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The impact of extreme weather on livestock agriculture is becoming increasingly critical. A recent investigation by the University of Illinois Urbana-Champaign provides insight into the effects of heat stress on dairy production in the United States, revealing a 1% reduction in annual milk yield due to high heat and humidity. Smaller farms are particularly vulnerable compared to larger operations, which often have more resources for managing these stresses.
“Cows, like humans, suffer from heat stress, which can cause various health issues. This impacts their appetite and overall well-being, leading to decreased milk production,” said Marin Skidmore, co-author of the study and an assistant professor in the Department of Agricultural and Consumer Economics (ACE) at the university. She collaborated with fellow researchers Jared Hutchins and Derek Nolan, who contributed their expertise in animal sciences and extension education.
The research team analyzed extensive milk production data from nine states in the Midwest, examining over 56 million records from 18,000 dairy farms spanning from 2012 to 2016. They refined this data by accounting for protein and fat content, essential factors that influence milk pricing.
“While previous research has primarily concentrated on volume, in our dairy market, revenue is driven by the quality of milk produced. It’s not solely about how many gallons are produced; quality matters significantly,” Skidmore noted.
To assess heat stress accurately, the researchers matched quality-adjusted production data with detailed weather information related to temperature and humidity. They utilized the temperature-humidity index (THI), a key measure indicating how heat and humidity combined can hinder cows’ natural cooling processes.
The findings revealed a significant annual loss of milk yield from heat stress, translating into approximately 1.4 billion pounds of milk over a five-year period for the farms studied, equating to an estimated $245 million in potential revenue lost. While daily variations in stress levels impact yield, the analysis indicated that extreme stress days cause more than twice the yield loss compared to days of moderate stress.
Notably, the study highlighted that smaller farms with herds of fewer than 100 cows experienced an average annual yield loss of 1.6%. These farms, although contributing to less than 20% of total milk output in the dataset, accounted for 27% of the total financial impacts due to heat stress.
Farmers can employ a range of strategies to mitigate heat stress, including ventilation systems, open barn designs, and cooling sprays. However, these measures are typically more sustainable for larger farms, which can invest more heavily in such resources. Nevertheless, total elimination of heat stress remains unattainable.
“While several adaptive techniques exist, no single solution can completely address the situation,” Skidmore elaborated. “Upgraded cooling systems and adjusting calving schedules offer some potential relief, but each approach presents its own challenges and risks.” She further explained that smaller farms often bear the brunt of manageable stress levels, whereas larger farms feel the effects less severely until temperatures rise to a critical level.
Looking to the future, the researchers estimated that milk yield losses could escalate by around 30% by 2050 due to projected increases in extreme heat days based on 22 different climate models.
Skidmore emphasized the need for policy makers to prioritize dairy production to sustain small farms in an increasingly challenging climate. “For a continued thriving presence of small dairy operations in the U.S., targeted financial support and research investments will be necessary to empower farmers to adopt effective heat stress mitigation strategies,” she concluded.
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