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PubMed1993

Phosphorus studies in pigs. 1. Available phosphorus requirements of grower/finisher pigs.

Two experiments were conducted to determine the available P requirements of grower and grower/finisher pigs and to define the conditions for conducting a growth assay for P availability. In the first experiment, diets with four levels of calculated available P (1-4 g/kg) and four Ca:available P ratios (1.7-2.9) were used to determine the available P requirements of grower pigs. The diets were formulated by substituting the required amounts of limestone and sodium tripolyphosphate for sugar in a soya-bean meal and sugar-based diet. In addition to measuring growth responses, a range of bones were examined to determine the most suitable criteria for assessing the response to available P. There was a small quadratic response of feed intake and growth rate of the pigs to level of available P, with maximum responses occurring to approximately 3 g available P/kg (P < 0.05). There were linear depressing effects of increasing Ca:available P ratios on carcass gain and feed conversion ratio (P < 0.01) but most of these effects occurred when the ratio exceeded 2.5:1. All bone variables examined increased linearly (P < 0.05) or curvilinearly (P < 0.01) with increasing available P concentration. In general, these variables were not affected by the Ca:available P ratio. The results of the growth responses and bone development indicate that the grower pig requires approximately 3 g available P/kg. However, for availability assays, where linearity of response is needed, the dietary concentration of available P should be a maximum of approximately 2 g/kg. In the second experiment four levels of calculated available P (1-4 g/kg) with a Ca:available P ratio of 2.5:1 were used to determine the available P requirements of grower/finisher pigs from 20 to 90 kg live weight. At 50 kg live weight the dietary available P concentration for half the pigs fed at 2, 3 and 4 g available P/kg was reduced to 1, 2 and 3 g/kg respectively. The pigs were fed ad lib, and growth performance, bone characteristics, P retention and ash concentration in the empty body were taken as response criteria to assess P adequacy. Among the variables tested, the ash concentration in the radius/ulna bone and P and ash concentrations in the empty body appeared to be more responsive than other variables to the changes in dietary P levels.(ABSTRACT TRUNCATED AT 400 WORDS)

Animal Nutritional Physiological Phenomena↗
PubMed1993

Phosphorus studies in pigs. 2. Assessing phosphorus availability for pigs and rats.

Experiments were conducted with pigs and rats to determine the availability of P in feeds. Initially, the availability of P in a soya-bean meal and field peas (Pisum sativum cultivar Early Dun) was assessed using a slope-ratio assay for grower pigs. Three different levels of either monosodium phosphate (MSP), soya-bean meal or field peas were added to a basal sucrose-soya-bean meal diet (2.5 g/kg P) to give three levels of P (3.0, 3.5 and 4 g/kg) for each source. The diets were offered for 35 d at three times maintenance energy requirements to female pigs initially weighing 20 kg live weight. Several bone variables and the ash and P concentration and retention levels in the empty body were used as criteria of availability. The responses to MSP were linear for all variables. However, responses to P in the test proteins, particularly soya-bean meal, were mostly non-linear, except for ash and P concentrations and retentions in the empty body. The estimates of P availability in the soya-bean meal and in the field peas were dependent on the criteria used to assess availability. Using bone variables as the criterion, the availabilities of P in soya-bean meal and field peas were approximately 0.17 and 0.38 respectively. Using ash or P concentrations or retentions in the empty body as the response criterion, the availabilities of P in soya-bean meal and field peas were 0.61 and 0.38 respectively. The mean retention values for P from MSP, soya-bean meal and field peas were 0.74, 0.33 and 0.21 respectively. Experiments were then conducted to define the conditions necessary for a slope-ratio assay for P availability with growing rats to determine if they could be used as a model to assess P availability for pigs. These experiments examined level of P in the diet, the effect of Ca:P ratio and criteria for assessing response (growth rate, feed intake, feed conversion ratio, bone ash and bone bending moment). The results indicated that a suitable range of dietary P for a slope-ratio assay in rats was 1.8-3.5 g/kg, with Ca:P ratio of between 1.3 and 6.2, and that ash content or bone bending moment of the femur bone were suitable criteria of response. However, using bone bending moment as the criterion of response, the availability of P in soya-bean meal was 0.81, which was considerably higher than the estimate with pigs.(ABSTRACT TRUNCATED AT 400 WORDS)

Animal Feed↗
PubMed1993

Phosphorus studies in pigs. 3. Effect of phytase supplementation on the digestibility and availability of phosphorus in soya-bean meal for grower pigs.

Two experiments were conducted (1) to determine the effects of phytase (EC 3.1.3.26) on the digestibility and availability of P in soya-bean meal for growing pigs and (2) to compare growth v. digestibility variables for assessing the availability of P. In the first experiment the effect of phytase on P availability was assessed in a growth assay using a slope-ratio design of treatments. Two different levels of either monosodium phosphate (MSP) or soya-bean meal were added to a basal sugar-soya-bean-meal diet (2.5 g P/kg) to give two levels of P (g/kg): 3.25 and 4.0 for each source. An additional five diets were supplemented with phytase. The ten diets were offered ad lib. for 35 d to female pigs initially weighing 20 kg live weight. In addition, the relative effectiveness of different variables for assessing P availability were compared: bone bending moment, ash in various bones, and ash and P in the empty body. The addition of phytase increased growth rate (g/d) (741 v. 835; P < 0.05), lowered the food conversion ratio (2.37 v. 2.16; P < 0.01), and increased protein deposition (g/d) (108 v. 123; P < 0.05), protein retention (kg/kg) (0.33 v. 0.36; P < 0.05), energy retention (MJ gross energy/MJ digestible energy) (0.36 v. 0.38; P < 0.05) and the availability of P in soya-bean meal from 0.11 to 0.69 when bone bending moment was the criterion of availability. All other criteria for assessing availability were unsuitable. In the second experiment the availability of (P) in soya-bean meal was assessed in a digestibility experiment with grower pigs using diets 1-5 as for Expt 1 arranged in a slope-ratio design of treatments. In addition, the effects of phytase supplementation on the apparent digestibility of P, dry matter, crude protein (N x 6.25) and energy were determined. The diets were offered at three times maintenance energy requirements to male pigs initially weighing approximately 30 kg live weight and total collection of faeces was conducted over a 10 d period. The availability of P in the soya-bean meal was 0.66 using digestible P intake as the criterion of response. The apparent digestibility of P in soya-bean meal was 0.42. Phytase supplementation increased the apparent digestibility of soya-bean meal P to 0.69 (P < 0.01) but had no effect on the faecal digestibility of dry matter or crude protein.(ABSTRACT TRUNCATED AT 400 WORDS)

6-Phytase↗
PubMed1995

Absorption and endogenous excretion of phosphorus in growing broiler chicks, as influenced by calcium and phosphorus ratios in feed.

Absorption and endogenous excretion of P by male broiler chicks (14-29 d old) were quantitatively evaluated at different Ca:P ratios (1, 1:1; 2, 1.5:1; 3, 2:1; 4, 2.5:1) in four groups given experimental diets ad lib. The P content was the same in all diets. An isotope-dilution technique was used to determine endogenous faecal and renal excretion. Ca and P retentions in the whole body were estimated according to the comparative slaughter technique. P absorption was calculated from retention and endogenous excretion. Absorption and endogenous excretion of P amounted to (mg P/d per chick): 304, 270, 160 and 158; and 135, 109, 31 and 30 in groups 1, 2, 3 and 4 respectively. Widening of the Ca:P ratio in the feed limited the P absorption. Availability of feed P amounted to (%): (1) 66, (2) 57, (3) 32 and (4) 30, and the amounts of absorbed P retained were (%): (1) 56, (2) 60, (3 and 4) 81. The increasing Ca concentration in the feed showed a greater effect on P absorption than on P retention. The ratios of relative retention to relative endogenous excretion of absorbed P were: (1) 1.27, (2) 1.50, (3 and 4) 4.26.

Animals↗
PubMed1996

Effects of supplemental phytase and phosphorus on histological, mechanical and chemical traits of tibia and performance of turkeys fed on soyabean-meal-based semi-purified diets high in phytate phosphorus.

Tibial traits were investigated for turkey poults fed on soyabean-meal-based semi-purified diets high in phytate P (2.2 g/kg) with added phytase and inorganic P. Dietary treatments were: (1) 2.7 g non-phytate P (nP)/kg; (2) diet 1 + 1000 U phytase/kg diet; (3) 3.6 g nP/kg; (4) diet 3 + 800 U phytase; (5) 4.5 g nP/kg; (6) diet 5 + 600 U phytase; (7) 6.0 g nP/kg. Added phytase and nP increased (P < 0.006) tibial dry matter, ash weight and content, body-weight gain, feed intake and gain:feed. The Mg and Zn concentrations in the tibial ash were also increased (P < 0.001 and P < 0.09 respectively) by added phytase or nP; tibial P and Ca concentrations tended to be increased. Hypertrophy zone width of the tibial proximal end decreased (P < 0.001), while proliferating zone width, tibial length, and widths at the long and short axes increased (P < 0.003) as phytase and nP were added. The addition of phytase also tended to enlarge the cartilaginous zone width, which was linearly increased (P < 0.05) by added nP. Disorganization scores of the hypertrophy zone and trabecular bone were low, approaching normal (P < 0.05), for turkey poults fed on diets with phytase supplementation, and tibial abnormality scores were linearly decreased (P < 0.001) as nP levels increased (zero score is considered normal). Adding phytase and nP improved the orderliness of development, mineralization and arrangement of cartilage and bone cells, and alleviated the effects of P deficiency on the histological and gross structure of the tibias. Tibial shear stress increased (P < 0.04) as phytase and nP were added. In summary, similar improvements in bone characteristics were achieved for turkey poults fed on a P-deficient diet supplemented with either phytase or nP.

6-Phytase↗
PubMed2004

The ability of laying hens to regulate phosphorus intake when offered two feeds containing different levels of phosphorus.

The ability of laying hens to adjust their intake of available P (AP) was investigated with a maize-soyabean diet fed to forty-eight individually caged birds in a 2 x 4 factorial experiment. From 19 to 25 weeks of age (phase 1) twenty-four birds were fed a normal-P (NP) diet (2.2 g AP/kg DM) and twenty-four were fed a low-P (LP) diet (1.1 g AP/kg). LP eggs were lighter (51 v. 54 (SEM 1.0) g; P<0.05), providing evidence that the LP diet was deficient in AP. From 25 to 28 weeks of age six hens from each phase 1 treatment were fed either the NP or LP diet alone or a choice of the LP and NP feeds or a choice of the LP feed and a phytase-supplemented (PP) feed (LP diet with 400 microbial phytase units/kg). With a choice of the NP and LP feeds, the hens fed the LP diet in phase 1 ate a smaller proportion of the LP feed (34 (SEM 12.0) %) than the hens fed the NP diet in phase 1 (72 (SEM 12.0) %; P<0.05), showing that P deficiency influenced subsequent selection for AP, i.e. an appetite for P was demonstrated. In those birds offered the LP and PP feeds, the presence of phytase in one of the two feeds significantly alleviated the effect of P deficiency on egg and body weights. The proportion of the LP diet chosen was not significantly affected by phase 1 treatment; it was not necessary for the hens to eat more than 50 % of PP feed.

6-Phytase↗
PubMed2002

Release potential of phosphorus in Florida sandy soils in relation to phosphorus fractions and adsorption capacity.

Information on P release potential in relation to labile P and P fractions in sandy soils is limited. In this study, P release potential was determined by leaching, and labile P, soil P fractionation, and P adsorption capacity were measured in the laboratory using 96 Florida sandy soil samples to evaluate the relationship between P release in water and soil P status. The sandy soils had a very low P adsorption capacity. The adsorption maximum, as calculated from the Langmuir equation, averaged 40.4 mg P kg(-1). More than 10% of the soil P was water soluble, indicating a high risk of P leaching from soil to water. Successive leaching using deionized water released, on average, 7.7% of total P (144.5 mg kg(-1)) in different soils, whereas labile P recovered by successive water extraction accounted for 39.2% of the total P. Variation in release potential among the different soils could be explained more by the difference in amounts of extractable P than the adsorption capacity. Total amounts of P released by successive leaching were significantly correlated with all labile P indices measured by different methods and all soil P fractions except for residual P. The correlation coefficients (r) were 0.97** for water-soluble P, 0.96** for 0.01 M CaCl2-P, 0.94** for Olsen P, 0.86** for Mehlich 1-P, 0.77*** for Mehlich 3-P, and 0.64*** for Bray 1-P. There were no obvious turning points in the relationships between Olsen-P, water-soluble P, or CaCl2-P and the amounts of P released from the sandy soils. The release of P from the sandy soils appeared to be controlled by a precipitation-dissolution reaction rather than a P sorption-desorption process. Furthermore, the sequential extraction of soils using deionized water indicated that P released was not limited to the labile P (H2O-P, NaHCO3-IP) and potentially labile P (NaOH-P) pools, but also from the HCl-P, indicating that all of P fractions except for residual P in the sandy soils can contribute to P release.

Adsorption↗
PubMed2000

Nonphytate phosphorus requirement and phosphorus excretion of broiler chicks fed diets composed of normal or high available phosphate corn with and without microbial phytase.

A study was conducted to evaluate the ability of the young (0 to 3 wk) broiler chicken to utilize the P provided by a high available P corn [HAPC; 0.27% total P and 0.17% nonphytate P] in comparison with yellow dent corn (YDC; 0.23% total P and 0.03% nonphytate P), and to determine the extent to which supplementation with exogenous phytase enzyme could reduce the demands for dietary P and subsequently reduce P excretion. Diets prepared using the two types of corn differed in the amount of phytate-bound P, with the HAPC diets containing approximately 50% less phytate-bound P. Treatment diets were prepared by varying the amount of dicalcium phosphate, and ranged from 0.10 to 0.50% nonphytate P for YDC diets, and from 0.18 to 0.50% nonphytate P for HAPC diets. Sublots of each diet were supplemented with 800 units/kg phytase. Each diet was fed to six pens of five male chicks of a commercial broiler strain from 1 to 21 d of age. Regression analysis was used to estimate nonphytate P requirements for each corn type with and without phytase supplementation. The greatest need for nonphytate P was for maximum tibia ash, with requirements of 0.39, 0.29, 0.37, and 0.32% in diets with YDC, YDC plus phytase, HAPC, and HAPC plus phytase, respectively. Addition of phytase liberated approximately 50% of the phytate-bound P from each diet. These levels were sufficient to support body weight, feed conversion, and livability. Fecal P content of broilers fed diets with YDC at the NRC (1994) recommended level of 0.45% nonphytate P was 1.21%, whereas at the respective requirement points indicated above, the P content was 1.09, 0.87, 0.78, and 0.64% in feces from broilers fed diets with YDC, YDC plus phytase, HAPC, and HAPC plus phytase, respectively. Thus, fecal P output could be reduced while maintaining optimum performance by the use of reduced dietary nonphytate P, introduction of HAPC, and phytase supplementation. One of the greatest benefits of phytase supplementation appeared to be maintaining livability at lower dietary levels of nonphytate P.

6-Phytase↗
PubMed2003

Total and water-soluble phosphorus in broiler litter over three flocks with alum litter treatment and dietary inclusion of high available phosphorus corn and phytase supplementation.

Three pen trials were conducted to determine the main effect of alum addition to litter on form of poultry litter P using a 2 x 2 factorial structure of the subunit treatments: diets including high available phosphorus/low phytate corn (HAPC) and phytase (PHYT). Male broilers (1,760 per flock) were grown to 42 d having starter diets with 0.45% available P and grower diets with 0.35% available P. In the first trial, total litter P (tP) was greatest for the yellow dent corn (YDC) diet (12 g/kg) and least for the HAPC and PHYT combination (H&P) diet (6.9 g/kg) with the individual PHYT and HAPC diets falling in between at 9.1 g/kg and 9.4 g/kg tP. Also in the first trial, the litter water-soluble P (wP) was highest for PHYT (2.8 g/kg), least for the HAPC and H&P diets (1.5 g/kg) with the YDC diet falling between (2.2 g/kg). Alum was added to the litter after the first experiment. In the second and third experiments, alum inclusion significantly reduced the wP when compared with the treatments with no alum. In the third trial, the least wP was present in the alum-HAPC treatment. Phytase, YDC, and HAPC diets with no alum litter treatment generated the most wP. Since these diets appear to have little or no difference with respect to quantity of wP, this work suggests that form of litter P generated by alternative diets should be considered as criteria when attempting to reduce P in broiler litter applied to land.

6-Phytase↗
PubMed2006

Estimation of true phosphorus digestibility and endogenous phosphorus loss in growing chicks fed conventional and low-phytate soybean meals.

This study evaluated regression of total P output against dietary P intake to simultaneously estimate endogenous P loss and true P utilization in broiler chicks. Soybean meal (SBM) served as the model ingredient, and a comparison was made between conventional and low-phytate SBM varieties. These feedstuffs were chosen to minimize nutritive differences to dietary phytate content. Low-phytate SBM contained 57% less phytate than conventional SBM. Four isocaloric diets were formulated to contain graded levels of each soybean meal (8 diets total); therefore, the diets also contained graded levels of dietary P. Chromium sesquioxide was included in diets as an indigestible marker, and free access to experimental diets was provided to 288 male broiler chicks from 15 to 22 d posthatch. The experiment was arranged as a randomized complete block design with 6 blocks of 8 cages (6 birds per cage) and similar initial BW across dietary treatments. As P intake ranged from 0.9 to 3.9 g/ kg of DM, apparent prececal P digestibilities increased (linear and quadratic, P < 0.01) for conventional SBM and low-phytate SBM. Increasing linear relationships (P < 0.01) were observed for total P output (mg/kg of DM intake) with graded P intake, regardless of SBM variety. True P retention was greater (P < 0.01) for low-phytate SBM (76.9%) than for conventional SBM (59.8%). Endogenous P estimates were not different between soybean meals (P > 0.10), and an overall estimate of 235 mg of P/ kg of DM intake was observed. This study concluded 1) the regression approach may be applicable in the estimation of endogenous P loss in broiler chicks and 2) the difference in P utilization between conventional and low-phytate soybean meals is influenced by dietary phytate content when broiler chicks are fed P-deficient diets.

Animal Feed↗
PubMed2006

Effect of dietary phosphorus, phytase, and 25-hydroxycholecalciferol on broiler chicken bone mineralization, litter phosphorus, and processing yields.

Three floor pen experiments (Exp) were conducted to evaluate low nonphytin P (NPP) concentrations and the NPP sparing effect of phytase (PHY) and 25-hydroxycholecalciferol (25D) on bone mineralization, bone breaking during commercial processing, litter P, and water-soluble P (WSP) concentrations. Tested treatments (TRT) were control, National Research Council NPP; University of Maryland (UMD) NPP; UMD + PHY, UMD NPP reduced by 0.064% NPP + 600 U of PHY/kg; UMD + PHY + 25D, UMD NPP reduced by 0.090% NPP + 600 U of PHY and 70 microg of 25D/kg; control + PHY mimicked the industry practice of diets by 0.1% when PHY is added; and negative control with 90% UMD NPP concentrations. UMD + PHY and control + PHY diets contained 600 U of PHY/kg, and UMD + PHY + 25D contained 600 U of PHY + 70 microg of 25D/kg. Performance results were presented separately. After each Exp, litter P and WSP were determined, and bone measurements were obtained on 8 or 10 broilers per pen. Tested TRT did not affect broiler BW. Femur ash weight of broilers fed the UMD and UMD + PHY + 25D was lower in all Exp compared with that of broilers fed the control diet. Femur ash was similar for control and UMD + PHY broilers, yet averaged over all Exp, UMD + PHY broilers consumed 39% less NPP and required less NPP per gram of femur ash than those on the control (4.87 and 7.77 g of NPP/g of ash, Exp 3). At the end of Exp 3, broilers were processed in a commercial facility. Despite reductions in NPP intake and bone mineralization, no differences were observed in measurements of economic importance (parts lost, carcass yield, and incidence of broken bones). The P excretion per bird was lowest for birds fed the UMD + PHY + 25D diet followed by those fed the UMD + PHY and negative control diets (10.44, 12.00, and 13.78 g of P/bird, respectively) and were highest for those fed the control diet (19.55 g of P/bird). These results suggest that feeding diets low in P together with PHY and 25D will not affect performance or increase losses at processing while resulting in improved P retention and reductions in P and WSP excreted.

6-Phytase↗