Effects of Low Crude Protein and High-Fiber Diets on Production Performance, Egg Quality, Behavior, and Integument Condition in Laying Hens

Low crude protein (LCP) diets supplemented with essential amino acids may reduce the environmental impact of poultry production, whereas high-fiber diets containing increased insoluble non-starch polysaccharides (iNSP) may improve hen welfare by reducing feather and injurious pecking. To investigate the effects of these dietary strategies on laying hens, a total of 1,600 sixteen-week-old Bovans Robust White hens were randomly assigned to 16 pens and fed experimental diets from 16 to 50 weeks of age in a 2 × 2 factorial arrangement with two crude protein levels (standard, SCP; low, LCP) and two iNSP levels (standard fiber, SF; high fiber, HF). The LCP diets contained 1.5% units less crude protein, and HF diets contained 2% units more iNSP (via oat hull inclusion) than their respective standard diets. All diets were formulated to contain similar levels of digestible amino acids. Feed intake, egg production, mortality, egg quality, and integument condition were recorded. Fearfulness was assessed through a novel object test, and pecking behavior was evaluated by direct observation. Data were analyzed using linear mixed-effects models in R. Feed intake was significantly lower in the HF group than the SF group from 32 to 43 weeks of age (P < 0.001). Fiber level did not affect body weight at 34 weeks of age; however, at 49 weeks, hens in the HF group had higher body weight than those in the SF group (P = 0.003). Hens fed HF diets exhibited improved feather cover (P = 0.016), fewer rear body injuries (P = 0.012), higher egg weight (P = 0.010), and increased egg mass (P = 0.011) compared to hens fed SF diets. LCP diets resulted in lower egg weight (P = 0.015) and higher yolk color (P < 0.001) than SCP diets. Dietary treatments did not affect lay percentage, mortality, novel object responses, eggshell thickness, eggshell weight, yolk weight, or albumen dry matter. In conclusion, LCP diets supplemented with essential amino acids maintained lay percentage, and HF diets improved plumage condition and reduced rear body pecking injuries among laying hens.