Color temperature of light-emitting diode lighting matters for optimum growth and welfare of broiler chickens

Light-emitting diode (LED) light bulbs are becoming more prevalent in broiler production as they are dimmable and more energy efficient than compact fluorescent lamps. Although there is some research on how spectrum of light can affect production, little has been conducted on how it may affect stress, and behavior. To determine how different spectrum of light produced by LED lights could affect production, stress and behavior we raised broilers under either 2700 K (WARM) or 5000 K (COOL) color temperature LED bulbs. To determine stress susceptibility bilateral asymmetry (ASYM, n=128), plasma corticosterone concentrations (CORT, n=40) and heterophil/lymphocyte ratios (HL, n=80) were measured. Fear was measured using tonic immobility (TI, n=128), inversion (INV, n=128) and isolation (ISO, n=128). Weight gain and feed conversion ratio (FCR) were also determined. The COOL birds had lower ASYM (1.65 +/- 0.08mm, P=0.001), CORT (5.8 +/- 1.2 ng/dl, P=0.01) and HL (0.16 +/- 0.01, P=0.03) than the WARM birds (2.38 +/- 0.14mm, 13.4 +/- 2.7 ng/dl and 0.21 +/- 0.02, respectively). The COOL birds righted faster during TI (136.2 +/- 11.1 s, P=0.001), flapped less intensely during INV (4.1 +/- 0.1 flaps/s, P<0.001) and vocalized less during ISO (45.3 +/- 2.8 vocalizations, P=0.005) when compared with WARM birds (207.2 +/- 15.8 s, 4.9 +/- 0.1 flaps/s and 56.5 +/- 2.9 vocalizations). The COOL birds (2.89 +/- 0.03 kg, P=0.02) grew to a heavier weight at the end of 42 day then WARM birds (2.79 +/- 0.03 kg). The COOL birds (1.54 +/- 0.03) had better FCR (P=0.02) than WARM birds (1.61 +/- 0.01). These results demonstrate that raising broilers under 5000 K LED lights can reduce their stress, fear and increase weight gain when compared with 2700 K. These results indicate that the spectrum of light used for rearing of broilers is not only important for production, but also for welfare of the birds.