Effects of calcium, phosphorus and zinc in wheat-based diets on broiler chickens' performance, immunity and bone parameters.

An experiment was conducted to investigate the effect of zinc (Zn) supplementation and different concentrations of calcium (Ca) and phosphorus (P) in wheat-based diets on the performance, immune responses and bone parameters of broiler chickens. A randomized complete block design with factorial arrangement was used (three concentrations of Zn supplementation×two concentrations of dietary Ca-P), 300 day-old broilers were assigned to six dietary treatments with five replicates of ten birds. Dietary treatments were the basal diet (control; TRT1), control plus 50 ppm Zn (TRT2), control plus 70 ppm Zn (TRT3), low Ca-P diet (0.60 to 0.30%; TRT4), low Ca-P diet plus 50 ppm Zn (TRT5) and low Ca-P diet plus 50 ppm Zn (TRT6). Ca and P in the control diet were 0.90 and 0.45% in the grower phase and 0.85 and 0.42% in the finisher phase. Changes in dietary Ca-P had no effect on body weight gain (BWG), feed intake (FI), feed conversion ratio (FCR) or serum Ca and P concentrations (P>0.05) whereas Zn supplementation increased FI (P 0.05). The lowest blood heterophil (H) and the highest lymphocyte (L) percentages and lowest H:L ratio were observed in birds fed with the diet containing a standard Ca-P with 70 ppm Zn supplementation (P 0.05). Tibia and fibula ash decreased by feeding lower Ca-P than the standard diet (P<0.05). It is concluded that low Ca-P diets did not have a detrimental effect on performance or blood and bone parameters and that Zn supplementation did not improve those parameters when feed was low in Ca-P.