Effects of Feed Physical Form and Insoluble Fiber during Different Rearing Periods on Productive Performance, Immune Response, Behavior, Tibia indices and Gastrointestinal Alterations of W-36 Laying Pullets

This experiment was conducted to evaluate the effects of changing feed form in commercial laying pullets at their 9-14 weeks of age. In the first eight weeks of rearing, the birds were fed four basal diets, including two feed forms (mash;M vs. pellet;P) and two levels of sunflower hulls (SH)  inclusion (0 vs. 4%); then, they were assigned to 11 treatments with eight replicates of 9 birds each. The experimental groups consisted of the mash diet during 0-8 and 9-14 weeks (control); mash from 0-8 week and pellet +SH from 9-14 weeks (M-PSH); and so on MSH-MSH; MSH-PSH; P-P; P-M; P-MSH; P-PSH; PSH-PSH; PSH-MSH; and M-MSH. During the whole period, average daily feed intake (ADFI) in the birds fed with pellet or mash and then fed with the pellet containing SH (P-PSH and M-PSH) was higher than with the other treatments (P < 0.05). Average daily weight gain (ADG) was affected by dietary fiber and feed form, whereas it was found lower in the PSH–MSH treatment birds and greater for the birds in MSH-PSH treatment than others (P < 0.05). Further, FCR improved in the birds fed the mash diet with and without fiber from  during 1-14 weeks (P < 0.05). Feeding pellet diet without fiber during 1-14 weeks resulted in lower gizzard weight and deeper crypt than the other groups (P < 0.05). In addition, the greater and lower villus surface area belonged to the birds fed MSH-MSHP-P diets during 1-14 weeks, respectively. The greatest tibiotarsal index was related to the group fed the pellet or mash without fiber during 0-14 weeks (P < 0.05). In conclusion, considering the costs for pellet production, it seems that feeding pellets just during the first eight weeks of age could lead to better performance in commercial situations. Moreover, dietary  inclusion of SH improved the function of gizzard.