Contemporary Selective Breeding. Cow Edition.
Ed Yong has a fascinating post about a new evolutionary biology study on cow milk and the differences for male and female offspring. If you are interested in animal husbandry and/or evolutionary biology it’s an interesting read especially if you follow through with the links, especially this one.
For the purposes of this blog, I’d like to underline something that Ed’s post alludes to but doesn’t call out specifically.
For decades, the dairy industry has used data to supercharge the humble black-and-white Holstein cow into a milk-producing machine. Across the US, thousands of dairy farmers keep assiduous records about how much milk their cows produce, and the volume and composition of that milk. All of this information feeds into mathematical models that predict the total amount of milk a cow makes over its lifetime. Farmers use this information every day to decide how to care for and breed their animals. As a result, cows today make four times more milk than they did in the 1940s.
. . . Either way, Hinde’s results have implications for the dairy industry. If they wanted to, dairy managers could ensure that most of the calves they breed are females, but they’d need to separate semen by sex to do so. In the past, some people have argued that this isn’t cost-effective, but it might be worth it if it leads to a 2.7 percent bump in milk production.
I think a lot of the conversation around food in this country (and around the world) is hamstrung by the naive, sentimental and sometimes schizophrenic vision many people have of agriculture.
Ed Yong’s post alludes to two things.
First. Modern selective breeding is much more specific and sophisticated than most people realize. In the last hundred plus years, selective breeding has produced much more substantial changes in domesticated animals and crops than people realize. Many amateur ‘critics’ of contemporary agriculture believe that selective breeding means farmers are just mating their healthiest males with their healthiest females in a parallel to survival of the fittest in nature. In their objection to genetic engineering they say that we should stick with our food the way it is, as nature intended. They seem to be completely unaware of how drastically we have engineered the genetics of domesticated plants and animals without recombinant DNA technology. They seem to be unaware that the market for bull semen goes back decades. They seem to be unaware that contemporary plant breeders use tissue cultures and genetic marker assisted breeding in their work. Selective breeding hasn’t been about capitalizing on serendipity for a long time. It works toward very clear, pre-defined goals.
Allow me to risk setting up a strawman argument. You can sometimes hear from the same quarters a pair of schizophrenic claims. In one context, people might say our health problems began 10,000 years ago with the introduction of agriculture and selective breeding. The claim is that humans haven’t been able to co-evolve to thrive on domesticated grains/wheat, as fast as we’ve been able to breed the grains for yield. The same has been said about cow’s milk. (The evidence though seems to go the other way on that count. Europeans actually evolved lactose tolerance very quickly.) In another context, the issue becomes that the (supposed) increase in chronic disease (allergies, autism, insert health problem du jour) in the last three decades must be caused by the rapid changes to agriculture in the last three decades. Our problems are either being caused by the Sumerians or Monsanto.
Where things can get really schizophrenic is when goalposts start getting moved as misinformation and misunderstanding is addressed. It’s about nutrition. No it’s about animal welfare. No it’s about food access and affordability. No, it’s about family farms. No it’s about the environment. I would argue that this stems from the fact that the pastoral sentimentality that drives so much of the current food conversation is really an aesthetic proposition. The arguments to defend that proposition shift as each is found wanting.
The second thing that Yong’s piece touches on is the positive environmental impact of contemporary breeding. I’ll let the Alexis Madrigal piece that he links to in his introduction make the case.
Dairy breeding is perfect for quantitative analysis. Pedigree records have been assiduously kept; relatively easy artificial insemination has helped centralized genetic information in a small number of key bulls since the 1960s; there are a relatively small and easily measurable number of traits — milk production, fat in the milk, protein in the milk, longevity, udder quality — that breeders want to optimize; each cow works for three or four years, which means that farmers invest thousands of dollars into each animal, so it’s worth it to get the best semen money can buy. The economics push breeders to use the genetics.
The bull market (heh) can be reduced to one key statistic, lifetime net merit, though there are many nuances that the single number cannot capture. Net merit denotes the likely additive value of a bull’s genetics. The number is actually denominated in dollars because it is an estimate of how much a bull’s genetic material will likely improve the revenue from a given cow. A very complicated equation weights all of the factors that go into dairy breeding and — voila — you come out with this single number. For example, a bull that could help a cow make an extra 1000 pounds of milk over her lifetime only gets an increase of $1 in net merit while a bull who will help that same cow produce a pound more protein will get $3.41 more in net merit. An increase of a single month of predicted productive life yields $35 more.
. . . One reason for the change in breeding emphasis is that our cows already produce tremendous amounts of milk relative to their forbears. In 1942, when my father was born, the average dairy cow produced less than 5,000 pounds of milk in its lifetime. Now, the average cow produces over 21,000 pounds of milk. At the same time, the number of dairy cows has decreased from a high of 25 million around the end of World War II to fewer than nine million today. This is an indisputable environmental win as fewer cows create less methane, a potent greenhouse gas, and require less land. . .
. . . While we may worry about the use of antibiotics to stimulate animal growth or the use of hormones to increase milk production by up to 25 percent, most of the increase in the pounds of milk an animal puts out over the pastoral days of yore come from the genetic changes that we’ve wrought within these animals. It doesn’t matter how the cow is raised — in an idyllic pasture or a feedlot — either way, the animal of 2012 is not the animal of 1940 or 1980 or even 2000. A group of USDA and University of Minnesota scientists calculated that 22 percent of the genome of Holstein cattle has been altered by human selection over the last 40 years.
In a sense that’s very real, information itself has transformed these animals. The information did not accomplish this feat on its own, of course. All of this technological and scientific change is occurring within the social context of American capitalism. Over the last few decades, the number of dairies has collapsed and the size of herds has increased. These larger operations are factory farms that are built to squeeze inefficiencies out of the system to generate profits. They benefit from economies of scale that allow them to bring in genomic specialists and use more expensive bull semen.
No matter how you apportion the praise or blame, the net effect is the same. Thousands of years of qualitative breeding on family-run farms begat cows producing a few thousand pounds of milk in their lifetimes; a mere 70 years of quantitative breeding optimized to suit corporate imperatives quadrupled what all previous civilization had accomplished. And the crazy thing is, we’re at the cusp of a new era in which genomic data starts to compress the cycle of trait improvement, accelerating our path towards the perfect milk-production machine, also known as the Holstein dairy cow.
Lastly, I think one of the things that becomes blindingly obvious from both pieces is how carefully all the input and health markers for these animals are recorded and monitored. The idea that the addition of biotech crops into their feed could be producing adverse health outcomes that have somehow evaded notice is preposterous. Unsurprisingly, when three decades of this data was reviewed, a complete absence of any problems was exactly what they found.
A new scientific review from the University of California, Davis, reports that the performance and health of food-producing animals consuming genetically engineered feed, first introduced 18 years ago, has been comparable to that of animals consuming non-GE feed.
The review study also found that scientific studies have detected no differences in the nutritional makeup of the meat, milk or other food products derived from animals that ate genetically engineered feed.
The review, led by UC Davis animal scientist Alison Van Eenennaam, examined nearly 30 years of livestock-feeding studies that represent more than 100 billion animals.
When it comes to the potential adverse effects that current biotech crops could have on birds or mammals, the argument that “We just don’t know” just doesn’t hold any water.
Study Of 1.5 Million Cows Shows Daughters Get More Milk Than Sons
Ed Yong | Phenomena | National Geographic | 23 January 2014
The Perfect Milk Machine: How Big Data Transformed the Dairy Industry
Alexis C. Madrigal | The Atlantic | 1 May 2012
An Evolutionary Whodunit: How Did Humans Develop Lactose Tolerance?
Helen Thompson | The Salt | NPR | 28 December 2012
10 Things You Didn’t Know About Bull Semen
Brian Cathcart | The Independent | 9 June 1996
Creating Tastier and Healthier Fruits and Veggies with a Modern Alternative to GMOs
Ferris Jabr | Scientific American | 23 January 2014
No sign of health or nutrition problems from GMO livestock feed, study finds
UC Davis | 25 September 2014
Prevalence and impacts of genetically engineered feedstuffs on livestock populations
Van Eenennaam and Young | Journal of Animal Science | 20 November 2014
Ferris Jabr | Scientific American | 23 January 2014