On Celsias, I recently reported on the drastic effects climate change is projected to have on key crops such as soybeans, maize, and corn. Unfortunately, rising temperatures are excepted to take a similar toll on livestock, especially dairy cows.
Scientist Terry Mader, of the University of Nebraska-Lincoln, explains that dairy production is optimal at temperatures ranging from 20-to 22°-C. “For every degree above that,” he was quoted as saying in a recent article in Scientific American, “we'll have a decline of approximately two percent productivity.” In 2006, a killer heat wave struck California, killing more than 25,000 cattle and dramatically reducing dairy production in the region. Experts estimate that the triple-digit temperatures cause a $1 billion dairy shortfall.
If existing climate models are right, temperatures in the U.S. Midwest are expected to rise at least 2° degrees if not 5° over the next century. For dairy cows, that translates into additional heat generated by metabolism and digestion along with warmer temperatures, which means the cows eat less, and they produce less milk. Mader's researchers concluded that summer milk production in the U.S. could decrease by 16-30 percent, leading of course to an increase in the price of milk.
Mader is just one of many scientist studying the potential impact of climate change on livestock. The United States National Oceanographic & Atmospheric Administration (NOAA) released its own assessment of climate change and its key effects for American agriculture last June, and the report confirmed, “Climate change clearly affects agriculture and is also affected by agriculture.”
Bill Hohenstein, director of the U.S. Department of Agriculture's Global Change Research Program Office, said the report offers a clear look at animal agriculture, showing that animals are particularly affected by extreme heat that lowers their productivity.
The report showed that due to heat, milk production in dairy operations declines, and the number of days it takes for animals to reach their target weight for meat operations increases, while the conception rate in cattle falls, and swine growth rates decline. “Swine, beef, and milk production are all projected to decline in a warmer world,” according to the report.
Some scientists, such as animal geneticist Curtis Van Tassell at the U.S. Department of Agriculture's Bovine Functional Genomics Laboratory, are aiming to produce healthier cows, thus generating greater profits for farmers and better-quality milk for consumers. Van Tassell is working with the Agricultural Research Service in conjunction with two labs, the Animal Improvement Programs Laboratory (AIPL), and the Gene Evaluation and Mapping Laboratory.
AIPL researchers are keeping track of bovine traits including milk, fat, and protein that affect cows' health, while scientists at the GEML are studying genes related to disease resistance, growth, and productivity of cows' mammary glands. The researchers are also looking at genetic markers and gene-mapping techniques to better understand the structure of dairy cows' genome. Results of research from both labs will help indentify individual genes that influence specific traits for use in breeding decisions.
Van Tassell also collaborated with scientists in Australia who are also predicting that dairy farming regions there will be affected by climate change, with rising temperatures and water shortages having a serious impact on dairy production. Researchers are combining historical milk production and weather records with genetic markers of dairy cows to determine the sensitivity of milk production to feeding levels and to temperature-humidity index on specific chromosomes.
Van Tassell and his colleagues estimate a selecting a breeding bull with genes that exhibit low temperature sensitivity could keep milk production nearly constant. Still, the question remains: which comes first, the projected 25 percent reduction in its carbon footprint promised by the National Milk Producers Federation by 2020, or genetically altered cattle better equipped to withstand climate change?
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