A comparative study on the effects of dietary sunflower hulls on growth performance and digestive tract traits of broilers and pullets fed a pullet diet from 0 to 21 days of age

The effects of the inclusion of sunflower hulls (SFH) in the diet on growth performance, coefficient of total tract apparent retention (CTTAR) of nutrients, gastrointestinal tract (GIT) traits and short chain fatty acid (SCFA) concentration in the cecum were studied in chicks from 0 to 21 d of age. Treatments consisted in the combination of two chicken lines (female broilers vs. pullets) and two levels of SFH inclusion (0 vs. 30 g/kg). The control diet contained 11.94 MJ AMEn, 191 g crude protein, 9.8 g digestible Lys and 101 g neutral detergent fiber/kg. The experimental diet included 30 g SFH/kg at the expense (wt:wt) of the control diet. Growth performance was better (P < 0.001) in broilers than in pullets at all ages. Moisture content of the excreta was lower (P < 0.001) in pullets than in broilers at 21 d of age but an opposite effect was observed at 9 d. At 9 d of age, nutrient retention (P < 0.001) and AMEn of the diet (P < 0.01) were higher in broilers than in pullets but at 21 d of age the only difference detected was for N retention (P < 0.001). In absolute terms (g or cm) broilers had heavier (P < 0.001) digestive organs and longer small intestine (SI) and cecum than pullets. In relative terms, however, the GIT (P = 0.062), proventriculus (P < 0.001), gizzard (P < 0.001) and pancreas (P < 0.01) were heavier at 21 d, and the SI and the cecum were longer (P < 0.001) at both ages in pullets. SFH inclusion did not affect growth performance or organ weights at any age but increased the absolute length of the SI and cecum and the AMEn of the diet at 21 d of age (P < 0.05). At 21 d of age, fiber inclusion reduced moisture content of the excreta in broilers but no effects were observed in pullets (P < 0.05 for interaction). The pH of the GIT and the concentration of SCFA in the cecum were not affected by chicken line or SFH inclusion. Villus height and crypt depth were higher (P < 0.001) in broilers than in pullets but were not affected by SFH inclusion. In summary, broilers showed greater growth performance and nutrient retention at 9 d of age and better ileum absorptive capacity at 21 d than pullets. The dilution of the diet with 30 g SFH/kg did not affect chick performance and in fact, improved the AMEn of the diet in both chicken lines at 21 d of age.