Original: Article from the Poultry Times WeChat Official Account

To maximize feed intake and growth rate during their short lifespan, broiler chickens have traditionally been raised under long light cyle (photoperiods) and short dark cycle (scotoperiods).

This practice has had many adverse effects on animal welfare. The EU legislation now stipulates that, except for the first 7 days of life and the last 3 days before slaughter, the lighting for broiler chickens must follow a 24-hour cycle.

Including a total of at least 6 hours of darkness, among which there should be at least one continuous period of no less than 4 hours of darkness, excluding the transitional dimming period(EC Council Directive 2007/43/EC).

However, in many countries around the world, the practice of providing a light cycle of 23 hours or more per day is still widely adopted.

The adverse effects of prolonged lighting include an increase in the mortality rate and the rate of lameness among chickens.

Recent research in Canada has shown that the light cycle (ranging from 14 to 23 hours) has a linear relationship with mortality rates and lameness.

The long light cycle also causes the size of the eyeball to increase. The reason for this is that the normal circadian rhythm of eye growth is disrupted.

Paradoxically, by extending the period of darkness to slow down the growth of broiler chickens, considering the losses caused by death and diseases, the overall production efficiency might actually increase.

During the dark period, chickens can continue to rest and sleep, and the secretion of melatonin increases, which is beneficial for the body's recovery.

More pronounced circadian rhythms can improve leg health and overall activity levels.

If the dark period lasts for at least 4 hours, the impact of light intensity on the behavior and welfare of broiler chickens may be greater than that of further extending the dark period.

There is no reason to stipulate that the mandatory 6-hour dark period in the EU must be continuous.

During the first few weeks of life, the chicks raised by hens often go out to forage and explore frequently, and then briefly return to rest under the hen's body.

The broiler chicken industry is increasingly focusing on simulating this pattern by setting multiple standardized dark periods within every 24 hours, totaling 6 hours.

The effectiveness of this intermittent lighting scheme has not yet been fully evaluated.