Abstract
Purpose :
To study dairy cows’ ability to negotiate an obstacle course under different lighting conditions.
Methods :
In a change-over study, 12 non-lactating dairy cows were encouraged to pass through obstacle courses 14.5 m long x 3.8 m wide in a window-less room under 14 different lighting conditions ranging from non-measurable to 2.9 µmol/m2/s (43 cd/m2) and including white or red lights with each obstacle course either uniformly or non-uniformly illuminated. Lighting properties, including illuminance (lux), photon flux density and light spectrum (µmol/m2/s/nm), spectral photon radiance (log photons/m2/s/nm), and illuminance uniformity, and assessment of the environmental light field (ELF) were used to describe each lighting condition from both a bovine and human perspective. Data were analyzed in a generalized mixed model to test if the lighting condition affected speed and stride rate. Additionally, ethograms constructed from behavior observations with a thermal imaging camera were analyzed.
Results :
The lighting condition affected cows’ average speed (P=0.006) and stride rate (P=0.014). Pairwise post hoc comparisons showed that nonmeasurable light (darkness) did not alter cows’ speed or stride rate. Instead, cows spent a longer time in the obstacle course and walked slower in red, non-uniformly spread light of medium intensity compared to white, evenly distributed light of two higher intensities (p=0.01 for both) and red, uniformly distributed light of two lower intensities (p=0.001 and p=0.02, respectively). Ethograms did not reveal obvious differences in behavior or ability to avoid obstacles regardless of lighting conditions.
Conclusions :
Cows performed equally well when the luminance was in the scotopic range for human observers and perceived as dark under mesopic and photopic conditions. However, non-uniform illumination of the obstacle course with medium bright, red light (where the luminance varied from scotopic to low photopic for a human observer in different parts of the course) made cows move slower. Neither dimmer nor brighter uniformly spread red or white lights caused this effect. Hence, cows do not necessarily need artificial light in a barn at nighttime, but both dim red and white lights seem cow friendly. A uniform illumination, where shady areas and large shadows are avoided, is likely to be preferred.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.