Gorgan University of Agricultural Sciences and Natural Resources Poultry Science Journal 2345-6604 14 1 2026 01 01 Performance, Body Weight Uniformity, Feather Pecking Behavior, Bone Quality, and Intestinal Histomorphology in Pullets Fed Mash or Pelleted Diets at Different Rearing Stages 117 130 7585 10.22069/psj.2025.23419.2280 EN Mohammad Sedghi Department of Animal Sciences, College of Agriculture, Isfahan University of Technology, Isfahan, Iran, 84156-83111. Mohsen Moaiedi Department of Animal Sciences, College of Agriculture, Isfahan University of Technology, Isfahan, Iran, 84156-83111. Farzad Hashemzadeh Department of Animal Sciences, College of Agriculture, Isfahan University of Technology, Isfahan, Iran, 84156-83111. Majid Olyayee Department of Animal Science, Faculty of Agriculture, University of Tabriz, Tabriz, Iran, 5166616471. Journal Article 2025 03 09 Feed form affects the physiology of the gastrointestinal tract of pullets, but the optimum time of pelleted diet feeding during the rearing period should be determined to achieve optimum performance. This experiment evaluated the effects of feed form (mash or pelleted) on pullets' productive performance when fed during different rearing periods. Five treatments included: feeding a mash diet from hatching to 14 wk (MA14), feeding a pelleted diet from hatching and shifting to the mash diet at the end of the 4^th (PE4), 8^th (PE8), and 12^th (PE12) wk, and feeding a pelleted diet from hatching to the 14th wk (PE14). Results showed that the average daily feed intake (ADFI) and average daily gain (ADG) increased linearly with increasing pelleted feeding time from 0 to 14 weeks (p < <em>0.01</em>). Pullets shifted from a pelleted to a mash diet at any age had a poorer overall FCR than those fed either diet continuously (<em>p</em>< 0.05). The gizzard weight was linearly decreased by increasing the pelleted diet feeding time from 0 to 14 wk (<em>p<0.01</em>). The jejunal absorptive surface area was lower (<em>p<0.01</em>) in pullets fed PE4, PE8, and PE12 diets than in those fed the MA14 diet. In examining the relative weights of internal organs, tibia bone quality, and feather score, no significant differences were observed among the experimental treatments. The results showed that feeding pullets a pelleted diet throughout the rearing period increased ADFI and ADG but led to poor gizzard development. However, pullets that shifted from a pelleted to a mash diet at 4, 8, and 12 wk of age had a well-developed gizzard compared to those fed a pelleted diet continuously. https://psj.gau.ac.ir/article_7585_6f84bfbea0d307e6ff2d0bf069b16b60.pdf