Study on energy requirement of Wenshui Luhua Green-Shelled laying hens during the late laying period

The effects of dietary energy levels (DEL) on the late-laying performance, egg quality, and serum biochemical indices of Wenshui Luhua Green-Shelled laying hens are reported. A total of 1000 hens of 45 wk age were randomly allocated to five dietary treatment groups, each replicated five times, each containing 40 hens. Treatments included five levels of metabolizable energy (ME): ME1-5 (2500, 2590, 2695, 2790, and 2880 kcal/kg, respectively); all other nutrients were maintained at consistent levels. Following a 14-day adaptation period (wk 45-46), hens underwent a 42-day experimental phase (wk 47-52). Feeding, metabolic, and comparative slaughter trials were performed. A factorial design was used to develop a predictive model for ME requirements. Average daily feed intake, ME intake, egg production (EP) rate (%), egg weight, daily egg mass (EM, g/bird·d), and feed conversion ratio were affected by DEL (P < 0.01), but daily gain (DG, g/d), body weight (BW, kg), and metabolic body weight (BW^0.75, kg) were not (P > 0.05). The ME3 group exhibited the best overall performance, with higher EP and EM than other groups The maintenance ME requirement was 108.22 kcal/(kg^0.75·d); the ME requirement for weight gain (DG) (5.08 kcal/g) had an efficiency of 0.60, and that for EP (2.77 kcal/g) had an efficiency of 0.53. A predictive model for total daily ME requirement (kcal/d) was developed (ME requirement = 108.22 × BW^0.75 + 5.08 × DG + 2.77 × EM). These findings provide poultry producers with a precise model to optimize dietary energy formulation (recommended at ∼2695 kcal ME/kg) for Wenshui Luhua Green-Shelled hens during late lay, enhancing feed efficiency, egg output, and economic returns while avoiding the performance losses associated with sub- or supra-optimal energy levels.