Efficiency of microbial phytase supplementation in diets formulated with different calcium:phosphorus ratios, supplied to broilers from 22 to 33 days old

Abstract

An experiment was conducted with broilers from 22 to 33 days of age to evaluate the efficiency of six microbial phytases supplemented in diets (1500 FTU/kg) that were formulated with three different calcium:available phosphorus (Ca:P(avail)) ratios (4.5:1.0, 6.0:1.0 and 7.5:1.0). A positive control diet without phytase was formulated with a Ca:P(avail) ratio of 7.5:3.4 to meet the nutritional requirements of the broilers. The P and ash contents of the tibia, magnesium in the plasma, performance, balance and retention of phytate phosphorus (P(phyt)), intake of total P and nitrogen (N), nitrogen-corrected apparent metabolizable energy and apparent digestibility of dry matter of the diets were not influenced (p > 0.05) by the type of phytase or the dietary Ca:P(avail) ratio. However, there was an interaction (p < 0.05) between the phytase type and the Ca:P(avail) ratio for the retention coefficients of total P, Ca and N. Phytase B resulted in the highest Ca deposition in the tibia (p < 0.01). Phytases D, E and F reduced the Ca concentrations in the tibia (p < 0.01) and plasma (p < 0.05). Phytase D increased the P level in the plasma and decreased the total P excretion (p < 0.01). Phytases E and F increased Ca excretion, while phytase A reduced it (p < 0.01). Regardless of the phytase type, increasing the dietary Ca:P(avail) ratio reduced (p < 0.05) the plasma P concentration and the excretion of total P and N and, conversely, increased (p < 0.05) the plasma concentration, intake and excretion of Ca. For the rearing period evaluated, it is possible to reduce the P(avail) of the diet to 1.0 g/kg when Ca is maintained at 7.5 g/kg, and the diet is supplemented with 1500 FTU of phytase A, C, D or E/kg. This diet allows the maintenance of performance and adequate bone mineralization, and it improves the Ca, total P and P(phyt) utilization in addition to reducing the excretion of N and P into the environment.

Supplementation of fungal and/or bacterial phytase in broiler diets formulated with reduced phosphorus level and different calcium contents

“…In the diets containing the two evaluated phytases, each enzyme was supplemented at 750 FTU kg −1 concentration. The phytase inclusion level used in the present study, as well as the broiler age, were defined according to previous assays (Naves et al, 2015) The bacterial phytase (RONOZYME HiPhos ® ) corresponds to an enzyme expressed by Aspergillus oryzae genetically modified with Citrobacter braakii genes (phytase with 9,875 FTU kg −1 analysed activity). The fungal phytase (NATUPHOS ® ) was produced by Aspergillus niger genetically modified with Aspergillus ficuum gene (phytase with 9,917 FTU kg −1 analysed activity).…”

Ileal digestibility of calcium and phosphorus in broilers fed diets with different phytases and Ca:available P ratios

“…The Ca:aP ratios were defined according to P availability with the inclusion of 1,500 FTU kg -1 , as previously determined by Naves et al (2015) and reinforced by Gautier et al (2018). A total of 3.0 g kg -1 P were obtained: 2.0 g kg -1 P made totally available by 1,500 FTU kg 1 plus 1.0 g kg -1 added P. The P contents in the diets supplemented with phytase were similar to that of the control.…”

Effect of Feeding a High Calcium: Phosphorus Ratio, Phosphorous Deficient Diet on Hypophosphatemic Rickets Onset in Broilers

“…Low dietary NPP levels is a cause of bone abnormalities, leading to significantly decreased tibia ash, mineral, Ca and P content [5,24], and reduced bone density and bone strength in broilers [24]. Dietary P levels and the ratio of available P (AP) are important factors affecting bone mineralization, bone strength, gait score, and rickets in broiler chickens [14][15][16][17][18]. The rapidity of impact reflected the greater impact of a Ca:P imbalanced diet on tibia bone mineral density and ash content, and therefore, bone-breaking strength, compared with a Ca:P balanced, P-deficient diet [26].…”

“…The rapidity of impact reflected the greater impact of a Ca:P imbalanced diet on tibia bone mineral density and ash content, and therefore, bone-breaking strength, compared with a Ca:P balanced, P-deficient diet [26]. This may be because a high dietary Ca:AP ratio causes the formation of insoluble Ca-P complexes in the intestines [27], reducing the true digestibility of Ca [17], increasing Ca excretion, and decreasing plasma P concentration [16], thus leading to poor tibial mineralization [10,11]. In our study, no consistent difference was observed in lesions of visceral organs (heart, liver, spleen, kidney, bursal, gizzard, gut, thymus, and abdominal fat) between healthy chicks and lame chicks.…”

“…Vitamin D plays a role in maintaining the homeostatic balance between calcium and phosphorus in birds [12], affecting bone growth and mineral deposition [13]. In addition to absolute deficiencies of Ca or P, an improper Ca:P ratio can affect growth performance [14,15], the incidence of leg abnormalities [14], gait scores, and prevalence of hock burn and footpad lesions in birds [14][15][16][17]. When feed lacks inorganic P, rickets could occur two weeks earlier in birds fed a high Ca:P diet compared to those fed a low Ca:P diet [7].…”