Using publicly available weather station data to investigate the effects of heat stress on milk production traits in Canadian Holstein cattle

Abstract

Heat stress imposes a challenge to the dairy industry, even in northern latitudes. In this study, publicly available weather station data was combined with test-day records for milk, fat, and protein yields to identify the temperature-humidity index (THI) thresholds at which heat load starts affecting milk production traits in Canadian Holstein cows. Production loss per THI unit above the threshold for each trait was estimated. Test-day records from 2010-2019 from 166,749 cows raised in Ontario and from 221,214 cows raised in Quebec were analyzed. Annual economic losses due to heat stress were estimated from the average losses of fat and protein yields based on the annual average of 156 days with THI exceeding the calculated thresholds. Average thresholds for the daily maximum (THI_max) and daily average (THI_avg) THI estimated across lactations in both provinces were THI_max (THI_avg) 68 (64), 57 (50), and 60 (58) for milk, fat, and protein yield, respectively, indicating that milk components are more sensitive to heat stress. An economic loss of about $34.5 million per year was estimated. Our findings contribute to an initial investigation into the impact of heat stress on the Canadian dairy industry and provides a basis for genetic studies on heat tolerance.

Estimation of Genetic Parameters of Heat Tolerance for Production Traits in Canadian Holsteins Cattle

“…After merging production and weather records, the final data set contained 1.3 million TD records for the three production traits from 198,292 first-lactation cows in 1132 herds. The descriptive statistics for milk, fat and protein yields over the 10-year period below and above the THI threshold of each trait based on Campos et al [ 20 ] are reported in Table 1 . The adjusted means for all three traits for each THI value can be seen in the figures 3 to 5 in Campos et al [ 20 ].…”

“…The descriptive statistics for milk, fat and protein yields over the 10-year period below and above the THI threshold of each trait based on Campos et al [ 20 ] are reported in Table 1 . The adjusted means for all three traits for each THI value can be seen in the figures 3 to 5 in Campos et al [ 20 ].…”

“…This index can then be associated with production records, such as test-day (TD) records, to investigate the relationship between cow performance and heat stress using data from several farms over several years [ 15 , 16 , 17 ]. In Canada, studies on dairy cattle have focused on understanding the impact of heat stress on milk production and have shown a considerable negative impact on the Canadian dairy industry [ 18 , 19 , 20 ], highlighting the need to implement measures to mitigate heat stress.…”

“…To the best of our knowledge, the genetic parameters of production traits considering heat stress have not yet been estimated in Canadian dairy cattle. In an initial study using Canadian Holstein dairy cows from two major dairy producing provinces (i.e., Quebec and Ontario) THI thresholds for milk production traits were determined [ 20 ]. Using the pre-determined thresholds, the objectives of this study were to estimate the genetic parameters for heat tolerance for milk, fat, and protein yields in Canadian Holsteins and to assess the potential presence of GxE interaction when accounting for heat tolerance in the genetic evaluation model.…”

Relationship of Meteorological Data with Heat Stress Effect on Dairy Cows of Smallholder Farmers

“…Weather station collected environmental parameter records such as temperature, humidity, and other climate-related measurements (e.g., wind speed, dew point, etc.) hourly, provide continuous data over years [10]. These data could be used for calculating the THI which in turn would be useful to assess heat stress effects on dairy farms.…”