Identification of the Key Molecular Drivers of Phosphorus Utilization Based on Host miRNA-mRNA and Gut Microbiome Interactions

Phosphorus is an essential mineral for all living organisms and a limited resource worldwide. Variation and heritability of phosphorus utilization (PU) traits were observed, indicating the general possibility of improvement. Molecular mechanisms of PU, including host and microbial effects, are still poorly understood. The most promising molecules that interact between the microbiome and host are microRNAs. Japanese quail representing extremes for PU were selected from an F2 population for miRNA profiling of the ileal tissue and subsequent association with mRNA and microbial data of the same animals. Sixty-nine differentially expressed miRNAs were found, including 21 novel and 48 known miRNAs. Combining miRNAs and mRNAs based on correlated expression and target prediction revealed enrichment of transcripts in functional pathways involved in phosphate or bone metabolism such as RAN, estrogen receptor and Wnt signaling, and immune pathways. Out of 55 genera of microbiota, seven were found to be differentially abundant between PU groups. The study reveals molecular interactions occurring in the gut of quail which represent extremes for PU including miRNA-16-5p, miR-142b-5p, miR-148a-3p, CTDSP1, SMAD3, IGSF10, Bacteroides, and Alistipes as key indicators due to their trait-dependent differential expression and occurrence as hub-members of the network of molecular drivers of PU.

Inferring relationships between Phosphorus utilization, feed per gain, and bodyweight gain in an F2 cross of Japanese quail using recursive models

Phosphorus utilization (PU) has received considerable attention in poultry nutrition. However, reliable estimates of genetic parameters for PU and related traits have largely not been reported until now; however, these are needed to assess whether selection for an improved PU would result in selection response. A large Japanese quail F2 cross was generated and 888 F2 individuals were phenotyped for PU, bodyweight gain (BWG), and feed per gain (F:G). Because it can reasonably be assumed that the interrelationships between these traits are complex, structural equation models were used. The structural coefficient λij describes the rate of change of trait I with respect to trait j for a model with a recursive effect of trait j on trait i Three recursive structural coefficients (λF:G,PU,λBWG,PU,λBWG,F:G) were selected a priori based on biological knowledge. The model was fitted using ASReml software. Standard errors of estimated variance components and genetic parameters were approximated using the delta method. The heritability of PU, F:G, and BWG were 0.136, 0.118, and 0.092. The structural coefficient[Formula: see text]indicates that an increase in PU leads to reduced and thus improved F:G. The estimate[Formula: see text]indicates that improved F:G leads to an increase in BWG. The overall effect of PU on BWG was[Formula: see text]i.e. an increase in PU of 1% leads to an increase of BWG of 0.374 g in the data collection period, which spanned five days. The phenotypic and genetic correlations were negative between PU and F:G as well as between BWG and F:G and were positive between PU and BWG. These correlations are driven by direct genetic effects (pleiotropic genes or genes being in linkage disequilibrium) as well as by indirect genetic effects (genes affecting trait j affected indirectly trait i). The application of structural equation models contributed to our understanding of the complex biological relationship between PU, F:G, and BWG in quails. PU shows a heritability that is sufficient to achieve a selection response when breeding for this very-hard-to-measure trait.

Effects of high non-phytate phosphorus starter diet on subsequent growth performance and carcass characteristics of broiler chickens

The trial was performed to investigate the effects of different concentrations of non-phytate phosphorus (nPP) in the starter and grower (with phytase inclusion) periods on carcass characteristics, organ weight and weekly variations of growth performance in the grower period. Seven hundred and twenty-day-old male broiler chickens were randomly assigned to 12 treatments in a completely randomized design. Chickens received two dietary treatments (4.5 g/kg and 6 g/kg nPP) in the starter (0-21 days) and six experimental diets (4 g/kg, 3.1 g/kg, 2.3 g/kg and 2.3 g/kg + 1000 FTU/Kg of feed phytase, 1.5 g/kg, 1.5 g/kg nPP + 1000 FTU/Kg of feed phytase) in the grower period (22-42 days). Results showed that phytase inclusion in the second and third weeks of grower period could increase feed intake significantly. Also, decrease in the concentrations of nPP to 1.5 g/kg caused to decline body weight gain markedly. Moreover, there is a significant difference between 4.5 g/kg and 6 + 4 g/kg nPP (starter+grower) and 1.5 g/kg nPP. Phytase inclusion increased carcass yield and declined liver weight significantly. Dietary treatment of 4.5 + 1.5 g/kg nPP enhanced heart and liver weight markedly. It is concluded that starter diets with increased concentration of nPP (6 g/kg nPP) had no beneficial effects on growth performance in the starter and grower period in the total (0-42 days). Also, it is possible to decrease nPP concentration of grower diets to 1.5 and 2.3 g/kg with and without phytase inclusion respectively.

Genetic interrelationships among phosphorus, nitrogen, calcium, and energy bioavailability in a growing chicken population

A random-mating population was used to study the genetic interrelationship between phytate P (PPB), Ca (CaB), N (NB), and energy bioavailability (EB), BW at 4 wk of age, relative growth (RG), and feed conversion ratio (FCR). Heritability estimates for PPB, CaB, NB, and EB were 0.09, 0.13, 0.16, and 0.10, respectively, and those of BW, RG, and FCR were 0.66, 0.15, and 0.10, respectively. Genetic correlations between PPB and BW, and FCR were moderate and negative, suggesting that improvement in PPB will impair growth. The genetic correlations between PPB and CaB, and EB and RG were positive and moderate, indicating that improvement in PPB would also lead to improved CaB, EB, and RG. Energy bioavailability was positively correlated with CaB, NB, PPB, and BW. Even though the genetic correlation between EB and the other traits measured, except RG and FCR, ranged from low to moderate, improving the ability of birds to utilize caloric energy in the feed would consequently improve PPB as well as growth. Improving PPB would reduce the amount of P in excreta and provide an additional savings if exogenous phytase were not added to poultry feed. The genetic correlation between PPB and NB was low but positive, whereas NB had a positive genetic correlation with BW. Therefore, selecting on NB will result in positive correlated responses in BW and PPB. Improving PPB and NB will not only improve productivity, but also reduce the polluting effects of P and N on the environment.

Modeling of Parameters Affecting Phytate Phosphorus Bioavailability in Growing Birds

The current study was undertaken to establish a population from an unselected random-mating chicken population for the development of a model to predict factors that affect phytate P utilization in growing birds. A population was established from a mating of 40 male and 200 female chickens from the Athens Canadian randombred population. At 4 wk of age, birds were housed in individual metabolic cages and fed a diet containing 1.06% Ca, 0.35% total P, and 0.03% available P. After 3 d of acclimatization, feed consumption (FC) was measured and excreta produced in 3 consecutive d were collected. Individual 4-wk BW, BW gain (BWG), phytate P intake (PPI), inorganic P intake (IPI), Ca intake (CaI), N intake (NI), and energy intake (EI) during the 3 d excreta collection period were also measured. Feed conversion ratios (FCR) and relative growth rate were calculated. Phytate P bioavailability (PPB), Ca bioavailability (CaB), and N bioavailability (NB) were estimated from the disappearance of the nutrients during the passage of feed through the gastrointestinal tract. Energy bioavailability (EB) was measured by bomb calorimetry as the difference in the gross energy of the feed and the energy of the excreta. The major factors affecting PPB were CaB and EB for both sexes. In the males, BW contributed significantly to PPB. However, in the females, NB also contributed significantly to PPB. Faster growing birds tended to have a reduced retention time of feed compared with slow growing birds, and as a result utilized phytate P less. Birds that are able to utilize phytate P better are putatively able to release P for energy utilization. Therefore, the birds that were able to utilize phytate P better were also better energy utilizers.

Effects of microbial phytase supplementation on mineral utilization and serum enzyme activities in broiler chicks fed different levels of phosphorus

An experiment was conducted to study the effect of microbial phytase (Natuphos 500) supplementation in chicks (0 to 6 wk of age) fed different levels of nonphytate phosphorus (nPP) on performance, mineral retention, bone and plasma minerals and serum enzyme activities. Data were analyzed as a 2 x 2 factorial arrangement with two levels of nPP for age periods of 1-d-old to 3 wk (0.35 and 0.22%) and 3 to 6 wk (0.27 and 0.14%) and two levels of phytase (0 and 500 U/kg) in each period. A positive control, adequate in nPP and Ca without phytase, was used. The low-nPP diets caused a negative effect on the performance (P < 0.05) compared to the normalnPP diet. Phytase had a favorable effect on weight gain at 3 wk (P < 0.004) and 6 wk (P < 0.0475) of age and on feed consumption only at 3 wk (P < 0.0106). Feed efficiency was not affected at any stage by addition of phytase. Performances of chicks fed with 0.35 and 0.27% nPP and phytase were comparable to those obtained with the normal-nPP diets. Decreasing nPP content in the diet increased (P < 0.0001) P retention at 3 and 6 wk of age, increased Mg retention at 6 wk, and decreased (P < 0.0001) Ca and Zn retentions at 3 and 6 wk, respectively. Phytase supplementation increased (P < 0.0001) Ca, P, Mg, and Zn retention at 3 and 6 wk of age. Likewise, the decrease in nPP content in the diet caused a significant reduction of tibia ash (P < 0.0023) and Mg content (P < 0.0001) in tibia ash and reduced liver (P < 0.0240), spleen (P < 0.0176), and tibia (P < 0.0001) weights. Similarly, Ca (P < 0.0369) and Zn (P < 0.0181) contents in tibia ash were increased in response to decreasing nPP levels in the diet. Phytase supplementation increased tibia weight (P < 0.0019), tibia ash (P < 0.0021), and Mg (P < 0.0339) and Zn (P < 0.0353) concentrations and reduced (P < 0.0161) the relative liver weight. By decreasing nPP levels in the diet, plasma Ca (P < 0.0001), Mg (P < 0.0001) and Zn (P < 0.0048) concentrations, and alkaline phosphatase (ALP) activity (P < 0.0299) increased, and plasma P content (P < 0.0001), aspartate aminotransferase (AST) activity (P < 0.0001), and total protein (TP) content (P < 0.0050) were reduced. Phytase supplementation increased plasma P level (P < 0.0001) and serum AST activity (P < 0.0049), reduced plasma Ca (P < 0.0001) and Mg (P < 0.0050) contents, and reduced serum alanine aminotransferase (ALT) (P < 0.0048), ALP (P < 0.0001) and lactate dehydrogenase (LDH) (P < 0.0192) activities. Plasma Zn was not affected by phytase supplementation. These results demonstrated that microbial phytase supplementation to low-P diets improved performance; P, Ca, Mg, and Zn use; and tibia weight and relative liver weight in broiler chickens. Likewise, serum AST, ALT, ALP, and LDH activities, as well as TP concentration, were also affected by phytase supplementation.

Influence of dietary phytase supplementation on incidence and severity in broilers divergently selected for tibial dyschondroplasia

A study was conducted to determine the effect of dietary supplementation of phytase on the incidence and severity of tibial dyschondroplasia (TD) in chickens selected for high (HTD) and low (LTD) incidences of TD for 11 generations. By feeding a phosphorus-deficient diet (0.1% nonphytate phosphorous; nPP), HTD and LTD chickens were further identified as high-sensitivity birds (HS) and low-sensitivity birds (LS) to phosphorus deficiency based on mortality. Two hundred forty 1-d-old chicks from HTD and LTD lines (five replications of four birds per treatment) were randomly assigned to a control diet with 0.5% nPP and two treatment diets (0.1% nPP) with and without 600 phytase units (FTU) Natuphos phytase/kg. Feed consumption and growth rate were measured for 3 wk, and both tibiae were scored for TD incidence, average TD score, and total number of TD lesions with the most severe form of the abnormality (lesions that were scored 3). The addition of phytase had no influence on TD incidence and lesion scores of 3 in HTD chicks. However, a nonsignificant reduction in TD incidence (P = 0.07), TD score, and no. 3 lesions (P < or = 0.01) were observed in LTD chicks. Interactions between sensitivity (to P deficiency) and phytase (P < or = 0.01) and sensitivity and nPP (P < or = 0.01) were observed for no. 3 scores in LTD chicks. These results indicate that phytase was effective in reducing TD incidence and severity in LTD chicks but not in HTD chicks.