Dietary Phosphorus Levels Research Articles

Responses of laying performance, eggshell quality, calcium, and phosphorus metabolism to feeding patterns and dietary available phosphorus levels in aged laying hens

Responses of laying performance, eggshell quality, calcium, and phosphorus metabolism to feeding patterns and dietary available phosphorus levels in aged laying hens

Alterations in the gut microbiota of Eimeria infected broiler chickens fed diets supplemented with varying levels of dietary calcium and phosphorus, along with 25-hydroxycholecalciferol

The purpose of the study was to investigate the effects of the reduced dietary calcium (Ca) and phosphorus (P) level and supplementation of 25-hydroxycholecalciferol (25-OHD3) on the expression of vitamin D receptor (VDR) and antimicrobial peptides and gut microbiota of broiler chickens with/without Eimeria challenge. A total of 576 fourteen-day-old broiler chicks were randomly allocated according to a 2 × 2 × 2 factorial design with main effects including Eimeria challenging (125,000 Eimeria acervulina, 25,000 Eimeria maxima, and 25,000 Eimeria tenella), dietary Ca and P levels (0.84% Ca and 0.42% available P or 0.64% Ca and 0.22% available P), and supplementation of 25-OHD3 (3,000 IU/kg) of 6 replicates. Three-way ANOVA was performed, and the effects of 3 main factors and their interactions were investigated. The reduced dietary Ca and P level downregulated cathelicidins 3 (CATH3) in the upper jejunum in the Eimeria challenging condition (interaction; P < 0.05). The reduced dietary Ca and P level decreased the relative mRNA expression of jejunal avian beta defensin 5 (AvBD5) in the Eimeria challenging condition (interaction; P < 0.05). The reduced dietary Ca and P level tended to decrease the relative mRNA expression of jejunal AvBD9 in the Eimeria challenging condition (interaction; P = 0.051). The reduced dietary Ca and P level decreased observed features (alpha diversity parameter for richness) in the upper jejunal microbiota in the Eimeria challenging condition (interaction; P < 0.05). The supplementation of 25-OHD3 decreased the relative abundance of the phylum Bacteroidetes (P < 0.05) and increased the relative abundance of the family Ruminococcaceae (P < 0.05) in the cecal digesta. The supplementation of 25-OHD3 decreased the serum endotoxin level in the Eimeria challenging condition (interaction; P < 0.05). Therefore, the reduced dietary Ca and P level modulated the upper jejunal microbiota via modulating the expression of antimicrobial peptides, and the supplementation of 25-OHD3 favorably modulated the cecal microbiota in broiler chickens with/without Eimeria challenge.

CAMKK2-AMPK axis endows dietary calcium and phosphorus levels with regulatory effects on lipid metabolism in weaned piglets

BackgroundIn the realm of swine production, optimizing body composition and reducing excessive fat accumulation is critical for enhancing both economic efficiency and meat quality. Despite the acknowledged impact of dietary calcium (Ca) and phosphorus (P) on lipid metabolism, the precise mechanisms behind their synergistic effects on fat metabolism remain elusive.ResultsResearch observations have shown a decreasing trend in the percentage of crude fat in carcasses with increased calcium and phosphorus content in feed. Concurrently, serum glucose concentrations significantly decreased, though differences in other lipid metabolism-related indicators were not significant across groups. Under conditions of low calcium and phosphorus, there is a significant suppression in the expression of FABPs, CD36 and PPARγ in the jejunum and ileum, leading to inhibited intestinal lipid absorption. Concurrently, this results in a marked increase in lipid accumulation in the liver. Conversely, higher levels of dietary calcium and phosphorus promoted intestinal lipid absorption and reduced liver lipid accumulation, with these changes being facilitated through the activation of the CAMKK2/AMPK signaling pathway by high-calcium-phosphorus diets. Additionally, the levels of calcium and phosphorus in the diet significantly altered the composition of liver lipids and the gut microbiota, increasing α-diversity and affecting the abundance of specific bacterial families related to lipid metabolism.ConclusionThe evidence we provide indicates that the levels of calcium and phosphorus in the diet alter body fat content and lipid metabolism by modulating the response of the gut-liver axis to lipids. These effects are closely associated with the activation of the CAMKK2/AMPK signaling pathway.

Development of the mineralisation of individual bones and bone regions in replacement gilts according to dietary calcium and phosphorus

Skeleton bones, distinguished by trabecular and cortical bone tissue content, exhibit varied growth and composition, in response to modified dietary calcium and phosphorus levels. The study investigated how gilts adapt their individual bone and bone region mineralisation kinetics in response to changing intake of Ca and P. A total of 24 gilts were fed according to a two-phase (Depletion (D) 60–95 and Repletion (R) 95–140 kg BW, respectively). During the D phase, gilts were fed either 60% (D60) or 100% (D100) of the estimated P requirement. Subsequently, during the R phase, half of the gilts from each D diet were fed either 100% (R100) or 160% (R160) of the estimated P requirement according to a 2 × 2 factorial arrangement. Bone mineral content (BMC) was assessed in the whole body, individual bones (femur and lumbar spine L2–L4), and bone regions (head, front legs, trunk, pelvis, femur, and hind legs) every 2 weeks using dual-energy X-ray absorptiometry (DXA). At 95 kg BW, gilts fed D60 showed reduced BMC and BMC/BW ratio in all studied sites compared to those fed D100 (P < 0.001). During the depletion phase, the allometric BW-dependent regressions slopes for BMC of D100 gilts remained close to 1 for all sites and did not differ from each other. In contrast, the slopes were lower in D60 gilts (P < 0.05), with an 18% reduction in the whole body, except for the front and hind legs, femur, and pelvis, which exhibited higher reductions (P < 0.05). At 140 kg BW, BMC and BMC/BW ratio of all studied sites were similar in gilts previously fed D60 and D100, but higher in R160 than in R100 gilts (P < 0.05), except for front and hind legs. During the repletion phase, the allometric BW dependent regressions slopes for BMC were lower (P < 0.05) in R100 than in R160 gilts (for whole body −10%; P < 0.01) except for front and hind legs, femur, and pelvis. In conclusion, bone demineralisation and recovery followed similar trends for all measured body sites. However, the lumbar spine region was most sensitive whereas the hind legs were least sensitive. These data suggest that using bone regions such as the head and forelegs that can be collected easily at the slaughterhouse may be a viable alternative to whole body DXA measurement.

Dietary Phosphorus Levels Influence Protein-Derived Uremic Toxin Production in Nephrectomized Male Rats.

Gut microbiota-derived uremic toxins (UT) accumulate in patients with chronic kidney disease (CKD). Dietary phosphorus and protein restriction are common in CKD treatment, but the relationship between dietary phosphorus, a key nutrient for the gut microbiota, and protein-derived UT is poorly studied. Thus, we explored the relationship between dietary phosphorus and serum UT in CKD rats. For this exploratory study, we used serum samples from a larger study on the effects of dietary phosphorus on intestinal phosphorus absorption in nephrectomized (Nx, n = 22) or sham-operated (sham, n = 18) male Sprague Dawley rats. Rats were randomized to diet treatment groups of low or high phosphorus (0.1% or 1.2% w/w, respectively) for 1 week, with serum trimethylamine oxide (TMAO), indoxyl sulfate (IS), and p-cresol sulfate (pCS) analyzed by LC-MS. Nx rats had significantly higher levels of serum TMAO, IS, and pCS compared to sham rats (all p < 0.0001). IS showed a significant interaction between diet and CKD status, where serum IS was higher with the high-phosphorus diet in both Nx and sham rats, but to a greater extent in the Nx rats. Serum TMAO (p = 0.24) and pCS (p = 0.34) were not affected by dietary phosphorus levels. High dietary phosphorus intake for 1 week results in higher serum IS in both Nx and sham rats. The results of this exploratory study indicate that reducing dietary phosphorus intake in CKD may have beneficial effects on UT accumulation.

Nutritional and physiological responses to dietary phosphorus levels and phytase in pullets and laying hens

The objective of this study was to determine the effects of dietary available phosphorus (P) levels and dietary phytase added into the very low-P diet on the performance, mineral balance, odor emission, and stress responses in growing pullets and laying hens during 13 to 32 wk of age. One hundred sixty-eight pullets (Hy-Line Brown) were randomly assigned into 1 of 4 dietary treatments with 7 replicates of 6 birds each. Experimental diets were formulated to contain 3 graded P levels at 0.25, 0.35, and 0.45% during 13 to 15 wk (phase 1), 0.25, 0.35, and 0.45% during 16 to 18 wk (phase 2), and 0.20, 0.30, and 0.40% during 19 to 32 wk (phase 3). In addition, dietary phytase (500 FTU/kg matrix values) was added into the very low-P diets (0.20% during 13-15 wk, 0.25% during 16-18 wk, and 0.20% during 19-32 wk) to meet the nutritional adequacy with standard P diets. In all phases, decreasing dietary P levels did not affect (P > 0.05) growth, laying performance, and egg qualities. Decreasing dietary P levels linearly increased the relative duodenal and oviduct weights (P < 0.05), and quadratically increased the relative ovary weight in pullets (P = 0.016). Dietary phytase lowered (P = 0.021) the relative duodenal weight compared with the very low-P diet. Tibia breaking strength and tibia Mg contents in pullets were linearly lowered (P < 0.05) as dietary P levels decreased. Dietary phytase tended to increase (P = 0.091) tibia breaking strength and significantly increased (P = 0.025) tibia Mg content compared with the very low-P diet. Dietary P levels and dietary phytase affected (P < 0.05) ileal crypt depth and ileal villus height: crypt depth ratio in pullets. Decreasing dietary P levels linearly decreased (P < 0.01) crude fat digestibility and P excretion in both pullets and laying hens. Dietary phytase reversed (P < 0.05) the very low-P diet-mediated decrease of crude fat digestibility in pullets and laying hens. Dietary P levels and dietary phytase affected (P < 0.05) odor emission including ammonia in pullets and total volatile fatty acids in laying hens. Finally, lowering dietary P levels increased (P < 0.01) yolk corticosterone concentrations and the increased corticosterone concentration by the very low-P diet was reversed by dietary phytase. Collectively, our study shows that decreasing dietary P levels induced nutritional and physiological responses in pullets and laying hens and these P-mediated negative effects were mitigated by dietary phytase.

Impacts of dietary phosphorus level on growth, antioxidant capacity and immunity in juvenile hybrid grouper (Epinephelus fuscoguttatus ♀ × E. lanceolatus ♂) fed with high-lipid diets

The study was designed to evaluate the effect of available phosphorus on growth performance, antioxidant capacity and non-specific immunity in hybrid grouper (♀ Epinephelus fuscoguttatus × ♂ E. lanceolatus) fed with high-lipid diets. Juvenile fish (8.06 ± 0.02 g) were subjected to six different dietary treatments over a period of eight weeks. These treatments consisted of diets (16% lipid level and 45% protein level) containing 0.3%, 0.58%, 0.67%, 0.76%, 0.85% and 0.94% available phosphorus (MCP), designated P1 (control), P2, P3, P4, P5 and P6, respectively. The results showed that (1) P1 group had suppressed final weight, weight gain and specific growth rate, while the other phosphorus experimental groups had significantly higher growth performance than the P1 group (P < 0.05). (2) With increasing phosphorus level, serum total antioxidant capacity (T-AOC), superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPX) enzyme activities increased significantly (P < 0.05). (3) With the increase in dietary phosphorus level, the reactive oxygen species (ROS) content in the liver was significantly decreased (P < 0.05). And the malondialdehyde (MDA) content was significantly decreased, while SOD, CAT, lysozyme (LYS), alkaline phosphatase (AKP), aspartate transaminase (AST) enzyme activities, T-AOC and IgM contents were significantly increased (P < 0.05) (4 The expression of antioxidant genes, such as hsp70, hsp90, sod, cat, gpx, were significantly higher in the appropriate phosphorus level groups than P1 group (P < 0.05), meanwhile the expression of proinflammatory factors, such as il6, il8, tnfα, was significantly reduced (P < 0.05). (6) In the attack experiment, the survival rate of P4 group was the highest, and the survival rate of P2 and P1 groups were the lowest. In conclusion, the appropriate addition of phosphorus can improve growth, antioxidant capacity of fish and disease resistance, and we recommend its addition at 0.67% to 0.77% in diet.

Physiological Response of Spotted Seabass (Lateolabrax maculatus) to Different Dietary Available Phosphorus Levels and Water Temperature: Changes in Growth, Lipid Metabolism, Antioxidant Status and Intestinal Microbiota.

A 10-week growth experiment was conducted to assess the physiological response of spotted seabass (Lateolabrax maculatus) raised at moderate (27 °C) and high temperatures (33 °C) to different dietary available phosphorus (P) levels. Five diets with available P levels of 0.35, 0.55, 0.71, 0.82 and 0.92% were formulated, respectively. A water temperature of 33 °C significantly decreased growth performance and feed utilization, and increased oxidative stress and lipid deposition of spotted seabass compared with 27 °C. A second-order polynomial regression analysis based on weight gain (WG) showed that the available P requirement of spotted seabass raised at 27 °C and 33 °C was 0.72% and 0.78%, respectively. The addition of 0.71-0.82% P to the diet improved the growth performance, feed utilization, and antioxidant capacity of spotted seabass and alleviated the excessive lipid deposition compared with the low-P diet (0.35% P). Moreover, the addition of 0.71-0.92% P to diets increased the diversity of intestinal microbiota and the relative abundance of Lactococcus lactis and decreased the relative abundance of Plesiomonas compared with the low-P diet. Thus, dietary supplementation with 0.71-0.82% P improved the growth performance, antioxidant capacity and microbial composition of spotted seabass, and alleviated the disturbance of lipid metabolism caused by high temperature or low-P diet.

Effect of 25-hydroxycholecalciferol supplementation with different dietary available phosphorus levels for broilers

ABSTRACT 1. Based on the hypothesis that 25-hydroxycholecalciferol (25-OH-D3) inclusion would optimise dietary mineral digestibility and ameliorate growth performance and bone mineralisation in available phosphorus (AvP) deficient-fed broilers, a trial was conducted to evaluate its effect on diets with different levels of AvP. 2. Broilers aged 1–21 d were randomly assigned one of the eight treatments, consisting of four dietary levels of AvP (0.45%, 0.42%, 0.39%, and 0.36%) and with or without supplementation with 25-OH-D3 at 69 μg/kg of feed. All diets contained 100 µg/kg of vitamin D3 (cholecalciferol). 3. The addition of 25-OH-D3 resulted in higher feed intake and body weight gain, and lower FCR (P < 0.05) compared to non-supplemented diets, whereas AvP levels had a quadratic effect only on feed intake. There were no interactions between treatment factors. 4. Increasing AvP levels linearly reduced the ileal digestibility of Ca and P (P < 0.01) and supplementing 25-OH-D3 increased both Ca and P ileal digestibility (P < 0.05), without any interactions observed for ileal digestibility. 5. There was an interaction, whereby 25-OH-D3 inclusion increased serum metabolites in broilers fed 0.36% to 0.42% AvP compared to the non-supplemented diets (P < 0.001), whereas, at 0.45% AvP, diets with or without 25-OH-D3 had similar results. 6. The P content in bone linearly increased in line with AvP levels (P < 0.05) and supplementation of 25-OH-D3 increased ash bone content (P < 0.001). 7. Broilers can benefit from 25-OH-D3 supplementation combined with cholecalciferol with regard to Ca and P utilisation and vitamin D status, allowing for a reduction of dietary AvP levels down to 0.36% without impairing growth performance or bone status.

Influence of dietary phosphorus on orthophosphate accumulation in recirculating aquaculture systems with rainbow trout (Oncorhynchus mykiss)

Dietary phosphorus (P) levels affect the excretion of orthophosphate (PO4-P) from fish. Since most recirculating aquaculture systems (RAS) do not specifically remove PO4-P within the recirculating loop, dietary P levels may influence PO4-P concentrations in RAS water. A feeding trial was performed in freshwater RAS, aiming to determine the relationship between dietary P levels and PO4-P accumulation in RAS water, and to examine potential effects of dietary P levels on microbial activity and abundance in RAS water given that P is an essential mineral for all microorganisms. Three diets with 1.49% (HiP), 1.20% (MeP), and 0.89% (LoP) total P, respectively, were each fed to triplicate pilot-scale RAS with juvenile rainbow trout (Oncorhynchus mykiss) for five weeks, applying a daily feed loading of 1.67 kg feed/m3 make-up water. Digestible dietary P levels correlated significantly with the PO4-P concentrations in RAS water at the end of the trial, while no similar correlations with microbial abundance or activity were observed. Nitrate-N concentrations measured by the end of the trial matched predicted equilibrium concentrations. In contrast, measured PO4-P concentrations were approximately 40 – 50% lower than predicted regardless of diets, suggesting that PO4-P was likely utilized by RAS microbes. We therefore speculate whether lowering dietary P levels could become an effective tool for microbial management in RAS.

High Dietary Phosphorus Is Associated with Increased Breast Cancer Risk in a U.S. Cohort of Middle-Aged Women.

Research has shown that high amounts of dietary phosphorus that are twice the amount of the U.S. dietary reference intake of 700 mg for adults are associated with all-cause mortality, phosphate toxicity, and tumorigenesis. The present nested case-control study measured the relative risk of self-reported breast cancer associated with dietary phosphate intake over 10 annual visits in a cohort of middle-aged U.S. women from the Study of Women's Health Across the Nation. Analyzing data from food frequency questionnaires, the highest level of daily dietary phosphorus intake, >1800 mg of phosphorus, was approximately equivalent to the dietary phosphorus levels in menus promoted by the United States Department of Agriculture. After adjusting for participants' energy intake, this level of dietary phosphorus was associated with a 2.3-fold increased risk of breast cancer incidence compared to the reference dietary phosphorus level of 800 to 1000 mg, which is based on recommendations from the U.S. National Kidney Foundation, (RR: 2.30, 95% CI: 0.94-5.61, p = 0.07). Despite the lack of statistical significance, likely due to the small sample size of the cohort, the present nested case-control study's clinically significant effect size, dose-response, temporality, specificity, biological plausibility, consistency, coherence, and analogy with other research findings meet the criteria for inferred causality in observational studies, warranting further investigations. Furthermore, these findings suggest that a low-phosphate diet should be tested on patients with breast cancer.

Effects of dietary α-ketoglutarate on the growth performance, digestive enzymes, tor signaling pathway and intestinal microbiota of juvenile mirror carp (Cyprinus carpio) fed low phosphorus diets

The present study evaluated the effects of dietary α-ketoglutarate (AKG) on the growth performance, digestive enzymes, target of rapamycin (tor) signaling pathway and intestinal microbiota of juvenile mirror carp (Cyprinus carpio) fed low phosphorus diets. An eight week 2 × 3 two-factorial experiment was conducted to investigate the interaction between AKG levels at 0 or 0.6%, and dietary phosphorus levels at 0.27%, 0.55% or 0.76%. The results showed that the final body weight (FBW) and weight growth rate (WGR) were significantly improved and the feed conversion ratio (FCR) was significantly decreased by the dietary AKG or phosphorus (P < 0.05). The crude ash and phosphorous content were significantly increased with increasing available phosphorus supplement from 0.27% to 0.76%, whereas crude lipid was decreased as dietary phosphorus levels increased (P < 0.05). Fish fed a diet supplemented with 0.6% AKG showed a significant increase in crude protein, crude ash and phosphorous content compared to the diet without AKG group (P < 0.05). The mRNA expression of IIb sodium-dependent phosphate cotransporter (NaPi-IIb) was decreased by dietary AKG or phosphorus (P < 0.05).The activities of trypsin was significantly improved by dietary AKG or phosphorus (P < 0.05). The mRNA expression of tor, insulin growth factor I (igfI) and growth hormone (gh) were significantly increased by dietary AKG or phosphorus (P < 0.05). The richness estimate of Ace and Chao, and the diversity estimators of Simpson were significantly decreased with increasing phosphorus levels from 0.27% to 0.55% (P < 0.05). Compared with the 0.27% phosphorus group, the abundance of Fusobacteriota and Bacteroidota were relatively increased and the abundance of Proteobacteria, Actinobacteriota and Cyanobacteria were relatively decreased in 0.27% phosphorus added 0.6% AKG group. The abundance of Fusobacteriota and Actinobacteriota in 0.27% phosphorus group was relatively lower than that in 0.55% phosphorus group. On the contrary, the abundance of Firmicutes, Bacteroidota and Cyanobacteria in 0.27% phosphorus group was relatively higher than that in 0.55% phosphorus groups. These results indicated that dietary supplementation with 0.6% AKG could improve growth performance by increasing the activities of trypsin and promoting the formation of beneficial intestinal microbiota, and the tor, gh/igf-I gene expression in liver of mirror carp fed low phosphorus diets.

Influence of Dietary Phosphorus on the Growth, Feed Utilization, Proximate Composition, Intestinal Enzymes, and Oxidation Resistance of Sea Cucumber Apostichopus japonicus.

Six experimental diets (crude protein 12.58%, crude fat 1.93%, and total energy 10.72 kJ/kg) containing 0.24%, 0.37%, 0.51%, 0.62%, 0.77%, and 0.89% phosphorus were formulated to evaluate dietary phosphorus requirement for sea cucumber Apostichopus japonicus. The feeding trial was conducted in 18 fiberglass tanks (220 L) for 63 days. Each diet was randomly assigned to triplicate tanks of 50 sea cucumbers (9.99 g) and fed once daily. With the increase of dietary phosphorus level, weight gain (WG), specific growth rate (SGR), daily feed intake (DFI), feces production ratio, the activities of amylase, alkaline phosphatase, phosphofructokinase, succinate dehydrogenase, and glutathione peroxidase as well as the contents of glutathione and glutathione oxidized significantly increased and then decreased afterwards (P < 0.05). A. japonicus fed diet with 0.63%, 0.63%, and 0.55% dietary phosphorus was estimated to yield the highest WG (11.39 g), SGR (1.09%/d), and DFI (2.55%/d) according to the quadratic regression analysis of WG, SGR, and DFI against dietary phosphorus level, respectively. The apparent digestibility of dry material and energy followed an opposite tendency. Feed efficiency, the contents of whole-body phosphorus, initially increased and then plateaued, fitting piecewise-linear models with breakpoint at 0.57% and 0.55% dietary phosphorus. Daily phosphorus intake, pyruvate kinase activity, and the ratio of glutathione and glutathione oxidized increased (P < 0.05) but the apparent digestibility of phosphorus, the activities of alkaline protease, aspartate transaminase, and phosphoenolpyruvate carboxykinase decreased (P < 0.05), responding to the increasing dietary phosphorus. Considering the present results, the optimal dietary phosphorus for A. japonicus is 0.57-0.63%.

Optimal Dietary Protein/Energy Ratio and Phosphorus Level on Water Quality and Output for a Hybrid Grouper (Epinephelus lanceolatus ♂ × Epinephelus fuscoguttatus ♀) Recirculating Aquaculture System

In a recirculating aquaculture system (RAS), feed is critical to the growth of fish and is the main source of nutrient pollutants in aquaculture water. An eight-week feeding trial was conducted to investigate the role of feed on the growth efficiency of hybrid grouper (Epinephelus lanceolatus ♂ × Epinephelus fuscoguttatus ♀) and water quality in a RAS. Five commercial feeds with different respective dietary protein/energy (P/E) ratios and available phosphorus levels were selected (LNLP, 31.97 g/MJ, 0.96%; LNMP, 32.11 g/MJ, 1.54%; MNLP, 36.26 g/MJ, 0.98%; MNMP, 36.53 g/MJ, 1.58%; and HNP, 41.54 g/MJ, 1.97%). The results showed that HNP had the highest growth efficiency and MNLP provided the best economic benefit. The trend in water quality within 6 h after feeding was similar among the five groups. The relative concentrations of ammonia nitrogen, total nitrogen, active phosphate, and total phosphorus reached a maximum 2 h after feeding, and the relative concentration of nitrite reached a maximum 1 h after feeding. The high P/E ratio feed increased the concentrations of total ammonia nitrogen and nitrite nitrogen. The total ammonia nitrogen concentration in HNP was much higher than those in the other treatments. The dietary P/E ratio had no significant effect on total nitrogen concentration. High dietary phosphorus levels increased the total phosphorus concentration in the water, but no significant effect on the active phosphate concentration was observed. Considering the growth efficiency, economic benefit, and water quality, it can be concluded that MNLP is the most suitable feed for RAS breeding hybrid grouper. The results of this study supplement the gap on the effects of feed on RAS water quality and provide data support for the sustainable development of RAS industry.

Long-term effects of dietary calcium and phosphorus level, and feed form during rearing on egg production, eggshell quality, and bone traits in brown laying hens from 30 to 89 wk of age

The effects of feeding strategies during rearing (0-16 wk) of brown laying hens on mid and end laying performance (30-89 wk) were studied. The rearing feeding strategies followed a 3×2 factorial arrangement with feed form; mash with inclusion of 3% finely ground wheat straw (MWS), crumbles with inclusion of 3% finely ground wheat straw (CWS), and crumbles with inclusion of 3% unground oat hulls as fiber sources (COH) at 2 dietary Ca and P levels (high or low Ca-P). Feed conversion ratio improved with COH and MWS compared with CWS from 30 to 59 wk. Rate of lay and egg mass production showed a feed form×Ca-P interaction from 60 to 89 wk. Low Ca-P led to a higher egg production, but only when COH and MWS were fed. BW at 89 wk was higher with CWS compared to COH and MWS. BW uniformity was better with COH compared to MWS at 51 wk and both CWS and MWS at 67 wk. Tibia characteristics were not clearly affected by treatment, although there was a feed form×Ca-P interaction on compression at 89 wk, where compression was lower with MWS and low vs. high Ca-P. Low Ca-P during rearing led to higher eggshell thickness, compared to high Ca-P at 45 wk of age, but breaking strength was lower with low vs. high Ca-P at 75 wk. Although eggshell quality was affected by Ca-P and there were some interactions with feed form at some ages, the effect was not consistent. There was no clear relationship between eggshell quality and tibia characteristics. It was concluded that feeding low Ca-P in combination with COH and MWS during the rearing period positively affects egg production during late lay. Also, dietary Ca-P levels, compared to commercial practice, can be lowered during rearing, as this will not affect eggshell quality and bone mineralization at later ages.

Increasing Phosphorus Intake Reduces Urinary Concentrations of Magnesium and Calcium in Adult Ovariectomized Cats Fed Purified Diets

We assessed the phosphorus requirement of adult cats and the relationship between phosphorus intake and the fecal and urinary excretion of calcium, magnesium and phosphorus. Female cats (ovariectomized at the onset of sexual maturity) were fed purified diets containing 4.6, 9.2, 18.4 or 27.7 mmol phosphorus/MJ in a 4 × 4-wk crossover study. During the experiment, balance studies were performed and blood samples were taken. A dietary level of 4.6 mmol phosphorus/MJ was found to be sufficient to maintain phosphorus balance and normal plasma concentrations of phosphorus in the adult ovariectomized cats. Increasing levels of dietary phosphorus in the form of NaH2PO4·2H2O caused lower urinary pH values, lower urinary concentrations of calcium and magnesium, and higher urinary concentrations of phosphorus. When dietary levels of phosphorus were raised, the percentage of apparent absorption of magnesium was lower, whereas that of phosphorus was higher. Although it could be predicted that dietary phosphorus levels higher than the National Research Council recommendation of 9.2 mmol/MJ markedly reduced urinary struvite saturation, these higher levels are discouraged because they are associated with lower plasma phosphorus concentrations and creatinine clearance.

Age at Sexual Maturity Influences the Response of Single Comb White Leghorn Publlets to Marginal and Low Levels of Dietary Phosphorus

This study was designed to determine the differences in response of early-maturing (EM) and latematuring (LM) Single Comb White Leghorn pullets within a flock to marginal or low dietary phosphorus. Various levels of dietary phosphorus were fed to EM and LM Leghorn puliets from 18 wk of age until the age of peak egg production (24 wk). The dietary phosphorus levels were 0.40, 0.45, 0.50, 0.55 and 0.70 g total phosphorus (tP)/100 g diet, corresponding to calculated available phosphorus values of 0.18, 0.23, 0.28, 0.33 and 0.48 g/100 g, respectively. At 0.70 and 0.55 g tP/100 g, the plasma inorganic phosphorus, Ca++ and urine calcium concentrations did not differ between EM and LM puliets, whereas LM pullets had a better bone status than EM pullets as reflected by bone mineral content, bone density and bone breaking strength. As dietary phosphorus was lowered from 0.55 to 0.4 g tP/100 g, the plasma concentration of inorganic phosphorus dropped and that of Ca++ increased at greater rates in LM pullets than in EM pullets. The magnitude of decline in bone status was also greater in LM than in EM puliets when dietary phosphorus was lowered from 0.55 to 0.40 g tP/100 g. The maximum incidences of osteoporosis and mortality were observed in LM pullets fed 0.40 g tP/100 g, followed by LM pullets fed 0.45 g tP/100 g diet. We conclude that when early layer diets contain marginal or low levels of phosphorus, the severity of adverse effects are greater in LM pullets than in EM pullets.

The impact of the interaction between dietary total phosphorus level and efficacy of phytase on the performance of growing-finishing pigs

Two experiments were conducted to investigate the interaction between dietary total phosphorus (P) level and phytase on the performance of growing-finishing pigs. In experiment 1, a total of 96 growing pigs [Duroc × Landrace × Yorkshire (barrows, initial body weight (BW) = 39.1 ± 0.5 kg), 8 pigs per treatment] were used in a 5-d total fecal and urine collection study to determine the apparent total tract digestible (ATTD) P release value of phytase in 2 dietary standardized total tract digestible (STTD) P levels (1.49 vs 2.87 g/kg of STTD P) with 0, 250, 500, 750, 1000, and 1250 FTU/kg of phytase. The results indicated that there was an interaction between P level and phytase in the determination of coefficient of apparent total tract digestibility of P (P < 0.01). The determined P release curves were STTD P = −1.4 phytase2 × 10−6 + 20.8305 phytase × 10−3 + 6.88392 × 10−2, R² = 0.9766 [1] in low-P diets, and STTD P = −1.2 phytase2 × 10−6 + 20.2754 phytase × 10−3 + 1.86325 × 10−2, R² = 0.9965 [2] in high-P diets. In experiment 2, a total of 1344 growing pigs [Duroc × Landrace × Yorkshire (initial BW = 69.4 ± 0.6 kg), 28 pigs per pen] were used in a 35-d growth performance study. The study had 4 dietary treatments which included low-P (1.0 g/kg of STTD P) diet group, high-P (1.9 g/kg of STTD P) diet group, low-P diet + 1100 FTU/kg phytase group, and high-P diet + 250 FTU/kg phytase group. The two treatments with phytase were formulated to the same STTD P level using the P release value of phytase determined by equation [1] from Experiment 1. The results showed that the treatment with 1100 FTU/kg phytase had greater gain to feed ratio compared to the treatment with 250 FTU/kg phytase, 1.0 g/kg total STTD P group and 1.9 g/kg total STTD P group (P < 0.05). In conclusion, the determination of P release of phytase may be impacted by the total P level in the diet. The P release value determined in low-P diets may not be accurate for the diet formulation when dietary total P level is greater.

Evaluation of Phosphorus Storage and Performance of Broilers Using Phytase Synthetic Enzyme.

Phytic acid is a stored form of phosphorus in cereals, 65 to 70% of phosphorus in plant sources is phytate, and broilers are only able to use part of the phosphorus in plant sources. To meet the needs of chickens, it is necessary to use other artificial resources, which not only impose part of the cost of the breeding period because of its presence in the manure but is one of the factors polluting the environment. This study aimed to use different levels of phytase enzyme to reduce dietary phosphorus levels. 600 Ross 308 broilers were used in this experiment with five treatments and six replications, and in each replication, 20 chickens were used in a completely randomized design (CRD). Experimental treatments include 1) basal diet (control) 2) basal diet with 15% less phosphorus 3) basal diet with 15% less phosphorus + 1250 (FTU) phytase enzyme 4) basal diet with 15% less phosphorus + 2500 (FTU) phytase enzyme 5) basal diet with 15% less phosphorus + 5000 (FTU) phytase enzyme. The evaluated traits included weekly feed intake, weekly weight gain, feed conversion ratio, carcass characteristics, ash, calcium, and bone phosphorus. The use of phytase enzyme in different diets had no significant effect on food intake, weight gain, and feed conversion ratio (P>0.05). However, the use of phytase in different diets significantly affected the percentage of Gizzard, Heart, Liver, Proventriculus, and Spleen (P<0.05). The most changes were the increase in the ratio of feed intake and weight gain in the fourth week compared to the third week so that the changes in the ratio of feed intake ranged from 1.85 to 1.91, and this ratio for weight gain also ranged from 3.12 to 3.86 was recorded, and the lowest feed conversion ratio was obtained at the same age. The percentage of raw ash in broiler chickens was significantly increased by adding dietary phytase. The lowest amount of ash, calcium, and phosphorus belonged to the second group (diets with low phosphorus and no enzyme). The difference between the other groups and the control was not significant. Feed intake, weight gain, and feed conversion ratio with the addition of phytase enzyme were not affected by phosphorus reduction and had no significant effect on carcass characteristics. Environmental pollution can be prevented by reducing the level of dietary phosphorus and reducing excreted phosphorus.

Mucosal phosphatase activity, phytate degradation, and mineral digestibility in 6-week-old turkeys and broilers at different dietary levels of phosphorus and phytase and comparison with 3-week-old animals

Female turkeys (B.U.T. 6) and broilers (Ross 308) were compared at 6 wk of age to evaluate the effects of species, dietary P, Ca, and phytase levels on myo-inositol hexakisphosphate (InsP6) degradation along the digestive tract, gut mucosal phosphatase activity, P and Ca digestibility, and myo-inositol concentrations in the digesta and blood. The environmental conditions and experimental corn-soybean meal-based diets were the same for both species. Four diets with either combination of 2 levels of P and Ca (CaP-: 4.0 g P/kg, 5.4 g Ca/kg and CaP+: 6.0 g P/kg, 8.0 g Ca/kg) and 2 levels of phytase supplementation (0 and 1,500 FTU/kg) were fed to the animals for 7d at their sixth wk of age. Each diet was randomly assigned to 6 pens per species, with 10 birds each. After slaughter, blood, digesta from the crop, gizzard, duodenum, lower ileum, and jejunal mucosa were collected. Endogenous mucosal phosphatase activity in the jejunum was higher in turkeys than in broilers. Prececal InsP6 disappearance was also higher in turkeys than in broilers when phytase was not supplemented. Phytase supplementation led to a higher prececal InsP6 disappearance in broilers than in turkeys, likely due to different crop conditions such as moisture content. However, prececal P digestibility was higher in turkeys than broilers. Different relationships between myo-inositol concentration in the ileum digesta and blood were found, depending on the species. A comparison of the results with those obtained in 3-wk-old birds of a companion study showed that in diets with low Ca and P levels, prececal InsP6 disappearance increased with age in turkeys, but not in broilers. This coincided with changes in the conditions of the digestive tract, such as the water content in the crop, gizzard pH, and mucosal phosphatase activity. In conclusion, occurrence of differences in phytate degradation between turkeys and broilers, fed the same feed, depended on age and can be explained by different physiological development of the digestive tract.