Improving Eggshell Strength and Bird Welfare with Interrupted Dark Period
Introducing alternative lighting strategies that provide hens with additional feeding opportunities during scotophase, or dark periods, can significantly enhance egg quality and bird welfare. Research by Alexis Clark, a graduate student at Clemson University, presented at the 2024 International Poultry Scientific Forum, suggests that interrupting dark periods can improve eggshell-breaking strength, thickness, and weight while maintaining bone health.
Enhancing Eggshell Formation During Scotophase
Clark’s research highlights that most eggshell formation occurs during the scotophase when hens are not feeding and lack available calcium in their digestive tract. “During late lay, it’s common to see eggs with poor eggshell strength and birds with increased bone-health issues,” Clark explains.
By altering lighting strategies to break up dark periods with nighttime feeding, hens have the chance to replenish calcium. This adjustment has been shown to reduce issues with eggshell quality and bone fractures, addressing a significant economic concern for the poultry industry, which can suffer up to a 20% profit loss due to these problems.
The Drawbacks of Conventional Lighting Systems
Typically, laying hens in commercial systems receive 16 hours of continuous light followed by 8 hours of darkness during their laying period. The egg-laying cycle spans 24 hours, with eggshell formation mainly occurring over a 20-hour period at night when hens are not consuming food.
“This poses a challenge because the gastrointestinal tract empties after about 4 hours of darkness,” says Clark. An empty digestive tract is detrimental for hens during eggshell calcification, impacting both egg quality and animal welfare. Without calcium from their digesta, hens must rely on their bones for calcium, leading to progressive bone resorption and an increased risk of fractures and osteoporosis.
Exploring Alternative Lighting Strategies
To tackle this issue, Clark and her colleagues conducted a trial to assess the impact of interrupting the dark period on hen performance, welfare, and egg quality. “Balancing these elements is crucial,” Clark notes. “High-quality eggs are in demand, but meeting this demand requires high-quality birds.”
The study involved 240 Hy-line W36, 17-week-old pullets housed in 12 pens with 20 hens per pen. The control group followed a standard lighting schedule of 16 hours of light and 8 hours of darkness daily. The test group experienced an interrupted scotophase schedule: 15 hours of light, 4 hours of darkness, 1 hour of light, and then 4 hours of darkness.
The researchers monitored egg production, feed intake, and collected eggs to evaluate internal and external quality parameters over three days during week 50. They also assessed welfare measures using a 0-to-2 scale.
Promising Results
The study found no significant differences in average daily feed intake, egg weight, albumen weight, Haugh unit, or yolk color between the groups. However, eggshells in the test group exhibited significantly higher breaking strength (33.6N compared to 27.22N), greater thickness (0.63 mm versus 0.39 mm), and higher weight (5.71 g versus 0.35 g) than those in the control group.
No significant differences were observed in physical welfare measures, including scores for keel bone damage, footpad dermatitis, feather damage, and comb and skin lesions.
“Since calcium requirements are highest during scotophase, our approach aimed to increase calcium replenishment opportunities during this period rather than increasing dietary calcium or the length of the dark phase,” Clark explains. “Our hypothesis was confirmed: interrupting scotophase produces higher quality eggs without affecting hen performance or welfare.”
Economic and Practical Implications
Clark emphasizes the substantial economic and practical implications of these findings. “Increasing light hours has been linked to higher feed intake, which is not cost-effective for producers,” she says. “A lighting strategy that allows hens to replenish calcium during the daily scotophase without extending overall light hours or increasing feed intake shows promise as a viable solution.”
Overall, this research suggests that interrupting dark periods can significantly enhance eggshell quality and bird welfare without negatively impacting feed intake or overall performance, offering a potential solution to an ongoing issue in the poultry industry.
