| Abstract |
The THI based on ambient temperature and relative humidity, is commonly used as an indicator of heat stress in dairy cattle. However, wind speed is another environment variable result in convective cooling and could affect to the thermal balance ability of animal. For accuracy of breeding values on milk yield trait for heat tolerance prediction in Crossbred Thai Holstein cattle, addition of wind speed to THI equation was therefore evaluated. Data included 116,828 test-day milk yield records for first lactation from 14,485 cows between 1990 and 2012. Daily temperature, humidity and wind speed data from 14 provincial weather stations were used to calculate THI1 (conventional) and THI2 (+wind speed). Analyses were used repeatability model by REMLF90 and BULPF90. Threshold point of THI1 and THI2 were 75 (75-85 interval) versus 28 (28-38 interval), respectively. The heritability (h2) and genetic correlation (rg) were 0.09-0.14 and -0.21 (THI1), 0.17-0.20 and -0.11(THI2). Coefficient of determination (R2) of THI1 and THI2 were 0.979 and 0.986, respectively. In summary, even the conventional THI is commonly useful, adjustment wind speed to THI could improve more accurately estimation of milk yield of Cross-bred Thai Holstein cattle in Thailand. |
Publication
Journal Publication
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