Selective breeding and carbon footprints
The carbon footprint of dairy production
Artificial insemination allows bulls with superior genetics to have far more offspring than would be possible using natural breeding. These superior genetics have led to an astonishing rise in cow productivity in the last century. While the number of dairy cows in the U.S. has fallen from around 17 million to 9 million since 1960, total milk production has rise 40%. How? Because each cow is producing more milk. A lot more! 1960 the average cow produced about 755 gallons (or 6,493 lbs) of milk per year, while today she will produce over 2,326 gallons (or 20,000 lbs). Each dairy cow today produces about 200% more milk compared to one in 1960!(G1,N1)
Figure 1—U.S. dairy production over time (all units on a per annual basis)
This is a picture of what it takes to produce one gallon of milk today: 2 gallons of water and roughly 10 lbs of feed (that feed consists of Alfalfa hay, bermudagrass hay, cotton seeds, corn, soybean meal, and various vitamins and minerals).(C1,D2)
Figure 2—What the cow needs to make one gallong of milk today
In 1945 it would have taken five times the amount of feed and water to produce that same gallon of milk—a remarkable improvement in productivity, which both reduces the price of milk and lowers the carbon footprint associated with one gallon of milk (if fewer inputs are needed to produce one gallon of milk, that corresponds to fewer carbon emissions). In fact, the carbon footprint of a gallon of milk in 1945 was almost three times greater than the footprint today!(C1) (Note that “carbon” refers to carbon-equivalent emissions. For instance, methane is a greenhouse gas that creates 21 times the warming of the same amount of carbon, but instead of saying “one ton of methane” I say “21 tons of carbon”.)
That does not mean that the total carbon emissions from dairy production has fallen, as more milk is produced in the U.S.. than in 1945. Let X be the total carbon emissions from dairy production in 1945. If the same amount of milk were produced today the new level of emissions would be (1/3)X. However, milk production has risen 68% since 1945, and so the new level of carbon emissions from all the milk produced in the U.S. is (1.68)(1/3)X = 0.56X. Consequently, a rough calculation suggests dairy production today leads to about half the total carbon emissions compared to dairy production in 1945, despite producing much more milk.
Cows are producers of methane, a greenhouse gas, and they expel methane as they burp, which can be as often as once a minute. So being able to get more milk out of a single cow is like getting more milk for each lb of methane emitted, allowing us to consume foods we enjoy while benefiting the environment at the same time.
Of that surge in productivity in the last fifty years, 2/3 is due to better genetics, and 1/3 is due to better management and feed.(D1)
Figure 3—What the cow needs to make one gallon of milk in 1945
This attention paid to genetics is a rather recent part of running a dairy farm, when viewed from the long timeline of agriculture.
Selective breeding in dairy cattle
Up until around the time of Henry VIII in England, little care was given to what cows would be bred with another. In another lecture I talked about how King Henry enclosed the commons and converted it to private property, giving big landowners the monetary incentive to increase productivity. At the time, cattle were better described as different races in each region as opposed to different breeds. Each region had its own particular genetics, and people were not eager to import the genetics of other regions.(F1)
The black and white cows you see here—and in every Chick-fil-A commercial—are referred to as Holsteins in the U.S. and Friesians elsewhere. Every now and then a recessive gene will cause them to be red and white. They are called Holsteins or Friesians because this line of cattle was developed in both the Friesland of the Netherlands and the Holstein region of Germany. These cattle were imported to the U.S. at different periods, but most of today’s U.S. Holstein cattle can trace their ancestors back to the imports arriving between 1877 and 1905,(D1) and are the most popular dairy breed because of their superior milk production.
Figure 4—Origin of the Holstein breed
Figure 5—Holstein breed
The smaller brown cows are Jersey cattle, which originated from the Isle of Jersey in the English Channel. Although a single Jersey produces less milk than a Holstein, Jerseys convert feed to milk more efficiently (Holsteins therefore produce more because they eat more). This farm had only a few Jerseys until the price of corn rose to historical levels, at which point they integrated more Jerseys for their more efficient conversion of feed to corn. Milk from Jersey cows are also higher in butterfat, and if butterfat is scarce relative to fluid milk, the output of Jersey cows can elicit a higher price than their Holstein counterparts. For these reasons Jerseys can be more or less profitable than Holsteins, based on the price of feed and consumer demand for milk, cheese, and butter. (G1)
Figure 6—Origin of Jersey breed
Figure 7—Jersey breed
Interestingly, while the Jersey cows are gentle and have an gregarious personality, the meanest animal I have ever seen in my life was a Jersey bull. I hear Holstein bulls are no better.
Until 1750 very little attention was given to the bull that would be used, when today that is the most important choice a farmer can make. This might be because they had no system for collecting data and so no good system for designating which bulls were superior. The quality signals they relied on were flawed. When a farmer in the Elizabethan Age set about trying to determine whether a cow would produce a lot of milk they might look at the direction of its hairs on the rear part of an udder, a custom which had about as much validity as the many superstitions that existed at the time.(F1)
Today, milk production is a highly advanced science, and an enormous data collection program has been established, allowing dairy producers to use statistics—not myths or tradition—to identify the best genetics.
So if the carbon footprint of your milk is a major concern for you, then nothing is more important that the semen the farmer buys to impregnate the heifer. The good news is you don’t need to worry about whether the farmer is reducing the carbon footprint of milk. The farmer has even more incentive than you to get more milk with fewer inputs, and so this increase in productivity and reduction in carbon footprint over the last century came about by farmers doing what they do best: increasing the productivity of their animals. It came about out of the farmers’ self-interested pursuit of profits, not concern for the environment, as global warming did not exist as an issue in 1945.
The same thing goes for better nutrition, the second most important reason for higher dairy productivity. Before the 16th century a lot of farmers would slaughter much of their livestock in the fall because they couldn’t produce enough feed to carry them through the winter. This first changed once they learned to grow turnips for a winter feed. Over the next few centuries small advancements in nutrition were made, but still, even in 1900, the science of nutrition was hardly a science at all.(A1,M1)
Now, more thought is given into what these cows eat than what we feed our pets—or even ourselves. Today, computer programs are used to determine exactly what cows will be fed, and this program is used to deliver exactly what the cow needs at each stage in its life at the least cost. Farmers can purchase some of these programs themselves to determine their feed formulations, use free programs provided by university scientists (like the Spartan 3 program by Dr. Hutjens at the University of Illinois), or hire consultants to design feed formulations for them. Whatever strategy is taken, the feed will be determined based on the the size of the cow, whether the cow is lactating, an enormous amount of data on nutrition requirements and milk prices, and a computer optimization routine to make sense of it all. This is one reason why students in agricultural economics and animal science learn mathematical optimization algorithms in college. Since roughly half of the dairy farm’s cost is feed,(D1) and since small deficiencies in nutrition can cause considerable shortfalls in milk production, a farmer can thrive or go bankrupt based on her feeding strategy.
Figure 8—Computer program to formulate dairy cattle feed
(Accessed January 6, 2013 at http://www.youtube.com/watch?v=37bHvCG92zc)
Figures
(1) Original figure. Sources: G1 and N1.
(2-3) Original figure. Sources: D2, and G2
(4) Maps taken from Wikimedia Commons (source is in the picture)
(5) Photo from DASNR Kitchen Sink
(6) Maps taken from Wikimedia Commons (source is in the picture)
(7) Photo from DASNR Kitchen Sink
(8) Screenshot from YouTube.com