Determining the Bioavailability Percentage of Bone Ash Phosphorus Compared to Monocalcium Phosphate and Its Effect on Performance, Bone Quality and Phosphorus Digestibility in Broilers

Introduction: Phosphorus (P) and calcium (Ca) are macro-minerals for normal growth and development. Phosphorus plays a vital role in muscle function, enzyme activity, lipid metabolism, bone mineralization, maintaining osmotic and acid-base balance, energy metabolism, amino acid metabolism, and protein synthesis. In addition, in layers, P is required to replace tissue metabolites such as nucleotides and phospholipids, maintain skeletal integrity, and produce the egg. Also, Ca is essential for eggshell formation, coagulation, muscle, and nerve function. Bone is a rich source of P and Ca, which can be converted into bone ash (BA) as an organic source to supply P and Ca. Today, BA has been introduced as a suitable alternative for mineral sources of P and Ca in the poultry industry. Barshan et al reported in 2019 that the use of BA compared to dicalcium phosphate caused a significant increase in weight in broilers. The purpose of this study was to use bone ash as a dietary P source and to investigate the P bioavailability in it compared to monocalcium phosphate (MCP) as a standard source.Materials and Methods: 350 one-day-old broilers were used in a completely randomized design with 7 treatments and 5 repetitions. The dietary treatments were: 1) basic diet containing 0.11% of available P; 2, 4, 3) supplementing the basic diet with 0.05, 0.1, and 0.15% P from MCP source; 5, 6, 7) supplementing the basic diet with 0.05, 0.1, and 0.15% P from BA source. All experimental diets contained 0.78% Ca. At the end of the experiment, the P bioavailability in the BA was obtained based on the P consumed in relation to the daily weight gain and tibia bone ash by the slope-ratio method. Also, the investigated parameters such as digestibility and antibody titer against sheep red blood cells (SRBC) were analyzed in a factorial design.Results and Discussion: The results showed that based on the weight gain in the grower (10 to 25 days) and finisher (26 to 35 days) periods, the bioavailability of P in BA was 82.37% and 93.24%, respectively. Therefore, it can be concluded that with the increase in the consumption time of BA, its P bioavailability has also increased and it has been able to compensate for the lack of growth well and almost similar to monocalcium phosphate. Also, based on the percentage of ash and P of tibia bone, the P bioavailability was 92.86% and 96.39%, respectively.The factorial analysis of digestibility results also showed that by increasing the level of P in diet and using MCP, the percentage of dry matter digestibility increases significantly (P<0.05). Also, the percentage of P digestibility increased numerically with the increase in diet P and the use of BA. Also, factorial analysis of the data related to the production of antibody titer against sheep red blood cells, we observed that the only significant difference in the main effects was for the total antibody titer and IgG in the secondary response; So that the antibody titer produced in the secondary response was significantly higher in chickens fed with monocalcium phosphate than in chickens fed with bone ash (P<0.05). The results of the bone quality test showed that the shear and tensile stress for the tibia was significantly higher in chickens fed with 0.26% P (P<0.05); but there was no significant difference between chickens fed with MCP and BA. An increase in tensile and shear stress means that more force is required to break these bones, which indicates the greater strength of these bones. Measuring the percentage of ash and phosphorus (P) in tibia bones showed that as the dietary phosphorus level increased, the percentage of ash and phosphorus in the tibia also increased significantly (P<0.05). Additionally, using monocalcium phosphate (MCP) in the diet resulted in a significant increase in tibia phosphorus (P<0.05); however, there was no significant difference in the percentage of tibia bone ash. Given the limited availability and high cost of phosphorus and calcium mineral resources, it is essential to find suitable alternatives. Bone ash (BA) is a rich source of phosphorus and calcium, which can be used as an organic source to supply these minerals in industrial poultry diets. Consistent with our results, Van Haren et al. reported that BA can compensate for growth deficits in broiler chickens, similar to diets supplemented with dicalcium phosphate (DCP) and MCP, compared to diets without a phosphorus source.Conclusion: In general, according to the results, it can be concluded that the bioavailability of P in BA is 92 to 96% compared to MCP. This result shows the good ability of BA to replace mineral sources of P. Also, since the absorbability of MCP is higher than dicalcium phosphate (DCP), it can be concluded that BA can have the same efficiency as DCP and be introduced as a substitute in the poultry industry.