Overview
- The Cornell analysis, published Friday, compared 2007–2016 records for about 6.5 million cows with 2.5-mile grid weather data across 43 states to link heat stress to falls in both milk yield and milk fat and protein.
- Researchers calculated that a 10-point rise in the temperature-humidity index corresponds to a 1.2% drop in milk volume and a 2.8% fall in annual revenue, which the team estimates equals about a $1.65 billion loss for the U.S. dairy sector.
- The study found milk fat and protein begin to dilute at much lower heat levels than yield loss, with composition effects appearing on days in the 60s and 70s Fahrenheit and occurring year-round.
- The team saw almost no variation in heat response by cow age, farm size, or region, suggesting limited biological adaptation so far and that the main adjustment has been where producers locate or invest in infrastructure.
- Authors and reporting outlets say the results raise risks of continued farm revenue pressure and consolidation and call for daily, cow-level data to identify heat-resilient animals and better target management responses; NASA data cited in coverage also documents large livestock losses from extreme heat and cold.