Lack of a relationship between plasma fibroblast growth factor-23 and phosphate utilization in young chicks

Comparative efficacy of commercial phytases on phosphorus availability for broilers

The presence of phytate in broiler diets restricts phosphorus availability, a crucial nutrient for muscle and bone development, leading to reduced performance. To alleviate this issue, exogenous enzymes such as phytase are introduced; however, the wide variety of phytases available on the market and their effectiveness are not yet fully understood. The objective of this study was to evaluate the phosphorus equivalence of commercial phytase in broiler diets, using the standard curve, and its effects on performance, bone mineralization, intestinal histological integrity, liver relative weight, and total alkaline phosphatase in the initial phase (1 to 21 days) of broiler. We used 2,500 male broiler chickens, with an initial weight of 44 g, distributed in a completely randomized design with 10 treatments and 10 replications of 25 birds per experimental unit. The diets were formulated to meet the nutritional requirements of the birds, except for the available phosphorus (Pd) and calcium content. The treatments were divided as follows: T1-Control (CT) with 0.18% Pd; T2-CT + 0.07% aP; T3-CT + 0.14% aP; T4-CT + 0.21% aP; T5-CT + phytase 1; T6-CT + phytase 2; T7-CT + phytase 3; T8-CT + phytase 4; T9-CT + phytase 5; and T10-CT + phytase 6. For enzymatic standardization, 500 FTU/kg (Phytase Units) of each enzyme were used. Animals subjected to the highest levels of P (T2, T3, and T4) and with the addition of commercial phytases (T5, T6, T7, T8, T9, and T10) had better performance and bone mineralization results when compared to T1-CT. All phytases evaluated improved final live weight, weight gain, feed conversion, and ash and phosphorus content in the tibia and intestinal development compared to CT. Supplementing broiler diets with commercial phytases enhances performance, bone mineralization, and jejunal development from 1 to 21 days.The average phosphorus availability from phytic acid in these phytases was 0.154%. The comparison of the six commercial phytases in diets for broiler chickens, using the standard curve and supplementation with 25 g/t of commercial phytase, showed similar results, promoting improvements in performance, bone mineralization, and jejunal development.

The relationship between phosphorus retention and fibroblast growth factor 23 in broiler breeders

Previous studies with broiler breeders indicate a P retention threshold when fed daily dietary levels of non-phytate P (NPP) exceeding 320 mg. Fibroblast growth factor 23 (FGF23) is a hormone secreted by osteocytes which modulates P retention and could be the biological agent which controls the P threshold in breeders. To evaluate the relationship between FGF23 and the P retention threshold, a 4-wk study with 32-wk-old breeders was conducted with 6 dietary treatments with daily NPP intake of 216 to 576 mg/d/h with increments of 80 mg/kg diet. The goals were 1) to elucidate how plasma FGF23 corresponds with the P retention threshold in broiler breeders and 2) to determine the amount of P for optimal egg production and bone health. Results showed that between daily 288 mg and 360 mg dietary NPP intake, P retention decreased from 33 to 26% but FGF23 levels increased from 130 pg/mL to 220 pg/mL with increasing NPP. The elevation of plasma FGF23 between the range of 288 mg to 360 mg dietary NPP/d intake suggests that FGF23 is related to the P retention threshold and may be the major hormone for regulating physiological P levels when intake of daily dietary P levels are increased above 288 mg NPP.

FGF23 level in poultry chicken, a systematic review and meta-analysis

Introduction: In vertebrates fibroblast growth factor 23 (FGF23) is a phosphate regulating hormone closely linked to calcium regulation by vitamin D and parathyroid hormone (PTH). Although phosphorus, calcium and vitamin D are important for poultry well-being, relatively little is known about their levels of FGF23. Our objective was to quantitatively estimate the blood FGF23 level in birds, and to examine its relationship to diet and blood levels of other components of phosphate and calcium homeostasis. Methods: A systematic search of Agricola, Embase and Medline identified 86 studies focused on FGF23 in birds, from which 12 manuscripts reporting data for 60 independent groups of chickens were included in the analysis. Results: FGF23 levels were 256 pg/ml (Confidence interval (CI): 215, 297) in broilers (39 datasets containing 435 birds), and 256 pg/ml (CI: 178, 339) in egg-laying hens (21 datasets containing 208 birds). FGF23 levels did not correlate with dietary phosphorus, calcium or vitamin D, or with plasma calcium or PTH. FGF23 levels demonstrated a trend to positively correlate with plasma phosphate and a strongly and positive correlation with plasma vitamin D. Discussion: This study provides normative estimates of FGF23 levels in poultry birds and new insights into the regulation of calcium and phosphate homeostasis.

Regulation of bone phosphorus retention and bone development possibly by related hormones and local bone-derived regulators in broiler chicks

BACKGROUND

Phosphorus is essential for bone mineralization in broilers, however, the underlying mechanisms remain unclear. We aimed to investigate whether bone phosphorus retention and bone development might be regulated by related hormones and local bone-derived regulators in broilers.

METHODS

Broilers were fed diets containing different levels of non-phytate phosphorus (NPP) 0.15%, 0.25%, 0.35%, 0.45% and 0.55% or 0.15%, 0.22%, 0.29%, 0.36% and 0.43% from 1 to 21 or 22 to 42 days of age. Serum and tibia samples were collected for determinations of bone phosphorus retention and bone development parameters, related hormones and local bone-derived regulators of broiler chickens on d 14, 28 and 42, respectively.

RESULTS

Tibia ash phosphorus, total phosphorus accumulation in tibia ash (TP_TA), bone mineral concentration (BMC), bone mineral density (BMD), bone breaking strength (BBS), and ash on d 14, 28 or 42, serum 1,25-dihydroxyvitamin D₃ (1,25(OH)₂D₃) on d 28 and 42, mRNA expressions of tibia fibroblast growth factor 23 (FGF23) and dentin matrix protein 1 (DMP1) on d 14 and 28 increased linearly or quadratically (P < 0.05), while serum parathyroid hormone (PTH) on d 28, tibia alkaline phosphatase (ALP) on d 14, 28 and 42, bone gal protein (BGP) on d 14, and mRNA expression of tibia phosphate-regulating gene with homologies to endopeptidases on the X chromosome (PHEX) on d 14 and 28 decreased linearly or quadratically (P < 0.04) as dietary NPP level increased. TP_TA, BMC, BMD, and ash on d 28 and 42, BBS on d 28, and ash phosphorus on d 42 were positively correlated (r = 0.389 to 0.486, P < 0.03) with serum 1,25(OH)₂D₃. All of the above parameters were positively correlated (r = 0.380 to 0.689, P < 0.05) with tibia DMP1 mRNA expression on d 14, 28 and 42, but negatively correlated (r = - 0.609 to - 0.538, P < 0.02) with serum PTH on d 28, tibia ALP on d 14, 28 and 42, and BGP on d 14. TP_TA, BMC and ash on d 14 and BMD on d 28 were negatively correlated (r = - 0.397 to - 0.362, P < 0.03) with tibia PHEX mRNA expression, and BMD on d 28 was positively correlated (r = 0.384, P = 0.04) with tibia FGF23 mRNA expression.

CONCLUSIONS

These results suggested that bone phosphorus retention and bone development parameters had moderate to strong correlations with serum PTH and 1,25(OH)₂D₃ and tibia DMP1, PHEX, FGF23, ALP and BGP in broilers during the whole growth period, and thus they might be partly regulated by these related hormones and local bone-derived regulators.