How do farmers decide which cows to breed and which to put out to pasture?<\/p>\n
Historically, farmers have selected cows with genetics for better milk production and quality. More milk means more supply and more money in the farmer\u2019s pocket.<\/p>\n
But due to rising temperatures around the globe, cows that can handle the heat are becoming more desirable.<\/p>\n
\u201cAnimals with high milk production tend to be worse at dealing with heat stress,\u201d says Breno Fragomeni, assistant professor of animal science<\/a> in the College of Agriculture, Health and Natural Resources<\/a>. \u201cWe need to start selecting animals also for heat tolerance or else that selection for high production is not going to work,\u201d Fragomeni says.<\/p>\n Fragomeni is using cutting edge genomic research to determine how to make dairy cattle better adapted to heat stress.<\/p>\n Failing to select for heat tolerance could result in lower food production which will increase food prices and food insecurity. Additionally, cows that are naturally better able to bear the heat will be more comfortable, ensuring increased animal welfare.<\/p>\n To conduct his research, Fragomeni and his team collect more than 20 kinds of data including how much milk the cows produce, protein and fat yields, cell count, and when and how often cows reproduce. They compare these data with temperature and humidity data.<\/p>\n When cattle are stressed, one of the first observable impacts is a decrease in milk production. This is likely because eating and digesting generates a lot of heat in cows\u2019 bodies. So, when cows get heat stressed, they eat less and hence produce less milk.<\/p>\n Fragomeni has found that for every degree above 65 on the temperature humidity index (THI), milk production at the Kellogg Dairy Center decreases by 0.2 pounds of milk per cow. On an extremely hot day, this could cause a total loss of 500 pounds of milk in the facility.<\/p>\n \u201cWhen you talk about heat stress, people usually imagine animals dying from the heat,\u201d Fragomeni says. \u201cBut in dairy farms, the animals are slightly stressed. It\u2019s not that they\u2019re suffering in such a way that they can\u2019t cope anymore. They\u2019re still producing milk, it\u2019s just a little bit less.\u201d<\/p>\n This estimated 5% drop in production during the summer could mean ending the year at a loss rather than a profit for dairy farmers, who operate with very narrow profit margins. The dairy industry loses an estimated $1.2 billion from heat stress annually.<\/p>\n Additionally, when the cows are heat stressed in the summer months, they don\u2019t want to conceive. They wait until temperatures drop in fall to get pregnant. This means calves are born in the heat of summer. On top of the stress of giving birth and producing milk at their maximum for their calves, the cows experience more and more heat stress.<\/p>\n \u201cThat\u2019s when the cow needs more comfort, but it\u2019s also when the cow is being most stressed by the high milk production and recovering from the delivery,\u201d Fragomeni. \u201cIt becomes a cycle.\u201d<\/p>\n There is no single gene that alone solves the heat stress problem. Fragomeni looks at the complete genomes of bulls that have hundreds of daughters and sees whose daughters are better suited to handle the heat.<\/p>\n \u201cHeat stress tolerance is a very complex trait. We have hundreds if not thousands of genes involved,\u201d Fragomeni says. \u201cAt the end of the day, selecting for a single or a few markers is not going to make a lot of difference.\u201d<\/p>\n Using a sophisticated statistical model, Fragomeni and his team associate milk production with temperature using a national database of bull genetics. The model creates an estimate of how much milk a cow is expected to lose relative to the national average based on their sire.<\/p>\n Without using genomics, it would take approximately five years for scientists to be able to determine if a bull is genetically well-suited for heat.<\/p>\n \u201cIf you\u2019re not using genomics, we can only tell if the bull is good or not after we have so many daughters with complete lactation records and that takes a while,\u201d Fragomeni says.<\/p>\n Passing this information along to farmers helps them decide which bulls to seek as sires so their offspring are better suited for heat while still being high milk producers.<\/p>\n While some farms do have cooling systems in their barns, for many, installing expensive air conditioning systems is not feasible, making genetic solutions much more sustainable.<\/p>\n \u201cSome of these environmental interventions may be a challenge or cost prohibitive for some farms,\u201d Fragomeni says. \u201cHowever, we\u2019re going to spread heat tolerant genetics across the whole population and hopefully on the long-term we\u2019re going to have better animals for that.\u201d<\/p>\n Fragomeni is currently working on a study using milk and fecal samples from cattle at the Kellogg Dairy Center to determine if heat stress changes the animals\u2019 microbiomes.<\/p>\n This study is part of an effort to develop better non-invasive measurements for heat stress. Currently, the most accurate measures require scientists to take blood samples, respiration rate, or vaginal temperature. These methods are hard to scale up for large farms and can further stress animals.<\/p>\n \u201cWhen you\u2019re talking about specific farms, we can only tell the animals are heat-stressed after they show symptoms and it\u2019s too late for an intervention,\u201d Fragomeni says. \u201cSo, we\u2019re trying to come up with some better methods that are non-invasive.\u201d<\/p>\n Fragomeni is also working on a study comparing cattle in Wisconsin and Texas, two of the largest dairy producers in the U.S. These two states have radically different management systems and climates which could correspond to differences in the animals\u2019 genetics.<\/p>\n In Connecticut, animals experience an average of 100 days of heat stress per year. Down south, this number can be as high as 250 days a year.<\/p>\n \u201cSometimes you can cope with a cow being heat stressed less than a third of the year,\u201d Fragomeni says. \u201cSo we can keep animals that are sensitive to heat stress. While in the South, if the animal is sensitive, they just have to get rid of it. So maybe animals in the cooler regions are actually more sensitive than animals in the hotter regions. That is our hypothesis.\u201d<\/p>\n The long-term goal of this work is to identify the best genetics for cows in each climatic region of the U.S.<\/p>\n A core part of Fragomeni\u2019s research is ensuring his solutions are sustainable for farmers, consumers, and the environment.<\/p>\n \u201cThe sustainability must be economical, environmental, and social \u2013 people must be able to afford food,\u201d Fragomeni says. \u201cWe\u2019re not trying to come up with things that are unrealistic for the farmers.\u201d<\/p>\n <\/p>\n This work relates to CAHNR\u2019s Strategic Vision area focused on\u00a0<\/em>Ensuring a Vibrant and Sustainable Agricultural Industry and Food Supply.<\/em><\/a><\/p>\n