Efficiency of heat reduction in barns during rainy season and barn characteristics: their relationship to reproductive performance of dairy cows in a tropical environment

Abstract

The objectives of this study were to evaluate the impact of efficiency of heat reduction on barns during the rainy
season and barn characteristics on the reproductive performance of dairy cows in a tropical environment. Data of cows
from 125 small-holder dairy farms in Chiang Mai, Thailand, during May to August 2014 was used. Reproductive
performance indices, e.g. days to first insemination (DI) and days open (DO), were used as dependent variables.
Microclimate factors included differences in temperature (TEMP_DIFF) and relative humidity (RH_DIFF) between the
inside and outside of barns. From the total of 5,255 lactation data, 27 and 1,398 data was excluded due to missing data
at the end of the follow-up for DI and DO models respectively. Results showed that both DI and DO were significantly
related to calving season, roof materials and some farm management factors, but only DO were related to TEMP_DIFF.
In conclusion, reproductive performance in the tropics is influenced by all factors related to climate. A decrease in
pregnacy rate is more influenced by heat stress especially a decrease in temperature within barns than estrus
expression.