Estimation of the economic impact of heat stress on dairy production systems in Chile

Abstract

Abstract The estimation of the economic impact of heat stress on the dairy sector is relevant to the implementation of policies to cope with it. We collected hourly records (November-March 2017–2022) from 19 weather stations representing the eight Chilean dairy macrozones to estimate two comfort thermal indices: the temperature-humidity index (THI) and the THI adjusted for solar radiation and wind speed (THIa). The economic impact was estimated considering the losses on milk yield, days open, culling rate, and deaths based on international previous work using a critical threshold of 65. There were important differences in the number of hours above the threshold among dairy production macrozones, independent of the thermal index used. The greatest values were observed in macrozones I, II, and VIII, where most of the dairy cows are located. Average losses in milk yield were between 1.75 to 6.09 times higher when THIa was used instead of THI, which also depends on the macrozone. These estimations coincide with those reported by dairy producers. Thus, the THI would be underestimating the decrease in milk yield due to heat stress. The lowest average economic losses per cow/season, 5 seasons average, occurred in macrozone VI (US$ 463.4), and the highest losses were observed in macrozone I (US $1161.4) both using THIa. Thus, losses at the country level fluctuate between US$ 29.0 and 108.4 million per season, depending on the index used. Finally, heat stress impacts negatively and significantly the Chilean dairy sector, which is highly dependent on the dairy production macrozone.