Effects of calcium and phosphorus levels on the performance, carcass characteristics and bone mineralization of broiler chickens
The study determined the effect of Calcium (Ca) and Phosphorus (P) levels on growth performance, carcass characteristics, tibia ash and serum Ca and P concentration of broiler chickens with a view to determining the optimum levels of these elements for growth and bone mineralisation. A total of three hundred and sixty day-old unsexed Arbor Acre broiler chicks were assigned to twelve dietary treatments in a 4×3 factorial design comprising of four Calcium (Ca) levels (0.6, 0.75, 0.9 and 1.2%) and threeAvailable Phosphorus (aP) levels (0.25, 0.35 and 0.45%). Each treatment group consisted of 30 birds and each treatment had three replicates of ten birds and the study lasted for eight weeks. Data were collected on the growth performance and carcass characteristics of the broiler chickens. Digestibility trials were also carried out from 4-6 weeks of age. Feed and feacal samples were analysed for proximate analysis. The right tibia of three birds per treatment were removed to determine the tibia parameters and blood samples were collected to determine serum Ca and P concentration. The birds fed 1.2% Ca: 0.45% aP had the highest (P<0.05) final body weight (1979 g/bird) and daily weight gain (46 g/bird), which were similar to those of birds fed 0.6% Ca and 0.35%aP and 1.2% Ca: 0.35% aP levels comparedto the other treatment groups. This same trend was observed for feed conversion ratio. The highest (P<0.05) daily feed intake was observed for birds on 1.2% Ca: 0.35% aP treatment group. The dressing weight increased as the Ca levels increased but Ca and aP levels had no significant effect on othercarcass portions.Birds fed 0.9% Ca and 0.35% aP had the highest (P<0.05) dressing percentage compared to other treatment groups.Ca and aP had no significant (P<0.05) effect on Tibia weight. Percentage tibia ash increased linearly with increasing Ca values. Birds fed 1.2% Ca and 0.45% aP had the highest (P<0.05)percentage ash value of 44.61%. However, birds fed 0.9% Ca and 0.35% aP had a comparable high percentage tibia ash. Tibia Ca content increased with Ca and aP levels and birds fed 1.2% Ca and 0.45% aP had the highest Ca content. Tibia P content increased linearly with increase in aP levels and birds fed 0.3% Ca and 0.45% aP had the highest tibia P content. Serum Ca increased with decrease in aP values and birds fed 0.75% Ca and 0.25% aP had the highest (P<0.05) serum Ca content of 20.00 mg/dL. There was a linear increase in serum P content with increase in aP values. Birds fed 0.6% Ca and 0.45% aP had the highest (P<0.05) serum P content of 12.62 mg/dL. Ca and aP had a significant (P<0.05) effect on the apparent digestibility coefficient of crude protein. Birds fed 0.75% ca and 0.35% aP (T5) had the highest value of 83.85%. The apparent digestibility coefficient of Ash increased linearly with increase in Ca values. Birds fed 1.2% Ca and 0.35% aP had the (P<0.05) highest Ash value of 65.62%. Ca and aP had no significant (P<0.05) effect on dry matter, ether extract, crude fibre and nitrogen free extract. The study concluded that the calcium and available phosphorus levels for the optimum growth and feed intake were 0.6% Ca and 0.35% aP and 0.9% Ca and 0.35% aP for the optimum bone mineralization in broiler chickens.