A different view on veterinary medicine and global food security
In her recent letter to the editor, Dr. Reyes-Illg1 asserts that “the livestock sector is responsible for roughly 18% of greenhouse gas emissions, a higher share than that attributed to transportation,” citing a report2 from the Food and Agricultural Association of the United Nations. However, that report was released in 2006, and the calculations have since been drastically revised downward. More recent reports conclude that total emissions from global livestock production represent 14.5% of all anthropogenic greenhouse gas emissions3 and production of livestock in the United States contributes < 4% of all US greenhouse gas emissions.4 Additionally, approximately 40% of feeds for high-producing dairy cattle are byproducts of human food and fiber production, including almond hulls, beet pulp, cottonseed, distillers’ grains, canola meal, crop residues, and cull fruits and vegetables. Almond shells and rice hulls are used as bedding materials and end up in compost, which is subsequently used to improve soil quality. Manure liquids and solids are used as fertilizer, decreasing reliance on commercial chemicals. Furthermore, California dairies have managed to reduce their methane emissions by 25%5 while also providing renewable natural gas to the energy and transportation sectors.
Dr. Reyes-Illg also claims that increasing animal production efficiency has detrimental impacts on the well-being of livestock. To attain high production efficiency, however, producers must enhance animal welfare. Terms such as “cow comfort,” “cow cooling,” and “humane movement of cattle” have become routine in the modern dairy industry. Many farms participate in third-party audited programs such as the FARM animal care program delivered by the National Milk Producers Federation.6 Improving livestock treatment, nutrition, and housing leads to increased production with lower rates of disease and injury. Additionally, comprehensive mandatory nutrient management plans lead to efficient waste recycling and appropriate nutrient flows between land and livestock.
A food product's carbon footprint is directly linked to the efficiency of its production. Improving efficiency through increased yield, decreased feed conversion, and improved animal well-being all dilute the fixed carbon costs. A cow producing 10 gallons of milk/d has a much smaller carbon footprint per gallon produced than a cow producing 5 gallons of milk/d.
In closing, contemporary, efficient animal agriculture systems minimize their carbon footprint by increasing the efficiency of production and improving the stewardship of livestock and the land. Increased efficiency can be accomplished in numerous ways including humane treatment of the animals, genetic selection, better feeding strategies, use of information technology, and investing in newer, cleaner equipment. One specific and essential nutritional step is feeding agro-industrial byproducts to convert biomass of no commercial value into high-quality protein. Ultimately, diluting the carbon footprint per unit of food produced is the solution to providing global food security. That perspective is important when considering the consumption of animal food products.
Robert B. Cherenson, DVM
Lander Veterinary Clinic Turlock, Calif
1. Reyes-Illg G. Veterinary medicine and global food security (lett). J Am Vet Med Assoc 2020;256:1203.
2. Food and Agriculture Organization of the United Nations. Livestock's long shadow. Available at: www.fao.org/3/ao701e/aO701e00.htm. Accessed Jun 10, 2020.
3. Gerber PJ, Steinfeld H, Henderson B, et al. Tackling climate change through livestock—a global assessment of emissions and mitigation. Rome: Food and Agriculture Organization of the United Nations, 2013. Available at: www.fao.org/news/story/en/item/197623/icode/. Accessed Jun 10, 2020.
4. University of California, Division of Agriculture and Natural Resources. Livestock's impact on greenhouse gases and California's rangelands. Available at: ucanr.edu/News/Trending/Livestock_and_greenhouse_gas/Livestock%E2%80%99s_Impact_on_Greenhouse_Gases_and_California%E2%80%99s_Rangelands/. Accessed Jun 10, 2020.
5. California Department of Food and Agriculture. California Department of Food and Agriculture awards nearly $102 million for dairy methane reduction projects. Available at: www.cdfa.ca.gov/egov/press_releases/Press_Release.asp?PRnum=19-085. Accessed Jun 10, 2020.
6. Farmers Assuring Responsible Management. FARM and you. Available at: www.nationaldairyfarm.com. Accessed Jun 10, 2020.
Further input on veterinary medicine and global food security
In her recent letter, Dr. Reyes-Illg1 expresses concern regarding the impact of animal protein-based food production on climate change through the production of greenhouse gases (GHGs). However, the cited report2 from the Food and Agriculture Organization of the United Nations compares direct and indirect GHG emissions from the livestock sector with direct emissions from the transportation sector, as pointed out by Pitesky et al.3 In addition, GHG production attributable to livestock varies substantially by region. For instance, the US Environmental Protection Agency4 reports that the entire US agriculture sector accounted for only 10% of domestic GHG production in 2018, whereas the transportation sector accounted for 28% and the electricity sector accounted for 31%. Emissions from livestock represent 39% of total agriculture sector emissions, or approximately 4% of domestic GHG production.
Cattle produce methane as part of their normal digestion. Methane is approximately 28 times as potent as CO2 regarding effects on climate change but lasts for a far shorter period than CO2(10 years vs hundreds to thousands of years).5 However, cattle are also part of the drawdown of carbon from the atmosphere. Much of the arable land mass of the globe is not suitable to produce plants that can be eaten by humans. Such land includes the United States’ vast grasslands, which remove CO2 from the atmosphere through photosynthesis and are where beef cattle are raised. Cattle consume plants that are indigestible to humans and convert them through rumination into human-digestible protein (beef and dairy products).
Growing corn, which is a grass, is another mechanism whereby carbon is removed from the atmosphere. It is a misconception that most of the corn produced in the United States is diverted to feeding livestock. Approximately 36% of US corn production is used to feed cattle, poultry, and swine in the United States6; however, these animals also consume byproducts that would otherwise end up in landfills, producing methane as they decompose. Cattle consume grass for most of their lives and are fed grain only during the finishing period. Interestingly, animals consuming grain-based diets produce less methane emissions than do animals consuming grass-based diets. Cattle are the ultimate upcyclers in this regard, using energy from the sun and CO2 from the atmosphere to produce high-quality human-edible protein.
Notably, per capita beef consumption in the United States has decreased since the 1970s, but metabolic disease and obesity rates have increased. Replacing animal-derived food sources in the American diet with carbohydrates and sugar from plants could be associated with this human nutritional problem. When discussing climate change, focusing on livestock GHG emissions not only misses the major contributors to GHG emissions but can have the unintended consequence of creating greater food insecurity by advocating for diets that are not nutritionally sound.
K. Fred Gingrich II, DVM
Executive Director American Association of Bovine Practitioners Ashland, Ohio
1. Reyes-Illg G. Veterinary medicine and global food security (lett). J Am Vet Med Assoc 2020;256:1203.
2. Food and Agriculture Organization of the United Nations. Livestock's long shadow. Available at: www.fao.org/3/a-a0701e.pdf. Accessed Jun 8, 2020.
3. Pitesky ME, Stackhouse KR, Mitloehner FM. Clearing the air: livestock's contribution to climate change. Adv Agron 2009;103:1–40.
4. US Environmental Protection Agency. Sources of greenhouse gas emissions: agriculture sector emissions. Available at: www.epa.gov/ghgemissions/sources-greenhouse-gas-emissions#agriculture. Accessed Jun 3, 2020.
5. US Environmental Protection Agency. Overview of greenhouse gases. Available at: www.epa.gov/ghgemissions/overview-greenhouse-gases. Accessed Jun 3, 2020.
6. National Corn Growers Association. Corn usage by segment 2019. Available at: www.worldofcorn.com/#corn-usage-by-segment. Accessed Jun 3, 2020.
