Zoo-hygienic assessment of lighting in semi-open freestall barns for dairy cows

Abstract

Abstract. The aim of the present study was to perform a zoo-hygienic assessment of lighting (natural and artificial) in different technological zones (stalls, manure and feed alleys) in semi-open freestall barns for dairy cows. The survey was conducted over a period of one year in 3 production buildings from 3 cattle farms located in three different areas of Southern Bulgaria - Stara Zagora District, Haskovo District and Plovdiv District. The building’s parameters were as follows: building No.1 - capacity 120 cows, 60.00/18.00/3.00m, 1080m2; building No.2 - capacity 120 cows, 66.00/18.00/3.00m, 1188m2 and building No.3 - capacity 500 cows, 90.00/45.00/3.30m, 4050m2. The premises lighting was measured with two combined apparatuses (Lutron EM-9300SD, 0-20000 lux and PU 150, 0-100000 lux), twice a month at 10.00, 12.00, 14.00, 16.00 and 18.00h at a height of 1m from the floor of the three technology zones. Summarized for all buildings, the light level varies widely by buildings, by seasons, by hours of reporting and by technological zones with limit values between 1 and 9810 lux. In all barns the most intense was the light above the feed alleys, followed by stalls and manure alleys; by hours of reporting during the day the level of lighting above the three technological zones was higher at midday (12.00-14.00h) compared to morning (10.00h) and afternoon (18.00h). Buildings No.1 and No.2 with a smaller built-up area provide more intensive lighting over all technological zones throughout all seasons compared to building No.3 with bigger built-up area: from 7.34 to 13.8 times over stalls, from 3.22 to 5.62 times over manure alleys and from 2.79 to 8.00 times over feed alleys. In buildings No.1 and No.2 there were prerequisites at least 16 hours of day light (photoperiod) to be provided during summer, autumn and spring, while in the winter months up to 8.00am and after 6.00pm the used artificial lighting was with low intensity and cannot provide the recommended over 160 lux intensity of the light. In building No.3 during most of the day for all seasons, the level of lighting above stalls and manure alley where the animals stay the longest time, the lighting level was lower than 160 lux. The factors ‘building’, ‘season’ and ‘hour of the day’ had a statistically significant effect (P<0.05-0.001) on the level of lighting in the three technological zones in the studied buildings. Of the associated factors, only the combination ‘season*hour of reporting’ had no significant effect on the lighting in the zones above the stalls and manure alleys.