Dietary Phosphorus Levels Research Articles

Effect of dietary high non-phytate phosphorus level on growth performance and metabolism of calcium and phosphorus in Lion-head geese

The aim of this study was to investigate the effect of dietary high non-phytate phosphorus (NPP) level on the growth performance and metabolism of Ca and P in Lion-head geese during starter and grower-finisher periods. A total of 384 goslings at d 1 and 240 geese at d 29 were divided into 3 treatments with 4 replicate pens each treatment for Exp. 1 (the starter period for d 1–21) and Exp. 2 (the grower-finisher period for d 29–72), respectively. The 3 supplemental NPP levels (Ca: NPP ratio) in diets were 0.40% (2.38), 0.60% (1.58) and 0.80% (1.19) for Exp. 1 and were 0.30% (2.83), 0.50% (1.70) and 0.70% (1.21) for Exp. 2. In Exp. 1, final body weight, average daily gain and average daily feed intake of goslings fed a diet containing 0.80% NPP (Ca: NPP ratio,1.19) were decreased (P < 0.05) compared to birds fed a diet containing 0.60% NPP (Ca: NPP ratio, 1.58) at the starter period, with no difference (P > 0.05) between the two diets containing NPP of 0.40% (Ca: NPP ratio, 2.38) and 0.80% (Ca: NPP ratio,1.19). At d 21 of goslings, the concentrations of Ca, P, parathyroid hormone and bone gla-protein, and alkaline phosphatase activity in serum were decreased (P < 0.05) linearly in response to the increasing NPP level and decreasing Ca: NPP ratio in diets. At d 72 of geese, tibia bone Ca content was decreased (P < 0.05) linearly as dietary NPP level increased and Ca: NPP ratio decreased. Our results indicated that dietary high NPP level along with low Ca: NPP ratio can reduce growth performance and disrupt Ca and P metabolism together with the changes of serum characteristics in goslings at the starter period.

Effect of suboptimal levels of non-phytate phosphorus and exogenous phytase on precaecal digestibility of phosphorus and calcium in laying hens

The precaecal digestibility of phosphorus and calcium in laying hens was evaluated at two dietary levels of non-phytate phosphorus (NPP; 1.58 and 2.03 g/kg) and two levels of exogenous 3-phytase (F; 0 and 300 phytase units (FTU)/kg). A total of 192 ISA Brown hens were used for the study, and were housed in enriched cages (8 per cage). At the end of the experiment, which was the peak of the egg production, the content of the posterior half of the ileum from each hen was collected. The lower level of NPP significantly (P &amp;lt; 0.05) improved the precaecal phosphorus digestibility coefficient. There was no significant difference in the amount of absorbed phosphorus between the lower and the higher level of NPP. The level of NPP with supplementation of exo-genous phytase had a significant effect (P &amp;lt; 0.001) on the concentration of phosphorus in ileum, while the higher level of NPP increased phosphorus concentration in the ileum and phytase decreased phosphorus content in the ileal digesta. The phytase had no significant effect on phosphorus precaecal digestibility. There was no significant effect of the both factors, level of NPP, and exogenous phytase on the daily calcium intake, the amount of absorbed calcium, the content of calcium in ileal digesta, and on the precaecal digestibility of calcium. However a significant effect (P &amp;lt; 0.05) of the interaction between NPP and phytase was observed on the amount of absorbed calcium and on the precaecal digestibility coefficient. It can be concluded that the estimation of phosphorus ileal digestibility depends on the level of dietary phosphorus.

Effect of low levels of dietary available phosphorus on phosphorus utilization, bone mineralization, phosphorus transporter mRNA expression and performance in growing pigs

ABSTRACTA study was conducted to examine the effects of different dietary levels of available phosphorus (aP) on P excretion, bone mineralization, performance and the mRNA expression of sodium-dependent P transporters in growing pigs. Sixty-day old growing pigs (n = 54) with an average initial BW of 19.50 ± 1.11 kg were randomly allocated to a control diet (C) containing 0.23% available phosphorus (aP), T1 containing 0.17% aP and T2 containing 0.11% aP. There were 6 pens per treatment with 3 pigs per pen. Body weight and feed intake were measured weekly. At the end of each week, one pig from each pen was housed in a metabolic crate for 24 h to collect fecal and urine samples and then sacrificed to obtain third metacarpal (MC3) bones and jejunal and kidney samples. Bones were scanned by Dual Energy X-ray Absorptiometry (DEXA). Fecal and urine samples were sub-sampled and analyzed for P content. The expression of P transporter mRNA in jejunum and kidney samples was measured using quantitative real-time polymerase chain reaction (qRT-PCR). Data were analyzed using GLM procedure of the Statistical Analysis System (SAS Institute version 9.2). Pigs fed the T2 diet had reduced (P < 0.05) average daily gain (ADG) and gain to feed (G:F) compared to those fed the C diet during week 2. Overall, ADG and G:F were also reduced (P < 0.05) in pigs fed the T2 diet compared to those fed the C and T1 diets. Bone mineral density (BMD) and bone mineral content (BMC) were reduced (P < 0.05) in pigs fed the T2 diet compared to those fed the C diet throughout the experiment. At week 1, jejunal mRNA expression of Na (+)-dependent phosphate transporter 2 (SLC34A2) was increased (P < 0.01) in pigs fed the T2 diet compared to C diet. Renal mRNA expression of Na(+)-dependent phosphate transporter 1 (SLC34A1) and SLC34A3 were increased (P < 0.05) in pigs fed the T2 diet compared to those fed the C diet at week 2 and was accompanied by lower (P < 0.05) urinary P in pigs fed the T2 diet during week 2 and week 3. In conclusion, growing pigs are highly sensitive to low dietary P as shown by reduced ADG, bone mineralization and urinary P level, but moderate reduction in dietary P up to 0.17% aP in the diet has the potential to reduce environmental pollution by reducing P concentration in swine manure and without compromising performance.

Effects of Dietary Phosphorus Levels on Growth Performance, Plasma Biochemical Parameters and Relative Gene Expression of Lipogenesis of Bighead Carp, Aristichthys nobilis

An 8-week feeding trial was conducted to investigate the effects of dietary phosphorus levels on growth performance, plasma biochemical parameters, and lipogenesis gene expression of bighead carp. The results showed that weight gain (WG) and specific growth rate (SGR) increased with increasing dietary phosphorus levels up to 1.12%, and after that decreased. Feed conversion ratio (FCR) showed a converse trend compared with WG. Whole body protein and lipid contents significantly increased and decreased with increasing dietary phosphorus levels, respectively (P&lt;0.05), whereas moisture and ash contents were not significantly affected by the dietary phosphorus levels (P&gt;0.05). The highest values of the hepatosomatic index (HSI), total protein, and albumin contents were observed with 1.12% dietary phosphorus supplementation (P&lt;0.05). Glucose levels increased with dietary phosphorus up to the level 1.32% phosphorus supplementation, and then decreased. Serum total cholesterol, total triglyceride, aspartate aminotransferase, alanine aminotransferase, and alkaline phosphates activity were not significantly affected by dietary phosphorus levels (P&gt;0.05). Excess phosphorus levels (1.32% and 1.59%) significantly down-regulated the relative gene expression levels of sterol regulatory element binding protein (SREBP) -1 and fatty acid synthase (FAS) (P&lt;0.05). Based on WG and FCR, the optimal dietary phosphorus level should be 1.16%, using quadratic regression analysis.

Effects of Dietary Phosphorus Levels on Growth Performance, Plasma Biochemical Parameters and Relative Gene Expression of Lipogenesis of Bighead Carp, Aristichthys nobilis

An 8-week feeding trial was conducted to investigate the effects of dietary phosphorus levels on growth performance, plasma biochemical parameters, and lipogenesis gene expression of bighead carp. The results showed that weight gain (WG) and specific growth rate (SGR) increased with increasing dietary phosphorus levels up to 1.12%, and after that decreased. Feed conversion ratio (FCR) showed a converse trend compared with WG. Whole body protein and lipid contents significantly increased and decreased with increasing dietary phosphorus levels, respectively (P&lt;0.05), whereas moisture and ash contents were not significantly affected by the dietary phosphorus levels (P&gt;0.05). The highest values of the hepatosomatic index (HSI), total protein, and albumin contents were observed with 1.12% dietary phosphorus supplementation (P&lt;0.05). Glucose levels increased with dietary phosphorus up to the level 1.32% phosphorus supplementation, and then decreased. Serum total cholesterol, total triglyceride, aspartate aminotransferase, alanine aminotransferase, and alkaline phosphates activity were not significantly affected by dietary phosphorus levels (P&gt;0.05). Excess phosphorus levels (1.32% and 1.59%) significantly down-regulated the relative gene expression levels of sterol regulatory element binding protein (SREBP) -1 and fatty acid synthase (FAS) (P&lt;0.05). Based on WG and FCR, the optimal dietary phosphorus level should be 1.16%, using quadratic regression analysis.

Dietary non-phytate phosphorus requirement of broilers fed a conventional corn-soybean meal diet from 1 to 21 d of age

An experiment was conducted to investigate the effect of dietary non-phytate phosphorus (NPP) level on growth performance, bone characteristics and phosphorus metabolism-related gene expressions, so as to evaluate the dietary NPP requirement of broiler chicks fed a conventional corn-soybean meal diet from 1 to 21 d of age. A total of 540 day-old Arbor Acres male chicks were randomly allocated to one of nine treatments with six replicate cages of 10 birds per cage in a completely randomized design, and fed a basal corn-soybean meal diet (containing 0.08% of NPP) supplemented with 0.10, 0.15, 0.25, 0.30, 0.35, 0.40, 0.45, or 0.50% of inorganic phosphorus in the form of CaHPO4·2H2 O, respectively. Each diet contained the constant calcium content of about 1.0%. The results showed that daily weight gain, serum inorganic P, tibia bone strength, tibia ash percentage, tibia bone mineral content (BMC) and density (BMD), middle toe ash percentage, middle toe BMC and BMD were affected (P < 0.0001) by dietary NPP level, and increased linearly (P < 0.0001) and quadraticly (P < 0.004) as dietary NPP levels increased. The gene expression of type IIb sodium-phosphate cotransporter (NaPi-IIb) in the duodenum was affected (P < 0.03) and decreased linearly (P < 0.002) as dietary NPP levels increased. Dietary NPP requirements estimated based on fitted broken-line models (P < 0.0001) of the sensitive indices including daily weight gain, tibia bone strength, tibia ash percentage, tibia BMC and BMD as well as middle toe ash percentage were 0.34∼0.39%. The results from this study indicate that tibia BMC and BMD might be new, sensitive, and noninvasive criteria to evaluate the dietary NPP requirements of broilers, and the dietary NPP requirement is 0.39% for broiler chicks fed a conventional corn-soybean meal diet from 1 to 21 d of age.

Effects of dietary calcium levels on growth performance and bone characteristics in pigs in grower-finisher-transitional phase

The objective of this experiment was to determine the effects of dietary calcium (Ca) levels on growth performance and bone development of growing and finishing pigs. A total of 150 crossbred pigs (37.0±4.0kg BW) were randomly assigned to 5 treatment groups: (1) low Ca levels in both grower and finisher phases (LL), (2) low Ca level in grower phase and high Ca level in finisher phase (LH), (3) medium Ca levels in both grower and finisher phases (MM), (4) high Ca level in grower phase and low Ca level in finisher phase (HL), and (5) high Ca levels in both grower and finisher phases (HH). The dietary phosphorus (P) levels were fixed. The animal trial was conducted for 60days. When the average pen BW reached approximately 60kg, the pigs were switched to finisher diets. Pig performance was not affected by dietary treatments during either the grower or finisher phases. During the grower phase, the bone mineral density (BMD) and bending moment of the fourth metacarpal and metatarsal bones were lower (P<0.05) in pigs fed the low Ca diets than in those fed the medium Ca diets. During the finisher phase, P weight, BMD and bending moment of the fourth metacarpal and metatarsal bones were not different for pigs fed the LH and HL diets compared with pigs fed the HH diet. The bending moment of the fourth metacarpal bone and fat-free dry weight of the fourth metatarsal bone were lower (P<0.05) in pigs fed the LH diet compared with those fed the MM diet. In conclusion, a compensatory effect occurred in bone characteristics at the end of the finisher phase when the high Ca diet was introduced in the finisher phase, following a low-Ca diet during the grower phase. However, pigs fed LH diet did not surpass the level of bone mineralization achieved by pigs fed the MM diet.

Enclosure experiment of effects of dietary phosphorus level on water quality, phosphorus budget, and plankton composition in intensive culture of crucian carp

Enclosure experiment was carried out to evaluate the effects of dietary phosphorus levels on water quality, phosphorus budget, and plankton composition in intensive culture of crucian carp (Carassius auratus). Monocalcium phosphate was used to formulate extruded feed containing total phosphorus of 8.7 (D1), 11.4 (D2), 13.5 (D3), and 18.4 (D4) g kg−1. Twelve polyethylene enclosures (each 4 × 4 × 1.5 m depth) were assigned to four groups with each one stocked with 120 juveniles (44.08 ± 1.36 g). Fish was fed twice daily at a rate of 3% body weight in the experiment. After 70 days of feeding, growth and survive rate of crucian carp were not affected by diet of different P level. It was found that physiochemical factors in all the enclosures did not show obvious threat on fish. Diets of different P level did not affect dissolved oxygen (DO), secchi depth (SD), total ammonium nitrogen (TAN), and total nitrogen (TN) concentration in enclosures. However, increased diet P level seemed to increase averaged pH, soluble reactive phosphorus (SRP), and total phosphorus (TP) concentration and decrease nitrite concentration and TN/TP. During later period of experiment, treatments with high diet P level (D3 and D4 treatments) had very high cyanobacterial biomass dominated by Microcystis spp., while phytoplankton in D1 and D2 treatments was mainly composed of edible algae. Composition and density of zooplankton in different treatments varied in similar pattern. Peak density of cladocerans (mainly Moina spp.) seemed to be related to diet P level. The present study indicated that changing P level in diets might bring complicated changes to the intensive crucian carp culture ecosystem.

Phosphorus and nitrogen utilization responses of broiler chickens to dietary crude protein and phosphorus levels

A study was conducted to investigate the effect of dietary CP levels on pre-cecal digestibility and total tract retention of phosphorus (P) in broiler chickens. A total of 384 14-day-old male broiler chickens were used in a randomized complete block design with 8 treatments and 6 replicates per treatment in a 7-d experimental period. There were 8 corn-soybean meal-based diets in a 2 × 4 factorial arrangement, which included 2 CP levels (10.7 or 21.5%) and 4 apparent total tract digestible P (ATTDP) levels (0.18, 0.32, 0.45, or 0.59%). Soybean meal and mono-calcium phosphate were used to adjust the CP and ATTDP levels, respectively. At the end of the experiment, BW was recorded and digesta samples from the distal two-thirds of ileum and mucosa samples from the middle of the jejunum were collected. Total RNA also was isolated from mucosa samples and used for real-time PCR to determine the gene expression of sodium-phosphate co-transporter IIb (NaPi-IIb). Results showed that low dietary CP level limited the growth performance (P<0.01), pre-cecal digestion, and total tract retention of P (P<0.01), and NaPi-IIb gene expression (P<0.05), compared with high dietary CP. Pre-cecal digestion and total tract retention of P (g/kg DM intake) linearly increased (P<0.01) with increasing ATTDP levels in both low and high CP groups. In conclusion, this study suggests an interrelationship between N and P digestion such that CP deficiency decreased the growth performance of birds consequently reducing pre-cecal P digestion in broiler chickens. Total tract retention of CP and P are linked with each other and body tissue growth may be a driver of the deposition of these 2 nutrients. Supplementation of protein may be necessary in diets during P digestibility studies to ameliorate an effect of protein deficiency on P digestion and retention.

0982 Influence of dietary crude protein and phosphorus levels on the utilization of crude protein and phosphorus in growing pigs

0982 Influence of dietary crude protein and phosphorus levels on the utilization of crude protein and phosphorus in growing pigs

Effects of dietary oil sources, calcium and phosphorus levels on growth performance, carcass characteristics and bone quality of broiler chickens

ABSTRACTThe study investigated the effects of varying dietary calcium (Ca) level and oil sources on the growth performance and carcass quality of broiler chickens. A total of 378, 1-day-old birds (Cobb 500) were fed either 6% palm oil, soybean oil (SO) or linseed oil (LO) in combination with three dietary levels of calcium (1.00%, 1.25% and 1.50%) for 6 weeks. Birds fed SO had higher body weight (BW) compared with those fed LO (p < .05). However, feed efficiency, carcass and bone quality were similar among the oil treatments. Regardless of the oil source, chicken fed diets containing 1.50% of Ca had lower BW compared with those fed 1.00% and 1.25% of Ca. In contrast, birds fed 1.25% of Ca had significantly higher (p < .05) bone quality than those fed 1% of Ca. It can be concluded that increasing the level of calcium up to 1.25% improved bone quality regardless of the type of oil.

Effect of dietary phosphorus levels on growth and body composition of crucian carp, Carassius auratusunder indoor and outdoor experiments

Indoor and outdoor experiments were carried out simultaneously to evaluate the effects of dietary phosphorus levels on growth performance and body composition of crucian carp. Monocalcium was used to formulate extruded feed containing available phosphorus (AP) of 1.5 (D1), 4.7 (D2), 6.3 (D3) and 9.0 (D4) g kg−1. Twelve 500-L recirculating tanks were assigned to four triplicate groups with each tank stocked with 15 juveniles (39.88 ± 0.14 g) for indoor experiment. Twelve polyethylene enclosures were assigned to four groups with each one stocked with 120 juveniles (44.08 ± 1.36 g). After 8 weeks of feeding, survival ranged from 96% to 100%. Weight gain, special growth rate, protein efficiency ratio and feed conversion rate did not show significant differences among dietary treatments in both experiments. Fish cultured in the enclosures grew better, although D1 and D2 treatments did not reach significant level. Crude protein and phosphorus content of the fish were not significantly affected by dietary phosphorus level. Moisture, crude lipid, crude ash and vertebrae phosphorus were significantly affected by different phosphorus levels. Based on vertebrae phosphorus, crucian carp cultured in the tanks and in the enclosures showed phosphorus deficiency under 4.7 g kg−1 and 6.3 g kg−1 AP, respectively.

Dietary total phosphorus supplementation in goldfish diets

Although goldfish ( Carassius auratus ) is an important species for the ornamental fish industry, few data are available regarding the nutrient requirement of this species, with emphasis to mineral nutrition. Thus, we designed a 45-day feeding trial to evaluate the effect of dietary total phosphorus (P) levels on growth performance and carcass mineral composition of goldfish fingerlings. 210 goldfish with 1.18 ± 0.04 g were randomly stocked into 30 3L-aquaria in a completely randomized design. Test diets were formulated to contain the following dietary total P levels: 3.5, 6.5, 9.5, 12.5 and 15.5 g kg -1 . Dietary P affected all growth parameters and carcass macrominerals deposition, however, the micromineral carcass composition was not affected. No P deficiency signs were observed throughout the experiment. The linear broken-line model best fitted to daily weight gain, feed conversion ratio, specific growth rate, protein efficiency ratio, P retention, and whole-body P concentration at 8.2, 11.4, 8.2, 11.4, 15.5 and 7.1 g kg -1 dietary P, respectively. An exponential model best fitted to phosphorus utilization data with an estimated requirement of 8.6 g kg -1 . In sum, the use of total P levels between 7.13 and 11.4 g kg-1 in goldfish diets seems to meet the requirement for maximum growth, feed utilization and proper whole-body mineralization.

Effect of dietary phosphorus level on the determination of standardized and true total tract digestibility of phosphorus for growing pigs

The current study was conducted to investigate the effect of dietary phosphorus (P) concentration on the estimation of standardized total tract digestibility (STTD) and true total tract digestibility (TTTD) of P for growing pigs fed corn- and soybean meal (SBM)-based diets. Fifty-six barrows with an average initial BW of 30.9kg were used in a randomized complete block design with 7 diets. The 7 diets included a P-free diet and 6 corn- and SBM-based diets that contained the assay ingredient of 150, 300, 450, 600, 750, and 900g/kg. The assay ingredient consisted of corn and SBM at a fixed ratio of 3:2 by weight. The P-free diet was used to estimate endogenous P loss (EPL) of pigs and to calculate STTD of P in the assay ingredient. The total collection procedure was used to calculate P digestibility with a 5-days adjustment period followed by a 7-days collection period using chromic oxide as a marker to indicate the initiation and termination of fecal collection. The results showed that daily P intake, fecal P output, digested P, and retained P increased linearly with increasing dietary P level for pigs fed corn- and SBM-based diets (P<0.01). Apparent total tract digestibility (ATTD) of P, urinary P output, and P retention were not affected by dietary P content (P>0.05). There was a linear decrease in STTD of P (from 54.13 to 43.42%) with graded inclusion of dietary P (P<0.01). Regressing daily digested P against daily P intake, the TTTD of P were estimated at 40.24 and 38.22% for pigs fed low P diets (the assay ingredient level at 150, 300, and 450g/kg) and high P diets (the assay ingredient level at 600, 750, and 900g/kg), respectively. The estimates of TTTD of P were not statistically different between pigs fed low P diets and high P diets (P>0.05). In conclusion, increasing dietary P from graded inclusion of the assay ingredient reduced the estimated values of STTD of P but did not affect the estimates of TTTD of P determined by the regression method.

Effect of dietary phosphorus levels on meat quality and lipid metabolism in broiler chickens

To analyze the influence of dietary phosphorus (P) levels on meat quality and lipid metabolism, a 42-day feeding experiment (P deficient group; normal group; high P level groups of H1 and H2, respectively) using 100 one-day-old broilers was conducted. Results demonstrated that the quality of broiler chicken meat in deficient or high P groups decreased relative to the normal group. High P diets resulted in increased lightness, redness values, shear forces and decreased fatty acid contents and intramuscular fat content in breast meat (p<0.01). Compared with normal group, lower malic enzyme activity, higher fatty acid synthase and AMP-activated protein kinase activities were observed in the treatment groups (p<0.05). Chickens fed with normal diets had the lowest serum total cholesterol and triglyceride levels which differed from that of other treatments (p<0.05). High-P diets significantly decreased the lipid accumulation in the liver (p<0.01), whereas phosphorus levels in breast meat increased significantly (p<0.01). It can be concluded that deficient or higher P levels could affect meat quality and expression of indicators on lipid metabolism of broiler chickens.

An optimal dietary non-phytate phosphorus level of broilers fed a conventional corn–soybean meal diet from 4 to 6 weeks of age

It is imperative to evaluate precise nutrient requirements of animals in order to optimize productivity and minimize feed cost and nutrient excretions. The current non-phytate phosphorus (NPP) recommendation for broilers is based on the papers published 30 years ago. However, today’s commercial birds are quite different from those before 30 years. Therefore, the present experiment was conducted with growing male broiler chickens to evaluate an optimal dietary NPP level of broiler chickens fed a conventional corn–soybean meal diet from 4 to 6 weeks of age. The 1-day-old chicks were fed corn–soybean meal diet containing 0.39% NPP from 1 to 3 weeks of age. At 22 days of age, 360 birds were selected and randomly allotted by BW to one of 10 dietary treatments with six replicate cages of six birds per cage for each treatment. Birds were fed the P-unsupplemented corn–soybean meal basal diet and the basal diet supplemented with inorganic P as CaHPO4·H2O ranging from 0.00% to 0.45% with 0.05% increment from 4 to 6 weeks of age. The dietary NPP levels were 0.09%, 0.14%, 0.20%, 0.24%, 0.30%, 0.34%, 0.38%, 0.45%, 0.49% and 0.54%, respectively, and the dietary Ca level was fixed at 0.90% for all treatments. The results showed that average daily gain, serum inorganic P concentration, tibia bone strength, tibia ash percentage and P percentage, tibia bone mineral content (BMC) and density (BMD), middle toe ash percentage and P percentage, middle toe BMC, total body BMC and BMD were affected (P<0.0001) by dietary NPP level, and increased linearly (P<0.0001) and quadratically (P<0.003) as dietary NPP levels increased. Optimal dietary NPP levels estimated based on fitted broken-line models (P<0.0001) of the above indices are 0.21%, 0.29%, 0.29%, 0.29%, 0.29%, 0.31%, 0.29%, 0.30%, 0.27%, 0.29% and 0.28%, respectively. It is suggested that the total body BMC and BMD, and middle toe ash P and BMC might be new, sensitive and non-invasive criteria to evaluate the dietary NPP requirements of broilers. The optimal dietary NPP level would be 0.31% for broiler chickens fed a conventional corn–soybean meal diet from 4 to 6 weeks of age.

Optimization of phosphorus content in high plant protein practical diets for Senegalese sole (Solea senegalensis,Kaup 1858) juveniles: influence on growth performance and composition of whole body and vertebrae

Practical diets containing PP sources were elaborated. Increasing levels of di-calcium phosphate were added to diets leading to five different dietary available P levels: 2.5, 3.2, 6.0, 6.5 and 8.0 g kg−1 dry diet. The dietary treatments were tested in 13.5 g Senegalese sole juveniles throughout an 82-day experimental period. Dietary P content had no effect on the productive parameters, while nutrient intake was also similar among dietary treatments, except P intake. Dry matter ADC ranged between 54.9% and 64.0%, and the highest P ADCs value (47.2 ± 0.7%) was achieved in fish fed AP6.0. Dietary phosphorus level significantly influenced body lipid and P compositions. Regression analysis performed on whole-body P and ash contents fitted to quadratic models. Vertebral bone P content was low but increased significantly with increasing dietary P levels. Bone density and deformities occurrence were, however, similar between experimental conditions. An altered status of bone formation–resorption processes in soles fed the lowest P content diet might be inferred from ALP and TRAP activities. In conclusion, overall results state a high tolerance of Senegalese sole to low P content diets and support the utilization of practical diets with high plant protein content.

Treatment of grain with organic acids at 2 different dietary phosphorus levels modulates ruminal microbial community structure and fermentation patterns in vitro

Recent data indicate positive effects of treating grain with citric (CAc) or lactic acid (LAc) on the hydrolysis of phytate phosphorus (P) and fermentation products of the grain. This study used a semicontinuous rumen simulation technique to evaluate the effects of processing of barley with 50.25g/L (wt/vol) CAc or 76.25g/L LAc on microbial composition, metabolic fermentation profile, and nutrient degradation at low or high dietary P supply. The low P diet [3.1g of P per kg of dry matter (DM) of dietary P sources only] was not supplemented with inorganic P, whereas the high P diet was supplemented with 0.5g of inorganic P per kg of DM through mineral premix and 870mg of inorganic P/d per incubation fermenter via artificial saliva. Target microbes were determined using quantitative PCR. Data showed depression of total bacteria but not of total protozoa or short-chain fatty acid (SCFA) concentration with the low P diet. In addition, the low P diet lowered the relative abundance of Ruminococcus albus and decreased neutral detergent fiber (NDF) degradation and acetate proportion, but increased the abundance of several predominantly noncellulolytic bacterial species and anaerobic fungi. Treatment of grain with LAc increased the abundance of total bacteria in the low P diet only, and this effect was associated with a greater concentration of SCFA in the ruminal fluid. Interestingly, in the low P diet, CAc treatment of barley increased the most prevalent bacterial group, the genus Prevotella, in ruminal fluid and increased NDF degradation to the same extent as did inorganic P supplementation in the high P diet. Treatment with either CAc or LAc lowered the abundance of Megasphaera elsdenii but only in the low P diet. On the other hand, CAc treatment increased the proportion of acetate in the low P diet, whereas LAc treatment decreased this variable at both dietary P levels. The propionate proportion was significantly increased by LAc at both P levels, whereas butyrate increased only with the low P diet. Treatments with CAc or LAc reduced the degradation of CP and ammonia concentration compared with the control diet at both P levels. In conclusion, the beneficial effects of CAc and LAc treatment on specific ruminal microbes, fermentation profile, and fiber degradation in the low P diet suggest the potential for the treatment to compensate for the lack of inorganic P supplementation in vitro. Further research is warranted to determine the extent to which the treatment can alleviate the shortage of inorganic P supplementation under in vivo conditions.

Effects of Excess Dietary Phosphorus on Fecal Phosphorus Excretion and Water Extractable Phosphorus in Horses

Phosphorus excretion was studied in horses fed excess phosphorus. The hypothesis of this study was that the concentration of phosphorus and water extractable phosphorus (WEP) in the feces of sedentary horses would reflect the level of dietary phosphorus. Eight Standardbred mares were divided into two groups and received diets of grass hay and grain. The high phosphorus (HP) group received 142 g/d of monosodium phosphate (NaH2PO4), formulated to provide 4.5-times dietary phosphorus requirement, or 65-g phosphorus per day. The low phosphorus (LP) group received 28 g of phosphorus per day in the basal diet. These amounts were based on horses consuming 2% of body weight per day as hay plus supplemental grain. After a 7-day diet adaptation, a 5-day collection was conducted. Animals were housed from 4 PM until 8 AM the following morning without bedding during the collection period. After the first period, horses underwent a 10-day washout and then groups were crossed over for a second 7-day adaptation and 5-day collection. Feces was collected daily, weighed, and a 10% of aliquot taken. At the end of each collection period, feces was composited for each horse and analyzed for nitrogen, potassium, phosphorus, and WEP. Fecal phosphorus and WEP content were greater in the HP group (8.1 ± 0.3 vs. 6.8 ± 0.3 g/kg, respectively) than the LP group (3.6 ± 0.3 vs. 2.1 ± 0.3 g/kg, respectively; P < .05). Overfeeding a phosphorus supplement increased phosphorus and WEP in the manure; WEP may be useful for determining phosphorus runoff risk.

Dietary Phosphorus Requirements of Juvenile Hybrid Tilapia (Oreochromis niloticus♀× O. Aureus♂) Fed Fishmeal-free Practical Diets

A growth trial was conducted to estimate the optimum levels of dietary phosphorus (P) for juvenile hybrid tilapia (Oreochromis niloticus × O. aureus) fed fishmeal-free practical diets. Hybrid tilapia (1.68 ± 0.08 g) were fed diets containing various levels (0.0%, 0.2%, 0.4%, 0.6%, 0.8% and 1.0%) of additional inorganic phosphorus for 10 weeks using two different sources of phosphorus：calcium dihydrogen phosphate (MCP), and sodium dihydrogen phosphate (MSP). Hybrid tilapia fed the P-supplemented diets showed significantly higher weight gain (WG) and mineral deposition than those fed the unsupplemented diet. Based on weight gain and vertebral phosphorus content, the available phosphorus requirements of hybrid tilapia were estimated as 1% and 1.31% (0.6% and 0.9% based on additional phosphorus content) respectively, when MSP was used as a phosphorus source. When MCP was the phosphorus source, the requirement estimated for weight gain was 0.95% (0.61% based on additional phosphorus content). In addition, MCP contributed to increased growth and a higher mineral deposition rate than did MSP, in freshwater-reared hybrid tilapia.