts.
This mindless pursuit of the numbers started producing frailer physiques and slower fertility, more metabolic and respiratory disease, more hoof trimming, more stillborn calves and shorter herd life. So geneticists invented health traits, rediscovered “inbreeding” in the similar sire stacks, and created “Genomics.”
Graziers join the party
Meanwhile, a few dairymen rediscovered pasturing on the New Zealand model, named their epiphany “grazing,” and proceeded to increase their profitability by producing a bit less milk at a much lower cost. Some lucky cows were turned outside and told to use their instinctual DNA to find their own lunch. Some did better than others; we saw that some cows failed to “adapt” to grazing. Graziers sought expert opinion, and all the simplistic answers started coming:
• Holsteins are just too big. You need to switch breeds, milk smaller cows.
• Purebreds struggle with inbreeding. You need the hybrid vigor of crossbred cows.
• You’re selecting the wrong index. You need the grass-based Kiwi BW index.
• Small cows don’t milk enough. You need bigger, dual-purpose European Reds.
It is easy to understand why we fall into shortcut traps. When we buy seed, we buy a single variety for the entire field based on its “composite index” of desired traits such as emergence, digestibility, grain energy and yield. So we keep listening to experts who think cow genetics should work the same way: just select the highest ranked sire on this index and breed the entire herd to him, just switch breeds and all your troubles will go away, just crossbreed for hybrid vigor.
But it is a proven fact that cow lifetimes are more complex than annual crops. It is proven that in cattle, single trait selection generally fails after three generations. Research shows it leads to “selection depression,” which is the real inbreeding effect. Population genetics has not perceived the single-trait nature of rankings.
Hybrid vigor limited
Meanwhile, whether outcrossing or crossbreeding, the data show that hybrid vigor dwindles after three generations. If pedigree and index rank are your only selection criteria, your herd will start going downhill at some point.
Thus, 15 years into a farm’s transition to grazing, too many dairy people are wondering why they feel as if they’ve hit the wall. Because all the emphasis has been placed on seeds planted, rotations followed, seasonal breeding and all the other mechanical aspects we love to debate, the possibility that simplified genetic approaches are failing us never occurs to enough people.
The really big thing here is that how you pick the sires is probably more important than how you pick breeds. In time, the linear approach based on breeding likes to likes — in both traits emphasized and physiques selected — will fail a grazier just as often as it fails a confinement dairyman.
The single most important genetic concept to follow is that “the genes you select must adapt to the environment you made.” Following that must come “the cow has equal input to the bull in the calf that results from your selection system.”
Theoretical genetics’ two major assumptions — establish genetic value separated from any environmental influence, and all gains from genetic selection come from the sire side — can be shown to be flawed due to the percentage of culls it produces.
The experts who say “select on this index” or “cross with this breed” or “linebreed with this bull” live under the illusion that a formula produces the same result every time, even though any high school biology student will tell you that combining genotypes to produce new life is a process designed to maintain gene variety — unless you allow only certain genes into each generation (producing extremely tall Holsteins and other freakish extremes).
Genes behave in one of three major ways: quantitative (directional), qualitative (biophysical) and interactive (environmentally triggered). The genetic rankings stick to the quantitative (linearly measurable) traits, where we have learned that if we always select for stature, cattle keep getting taller. And it’s also true that if we select away from size, cattle keep getting smaller. No formula seems to average out between all the linear extremes to allow us to optimize at a desired size.
The qualitative characteristics are the focus of aAa Breeding Guide (Weeks’ Analysis) and its imitators. They recognize that a cow’s physique can be either “balanced” and thus “low maintenance” —meaning they are adaptable to any environment — or “specialized” and thus “high maintenance” — only adaptable to some specific, idealized environment. They look at the interrelationships between form, function and the physique as a whole, rather than the sum of linear parts.
Let’s get back to our seed analogy. While the mating has already been done in the seeds you plant, you have to choose a mating for each cow. To get what you want, you may have to violate the recommended index by selecting bulls on a matrix of traits you desire in this generation, updating each generation based on the results.
Move beyond slogans
The point is that we need to get beyond these simplistic “you need a small cow to succeed in grazing” concepts that offer no genetic blueprint for future cows that can optimize between production, reproduction and maintaining a healthy life. We need practical breeding programs in which both the qualitative and the quantitative are managed in favor of all the traits and qualities we wish our cattle to possess.
We need to translate gene inputs into the kinds of cows that produce a competitive volume of high-value milk at production costs below market prices. We need to grasp genetic selection as biology, not just numbers. There are no shortcuts. There is only selection priority dictated by the limitations and opportunities of your farm and your management.
Greg Palen grazes polled Jerseys near Ovid, Michigan, and is an analyzer with aAa Dairy Cattle Breeding Guide.