Withdrawal or reduction of the dietary vitamin premix on bone parameters of broiler chickens in two rearing systems
This study was conducted to compare the withdrawal or reduction of the vitamin premix (VP) from broiler diets at between days 29 and 42 of age on the characteristics of leg bones of the broilers in a battery cage (Trial 1) and a floor (Trial 2) rearing system. Seven experimental diets were formulated, based on wheat and barley, and consisted of four replicates per treatment. The metatarsus bone was used for measuring biomechanical bone characteristics, and alkaline phosphatase (ALP) activity and calcium concentrations blood serum to assess vitamin D3 status. The results of the first trial showed that there were no significant differences in body weight, strength of metatarsus bone and contents of ash, Ca and P in the toe with reduction or withdrawal of the vitamin premix from the diets during days 29 - 35. However, after 36 - 42 days there were significant differences for these parameters between the treatment without the vitamin premix (T1) and the other treatments. At 29 - 35 days and 36 - 42 days there were significant differences for ALP activity between T1 and the other treatments. The results of Trial 2 showed that the reduction in the vitamin premix and withdrawal at d 29 did not impair body weight, bone parameters and blood concentrations during the final growth period of the broilers. Finally, the results of the present study indicate that in the battery cage system it is possible to reduce the level of the dietary vitamin premix during the finisher period, but withdrawal can negatively affect body weight and bone parameters of broiler chickens, while in the floor system it is possible to withdrawal VP from broilers’ finisher diets.
Keywords: Alkaline phosphatase, ash, broilers, calcium, bone strength