Application of a tunnel-ventilated barn on the physiological responses, milk yield, and dry matter intake of dairy cows in tropical area during the wet season

Dairy cows often experience heat stress in the tropics. Tunnel ventilation technology reduces heat stress in dairy cow housing. Here, we examined the performance of tunnel-ventilated barns on the physiological responses, milk yield, and dry matter intake of dairy cows during the wet season in a tropical area. The experiment was conducted on a commercial dairy farm in Malang, Indonesia from mid December 2017 until mid January 2018. Lactating Friesian Holstein cows (n = 661) were studied in two barns of different dimension, with cooling treatments. Air temperature, relative humidity, and air speed were measured. Respiration rate, lying down percentage, milk yield, and dry matter intake were analyzed in response to modified environmental conditions. Data were analyzed with independent sample t tests using SPSS® Statistics 24 for Windows. Outisde and inside air speeds for both barns (P < 0.05) showed significant difference. Surprisingly, no differences were found for temperature (T), relative humidity (RH), and temperature–humidity index (THI) between the outside and inside for both barns (P > 0.05). A significant difference was noted in milk yield, dry matter intake (DMI), respiration rate (RR), and lying down percentage (LDP) (P < 0.05). Thus, the tunnel-ventilated barn performed better and air speed was better distributed inside the barn. However, the barn had environmental conditions similar to those outside. Dairy cows showed high RR as milk yield and DMI increased. In the future, lying down behavior of dairy cows in response to cooling treatments in the tropics needs to be further studied.