D. Dimov1*, Tch. Miteva1, I. Marinov2, Zh. Gergovska2, Т. Penev1, A. Enchev3

1Department of Applied Ecology and Animal Hygiene, Faculty of Agriculture, Trakia University, 6000 Stara Zagora, Bulgaria 2Department of Animal Science – Ruminants and Dairy Farming, Faculty of Agriculture, Trakia University, 6000 Stara Zagora, Bulgaria 3Enfo Agro LTD, Bulgaria

(Manuscript received 2 December 2016; accepted for publication 16 February 2017)

Abstract. The study was conducted in three semi open free-stall barns (B1, B2, and B3) for dairy cows with capacities for 120, 120 and 500 cows, respectively, from three different dairy farms (F-1, F-2 and F-3), situated in Central Southern Bulgaria. The investigated farms had the same production system – loose housing in semi open free-stall dairy barn. For each of the farms the main microclimatic parameters – air temperature, relative humidity and speed of airflow were recorded twice a month at 10.00 h 12.00 h, 14.00 h, 16.00 h and 18.00 h of the day inside the barns in three main technological zones – above the stalls, above manure and feed alleys and outside the buildings. It was found that: a) Microclimatic parameters (air temperature, air relative humidity and speed of airflow) in technological zones (above the stalls, the manure and feed alleys) of three semi open free-stall dairy barns meet the animal hygienic requirements for all seasons according to Regulation No. 44 (2006). Exceptions are some values of relative humidity in B1 and B2 in the spring, and in B1 in winter and summer, which are lower than the minimum humidity (50%) according to the standard. b) The investigated barns are characterized with poor insulation and do not provide enough isolation from the external ambient temperatures. With the exception of winter, the temperature of the air inside the buildings was lower than that outside, with minor differences for all seasons. The fans in the barns have no effect on the inside air temperature, especially in summer. There was a risk of higher temperatures mainly during the summer period. c) There is no significant difference between the average temperatures, air humidity and speed of airflow in all technological zones of the investigated barns. d) The largest and statistically significant is the difference between the relative air humidity outside and inside the building in Farm 3, followed by buildings in Farm 1 and 2, where the differences are smaller and statistically insignificant. e) Factor analysis revealed a significant effect: of the farm on temperature in the different technological zones in the barns (P <0.05-0.01); of the farm in the zones of manure and feed alleys (P <0.001) and less effect in the zone of stalls (P <0.05) on speed of airflow, the factor season on speed of airflow in all zones (P <0.001), the time of recording in the zone of manure alley on speed of airflow (P <0.05); the farm, season and time of recording on the humidity in the three technological zones (P <0.001).