Sequential carry-over effects of corn particle size in brooding phase and feed form in growing phase on full-cycle...

This study evaluated the sequential carry-over effects of corn particle size during wk 1-6 and feed form during wk 7-15 on productive performance, egg quality, nutrient digestibility, and digestive organ development in Lohmann Brown laying hens from hatch to 80 wk of age. A sequential, phase-specific single-factor design was adopted, where the two factors (corn particle size and feed form) were tested sequentially in different rearing phases rather than simultaneously-this design was based on practical feeding practices in China's commercial layer industry and represented the core novelty of the study. The specific design is clarified as follows: In Phase 1 (wk 1-6), 1,980 one-day-old chicks were assigned to 3 treatments in a completely randomized design, with corn ground through 1, 4, or 6 mm screens. All diets were steam-pelleted and crumbled (20 replicates/treatment, 33 birds per replicate). In Phase 2 (wk 7-15), corn particle size was standardized to 4 mm for all treatment groups, and birds were further subdivided within each original particle size group to receive either mash or crumble feed, forming 6 treatment combinations (10 replicates per treatment, 31 birds per replicate). From wk 16-80, all birds received a common commercial mash diet to assess residual effects of early-life treatments. Compared with birds fed diets with corn ground through 6 mm screen, those fed 1 or 4 mm screen-ground corn during wk 1-6 had greater (P< 0.05) feed intake (FI) and body weight gain (BWG) at 3 wk, higher digesta transit rate, dry matter (DM) digestibility, and apparent metabolizable energy (AME) at 6 wk, and lower overall mortality (P< 0.05). It also improved feed conversion ratio (FCR) and total egg weight (P< 0.05) during the laying period (wk 18-80). Compared with mash feeding, feeding crumble during wk 7-15 increased (P< 0.05) FI and BWG at 15 wk, but decreased egg production rate and total egg weight (P< 0.05) during the laying phase (wk 18-80), with no effects on FCR or egg quality. These results indicate that the strategic feeding program-using 1 or 4 mm screen-ground corn with crumble feed during the brooding phase (wk 1-6), followed by mash feed with 4 mm screen-ground corn during the growing phase (wk 7-15) optimizes long-term laying performance in laying hens, with the benefits of early particle size and subsequent feed form acting independently rather than interactively.