The Effect of Lighting Intensity on Activity and Tonic Immobility Response of Broiler Chickens (Gallus gallus domesticus).

摘要

In commercial broiler production bird behavioral activity is regulated by lighting manipulations, and dim lighting is often used to reduce activity in order to promote growth. Broilers are more active under brighter lighting, and increased activity can promote improved skin and skeletal health. However, it has been suggested that birds reared under brighter lighting conditions may be more fearful, which can lead to injury and death if birds pile after being startled. I aimed to assess the relationship between fear response and light intensity, and to determine whether behavioral rhythms could be entrained at moderate light levels. Cobb x Cobb broilers (N = 273) were reared under either a 20 lux or 10 lux photophase, with a 0.5 lux scotophase and a 12L:12D photoperiod. Activity was measured continuously for 48 hours on days 22--24 and 31--33 of age using a passive infrared detection system. Tonic immobility (TI) fear responses were measured at 26--30 days of age, with half of the birds tested just after the dawn transition and half just after the dusk transition, the times when minimal and maximal responses should occur. The 20 lux treatment group was more active during the photophase than the scotophase, and also had a significant difference in TI responses between these time periods, indicating the presence of an activity rhythm as well as a TI rhythm. In contrast, 10 lux birds only showed a non-significant trend towards a photophase-scotophase activity difference, and no TI rhythm. The 20 lux birds were more active overall than the 10 lux birds, and also had a longer TI latency to turn their heads, required a greater number of inductions and tended to have longer latencies to right, than 10 lux. My results indicate that 20 lux was sufficient to entrain behavioral rhythms and promoted more activity than 10 lux, but was also associated with increased fear responses as measured by the TI test.