Commercial broiler birds may not spend enough time in the dark. At least 4 hours of darkness a day should be provideed for the best performance. As part of the virtual poultry welfare certifiaction course held by the Pennsylvania State University's College of Agricultural Sciences. Association professor in the department of animal and poultry science at the University of Saskatchewan spoke about research surrounding the relationship between daylength and bird welfare.
The conventional thinking in broiler production is that maximiziing daylength maximizes time birds can eat and therefore grow. New research shows birds need daily, sustained darkness to be healthy and grow.
The research is based on testing the theory that more light equals more weight gain. To test it, multiple trials were conducted with different lighting programs comprising.
14 hours of light, 10 hours of darkness
17 hours of light, 7 hours of darkness
20 hours of light, 4 hours of darkness
23 hours of light, 1 hour of darkness
After analyzed the results of a study comparing performance in terms of total body weight. That trial showed the 23 hours of light, 1 hour of darkness program was the least effective in terms of weight gain. At 32 days of age there was a slight difference in average broiler body weight between those programs but at days 39 and 49 the difference was more pronounced.
That same trial found adding darkness shifts the time when birds gain weight to later in their lives. This is important because if birds gain weight too quickly too early in their lives, they put undue stress on their metabolic and skeletal system. Darkness helps fortify the birds before their period of the greatest weight gain and allows them to gain more weight.
The same study examined numerous health conditions that affect birds health, welfare and ultimately performance. In general, these studies concluded more darkness meant fewer health problems.
