p Ghasemi - Department of Animal Science, Khorasgan (Isfahan) Branch, Islamic Azad University, Isfahan, Iran
m Toghyani - Department of Animal Science, Khorasgan (Isfahan) Branch, Islamic Azad University, Isfahan, Iran
a.a Gheisari - Isfahan Agricultural and Natural Resources Research Center, Isfahan, Iran

As an analog of vitamin D, 1alpha-hydroxycholecalciferol (1α-OH-D3) has been demonstrated to improve the performance and phosphorus utilization of broilers (Snow et al., 2004). 1α-OH-D3 couldreplace vitamin D3 in chicken diets and the activity of this form is about 8 times of vitamin D3 basedon tibia ash (Edwards et al., 2002).When fed to broilers at 5 μg/kg, 1α-OH-D3 has been shown to reduce the incidence of tibial dyschondroplasia and improve phytate P utilization (Edwards et al., 2002). The objective of this study was to evaluate growth performance and tibial dyschondroplasiaincidence in broiler chicks when 1α-OH-D3 substitute as vitamin D3 in diet. Materials and methods A total of 210 one-day-old Ross 308 broiler chicks were randomly assigned to 15 floor penscontaining 14 chicks each based on a completely randomized design. The three dietary treatmentsconsisted of: A (control: basal diet with vitamin D3), B (basal diet with vitamin D3 and 5 μg/kg of 1α- OH-D3) and C (basal diet with 5 μg/kg of 1α-OH-D3 without vitamin D3). Broilers received dietary treatments from 1 to 42 d in three phases: starter (1-14 d), grower (14-28 d) and finisher (28-42 d).Performance parameters (feed consumption, body weight gain and feed conversion ratio) were measured in different periods and overall growth period. Tibial dyschondroplasia incidence wasdetermined at 42 d. Results and discussion The feed intake of broilers in overall growth period (1 to 42 d) in treatment B were significantly increased (P< 0.05). The highest body weight at 42 d was observed in treatment B (P< 0.05). Dietarytreatment had not significant effect on feed conversion ratio but it tended to decrease in treatment B. Incidence of tibial dyschonroplasia were significantly increased in broilers received dietary treatment C (P< 0.05). Adding 1α-OH-D3 to broiler diet improved growth performance, however 1α-OH-D3 at level of 5 μg/kg without vitamin D3 could not prevent from incidence of tibial dyschondroplasia. Researchers suggest that 1α-OH D3 might improve the growth of broilers by increasing phytate phosphorus utilization (Han et al., 2009).

Broiler, vitamin D3, 1-alpha hydroxycholecalciferol, Performance, Tibial dyschondroplasia