Assessment of the Possibility of Reducing the Thermal Load in the Barn by using Mechanical Ventilation

The aim of this work is to evaluate possibility of reducing the heat stress of milking cows via climatic indices and the influence of air flow velocity in the object with milking cows using the cross-section method. For the purposes of evaluation, there was selected a four-row housing facility for 160 milking cows with natural ventilation; for the summer period, natural ventilation was supplemented with mechanical ventilation (2877 m³·h⁻¹ per cow). Measurements were conducted in the network created with 12 measuring points across the barn width, repeated in five cross-sections A, B, C, D and E, followed by further measurements in the longitudinal direction performed always in a row of 22 points placed in resting zones along the air flow direction. Considering the state of potentially high heat load with THI >78, it was observed that, according to ETIC, without employing the fans, ETIC in AOZ was higher than nAOZ, ETIC_AOZ = 25.34 ±0.42 vs ETIC_nOAZ = 24.51 ±0.44 (p <0.05). After activation of fans above lying area, ETIC in AOZ was lower than nAOZ, ETIC_AOZ = 23.40 ±0.61 vs ETIC_nAOZ = 23.68 ±0.60, which was not validated in evaluation of THI. Even though the limiting value of very high heat stress ETIC = 25 was not exceeded after activation of fans, decreasing of heat stress in rest zones did not reach recommended value ETIC = 20. A more significant improvement was validated in ETIC evaluation with measurements in longitudinal direction in the lying area – there was confirmed dominant influence of air flow speed. Heat load decreasing was influenced by speed and distribution of air in AOZ, both overall and local air exchanges in AOZ with ACH_v >100 h⁻¹, and barn length.