ABSTRACT
The threshold for heat stress on milk yield of Holstein
crossbreds under climatic conditions in Thailand
was investigated, and genetic effects of heat stress
on milk yield were estimated. Data included 400,738
test-day milk yield records for the first 3 parities from
25,609 Thai crossbred Holsteins between 1990 and
2008. Mean test-day milk yield ranged from 12.6 kg
for cows with