Standardized Total Tract Digestibility Of Phosphorus Research Articles

Impact of dietary analyzed calcium to phosphorus ratios and standardized total tract digestible phosphorus to net energy ratios on growth performance, bone, and carcass characteristics of pigs.

A total of 2,184 pigs (337 × 1,050, PIC; initially 12.4 ± 0.17 kg) were used in a 143-d study to evaluate the effects of feeding varying analyzed calcium to phosphorus ratios (Ca:P) at two standardized total tract digestible (STTD) phosphorus to net energy ratios (STTD P:NE). Pens of pigs (26 pigs per pen) were assigned to 1 of the 6 dietary treatments in a 2 × 3 factorial with main effects of STTD P:NE and Ca:P ratio. Diets consisted of two levels of STTD P:NE; High (1.80, 1.62, 1.43, 1.25, 1.10, and 0.99 g STTD P/Mcal NE from 11 to 22, 22 to 40, 40 to 58, 58 to 81, 81 to 104, and 104 to 129 kg, respectively); or Low (75% of the High levels), and three analyzed Ca:P ratios (0.90:1, 1.30:1, and 1.75:1). There were 14 pens per treatment. Diets were corn-soybean meal-based and contained a constant phytase concentration within each dietary phase with levels decreasing throughout the trial (phases 1 through 3, 500 FTU/kg, assumed release of 0.13% STTD P; phase 4, 400 FTU/kg, assumed release of 0.11% STTD P; phase 5, 290 FTU/kg, assumed release of 0.09% STTD P; and phase 6, 210 FTU/kg, assumed release of 0.07% STTD P). Overall, there was a Ca:P × STTD P:NE interaction (P < 0.05) observed for average daily gain (ADG), feed efficiency (G:F), final body weight (BW), hot carcass weight (HCW), bone mineral density, bone mineral content, and bone-breaking strength. When feeding Low STTD P:NE levels, increasing the analyzed Ca:P ratio decreased (linear, P < 0.001) ADG final BW, HCW, and tended to worsen G:F, bone mineral density, and bone mineral content (linear, P < 0.10). However, when feeding High STTD P:NE levels, increasing the analyzed Ca:P ratio significantly improved bone mineral content and bone mineral density (linear, P < 0.05), and tended to improve ADG and final BW (linear, P < 0.10) and G:F (quadratic P < 0.10). Additionally, increasing the analyzed Ca:P ratio worsened ADG, G:F, and bone mineralization with Low STTD P:NE but had marginal impacts when adequate STTD P:NE was fed.

Additivity of digestible energy and nutrient concentrations in hatchery byproducts fed to nursery pigs.

ObjectiveThe objective was to test additivity of digestible energy and nutrient concentrations in the hatchery byproduct mixture fed to nursery pigs.MethodsIn the previous studies, energy, phosphorus, calcium, and amino acid digestibility of infertile eggs, unhatched eggs, culled chicks, and a mixture of 3 hatchery byproduct ingredients was determined in nursery pigs (initial body weight = 9.4 to 14.2 kg). An additivity test was conducted using these determined values.ResultsNo difference was observed between determined and predicted metabolizable energy values in the mixture (3,998 and 3,990 kcal/kg as-is basis, respectively). Measured standardized total tract digestible phosphorus in the mixture was less than the predicted value (4.5 vs 5.3 g/kg as-is basis, respectively; p<0.05). Measured standardized total tract digestible calcium in the mixture was greater compared with the predicted value (40.0 vs 31.7 g/kg as-is basis, respectively; p<0.05). Measured standardized ileal digestible tryptophan in the mixture was greater than the predicted value (3.7 vs 3.1 g/kg as-is basis, respectively; p<0.05) whereas other amino acid values were additive.ConclusionEnergy and most of amino acid concentrations in hatchery byproducts are additive in the mixture fed to nursery pigs.

Effect of high-phytase supplementation in lactation diets on sow and litter performance.

A total of 109 sows (Line 241; DNA, Columbus, NE) were used to evaluate the effect of increasing dietary phytase in lactation diets, already adequate in P, on sow and litter performance. On d 107 of gestation, sows were blocked by body weight and parity and allotted to 1 of 3 dietary treatments of increasing phytase concentration (0, 1,000, or 3,000 FYT/kg; Ronozyme HiPhos GT 2700, DSM Nutritional Products, Inc., Parsippany, NJ). The control diet contained no phytase and was formulated to contain 0.50% standardized total tract digestible phosphorus (STTD P; 0.45% available P) and 0.62% STTD calcium (0.90% total Ca). The phytase diets that contained 1,000 or 3,000 FYT/kg were also formulated to 0.50% STTD P and 0.62% STTD Ca including the release of 0.132% STTD P and 0.096% STTD Ca. Diets were balanced for net energy and fed from d 107 of gestation until weaning (d 18 ± 3). All farrowings were monitored, with farrowing duration starting at the time the first pig was born until the first dispersal of placental tissues with no subsequent pigs born. Litters were cross-fostered within treatment until 48 h postfarrowing to equalize litter size. There were no differences among treatments in sow body weight at d 107 of gestation, 24 h after farrowing, or at weaning. Sow average daily feed intake from farrowing to weaning tended to increase (linear, P = 0.093) as phytase increased. There was no evidence for difference in the number of total born pigs, as well as the percentage of stillborns, mummies, and born alive pigs at the completion of farrowing. Similarly, phytase supplementation did not influence (P > 0.05) wean-to-estrus interval or litter size after cross-fostering among dietary treatments. Although not significant (linear, P = 0.226), farrowing duration decreased as added phytase increased with a decrease of 47 min (12%) for 3,000 FYT compared with the control. There were no differences in pig weight at weaning, but as a result of increased survivability (linear, P = 0.002), litter weaning weight and overall litter weight gain increased (quadratic, P < 0.05) up to 1,000 FYT of added phytase with no further benefit observed in sows fed 3,000 FYT. In conclusion, sow feed intake tended to increase linearly with increasing added phytase. Feeding 1,000 FYT/kg maximized overall litter gain and weaning weight; however, a larger-scale study with more sows is needed to determine the addition of phytase in lactation diets to reduce farrowing duration.

269 Effects of high phytase supplementation in lactation diets on sow and litter performance

Abstract A total of 109 sows (Line 241; DNA, Columbus, NE) were used in a study to evaluate the effect of increasing phytase concentration in lactation diets on sow and litter performance. On d 107 of gestation, sows were blocked by body weight and parity and allotted to 1 of 3 dietary treatments of increasing phytase concentration (0, 1,000, or 3,000 FYT/kg; Ronozyme HiPhos 2700; DSM Nutritional Products, Inc., Parsippany, NJ). The control diet contained no phytase and was formulated to contain 0.50% standardized total tract digestible phosphorus (STTD P; 0.45% available P) and 0.62% STTD calcium (0.90% total Ca). The same STTD P and Ca concentrations were formulated for the phytase diets considering a release of 0.132 STTD P and 0.094 STTD Ca in both diets. Diets were fed from d 107 of gestation until weaning (d 18 ± 2). Litters were cross-fostered within treatment until 48 h post-farrowing to equalize litter size. Linear and quadratic response to phytase concentration was evaluated using the lmer function in R. There was no evidence for difference in sow body weight change, farrowing performance, wean-to-estrus interval, or litter size among dietary treatments. Sow average daily feed intake from farrowing to weaning tended to increase (linear, P=0.093) as phytase increased. Although not significant (linear, P =0.226), farrowing duration decreased as phytase increased. Litter weaning weight increased (quadratic, P=0.039) and overall litter gain increased (quadratic, P=0.047) with 1,000 FYT of phytase. In summary, sow feed intake tended to increase linearly with increasing phytase; however, feeding 1,000 FYT/kg maximized overall litter gain and weaning weight. This small-scale study suggests sow and litter performance benefits due to high inclusions of dietary phytase; however, a commercial trial with more sows is warranted to confirm these results.

Evaluation of a decision support system for precision feeding of gestating sows.

Precision feeding (PF) with the daily mixing of 2 diets with different lysine content (high (H) or low (L)) was previously reported for growing pigs to reduce protein intake and N excretion compared with a conventional feeding (CF) based on a single diet (C). Using a simulation approach based on farm data, the objective of the present paper was to describe and evaluate a decision support system for the PF of gestating sows allowing the daily distribution of a tailored ration to each sow. Two datasets, 1 of 2,511 gestations (farm A) and 1 of 2,528 gestations (farm B), reporting sows’ characteristics at insemination and objectives at farrowing were used as inputs for a Python model. This model, mainly based on InraPorc, calculates the nutrient requirements of each sow over gestation and simulates the impact of PF in comparison to CF. Simulated diets L, H, and C contained 3.0, 6.5, and 4.8 g/kg of standardized ileal digestible lysine (SID Lys) and 2.0, 3.3, and 2.5 g/kg of standardized total tract digestible phosphorus (STTD-P), respectively. The influence of farm, parity, gestation week, and their interactions, on calculated SID Lys and STTD-P requirements was analyzed applying a mixed model. The calculated SID Lys and STTD-P requirements increased markedly in the last third of gestation (P < 0.01) and were higher for primiparous than for multiparous sows, unless after week 14 for STTD-P requirement. The calculated SID AA and mineral requirements were lower for farm B than farm A (respectively, 2.94 vs. 3.08 g/kg for SID Lys and 1.30 vs. 1.35 g/kg for STTD-P, P < 0.01). On average, feed L represented 86% and 92% of the feed projected to be delivered by the PF strategy in farms A and B, respectively. Compared to CF, average calculated dietary SID Lys content was lowered by 27% and 32% with PF, for farms A and B, respectively, while average calculated dietary phosphorus content was lowered by 13% and 16%. The simulated proportions of sows in excess and deficient in SID Lys were reduced with PF. Compared to CF, the PF strategy allowed for a 3.6% reduction in simulated feed cost per sow during gestation, and reduced nitrogen and phosphorus intake (by 11.0% and 13.8%, respectively) and excretion (by 16.7% and 15.4%, respectively). To conclude, these simulations indicate that PF of gestating sow appears to be relevant to meet the amino acid requirement while reducing feed cost, and supplies and excretion of nitrogen and phosphorus.

Exploration of individual variability to better predict the nutrient requirements of gestating sows1.

Sows often receive the same feed during gestation even though their nutrient requirements vary during gestation and among sows. The objective of this study was to report the variability in nutrient requirement among sows and during gestation, in order to develop a precision feeding approach. A data set of 2,511 gestations reporting sow characteristics at insemination and their farrowing performance was used as an input for a Python model, adapted from InraPorc, predicting nutrient requirement during gestation. Total metabolizable energy (ME) requirement increased with increasing litter size, gestation weeks, and parity (30.6, 33.6, and 35.5 MJ/d for parity 1, 2, and 3 and beyond, respectively, P < 0.01). Standardized ileal digestible lysine (SID Lys) requirement per kg of diet increased from weeks 1 to 6 of gestation, remained stable from weeks 7 to 10, and increased again from week 11 until the end of gestation (P < 0.01). Average Lys requirement increased with increasing litter size (SID Lys: 3.00, 3.27, 3.50 g/kg for small, medium and large litters, P < 0.01) and decreased when parity increased (SID Lys: 3.61, 3.17, 2.84 g/kg for parity 1, 2, and 3++, P < 0.01). Standardized total tract digestible phosphorus (STTD-P) and total calcium (Total-Ca) requirements markedly increased after week 9, with litter size, and decreased when parity increased (STTD-P: 1.36 vs. 1.31 g/kg for parity 1 and parity 3 and beyond; Total-Ca: 4.28 vs. 4.10 g/kg for parity 1 and parity 3 and beyond, P < 0.01). Based on empirical cumulative distribution functions, a 4-diets strategy, varying in SID Lys and STTD-P content according to parity and gestation period (P1 from weeks 0 to 11, P2 from weeks 12 to 17), may be put forward to meet the requirements of 90% of the sows (2 diets for multiparous sows: P1: 2.8 g SID Lys/kg and 1.1 g STTD-P/kg; P2: 4.5 g SID Lys/kg and 2.3 g STTD-P/kg; and 2 diets for primiparous sows: P1: 3.4 g SID Lys/kg and 1.1g STTD-P/kg; P2: 5.0 g SID Lys/kg, 2.2 g STTD-P/kg). Better considering the high variability of sow requirement should thus make it possible to optimize their performance whilst reducing feeding cost and excretion. Feeding sows closer to their requirement may initially be achieved by grouping and feeding sows according to gestation week and parity, and ultimately by feeding sows individually using a smart feeder allowing the mixing of different feeds differing in their nutrient content.

Standardized total tract digestible phosphorus requirement of 24- to 130-kg pigs1,2.

A study was conducted to determine the standardized total tract digestible phosphorus (STTD P) requirement for 24- to 130-kg finishing pigs housed under commercial conditions. A total of 1,130 barrows and gilts (PIC 359 × 1050, Hendersonville, TN; initially 24.2 kg) were used, with 26 to 27 pigs per pen with 7 replicates per treatment. Pens of pigs were allotted to treatments in a randomized complete block design with body weight (BW) as the blocking factor. The dietary treatments were fed in 4 phases and were formulated to contain 80%, 90%, 100%, 115%, 130%, and 150% of the National Research Council (NRC) requirement estimate for finishing pigs within each phase. Weight ranges for each phase were: 27 to 49, 49 to 76, 76 to 90, and 90 to 130 kg. Treatments were achieved by increasing the amount of monocalcium phosphate at the expense of corn in the diet with no added phytase. All diets were formulated to contain a similar 1.14:1 to 1.16:1 total Ca:P ratio across treatments in all phases. Increasing STTD P resulted in a quadratic response (P < 0.05) in average daily gain (ADG), gain-to-feed ratio (G:F), and final BW. The greatest improvement was observed with STTD P at 130% of NRC for ADG and final BW and at 115% STTD P for G:F. Average daily feed intake increased linearly (linear, P < 0.05) with the inclusion of STTD P. Increasing STTD P resulted in an increase (quadratic, P < 0.05) in hot carcass weight (HCW) and carcass ADG with the greatest response observed with STTD P at 130% of NRC. There was a marginally significant response (quadratic, P < 0.10) in carcass G:F, with the greatest improvement with STTD P at 115% of NRC. Carcass yield decreased (linear, P < 0.05) with increasing STTD P, while there was a marginally significant (linear, P < 0.10) decrease in backfat and increase in fat-free lean. At the end of the study, a metacarpal was collected and analyzed for bone ash. Increasing STTD P resulted in an increase (linear, P < 0.05) in bone ash weight and percentage ash. For ADG and G:F, the quadratic model demonstrated the best fit. The maximum response in ADG and G:F was estimated at 122% and 116% of NRC STTD P, respectively. The broken-line linear model best fit the data for percentage bone ash, with a plateau achieved at 131% of the NRC STTD P. In conclusion, the estimated STTD P requirement of 24 to 130 kg ranged from 116% to 131% of the NRC publication (2012) requirement estimate.

Effects of standardized total tract digestible phosphorus on growth performance of 11- to 23-kg pigs fed diets with or without phytase1,2.

Two experiments were conducted to determine the standardized total tract digestible phosphorus (STTD P) requirement for 11- to 23-kg nursery pigs fed diets with or without phytase. A total of 1,080 and 2,140 pigs (PIC 359 × Camborough, Hendersonville, TN; initially 11.4 ± 0.29 and 11.1 ± 0.24 kg) were used in Exp. 1 and Exp. 2, respectively. There were 23 to 27 pigs per pen with 6 and 12 replicate pens per treatment in Exp. 1 and Exp. 2, respectively. After weaning, pigs were fed a common pelleted diet with 0.45% STTD P for 7 d, and a common phase 2 meal diet with 0.40% STTD P for 14 d in Exp. 1 and 18 d in Exp. 2. Pens of pigs were then allotted to dietary treatments in a randomized complete block design with body weight (BW) as the blocking factor. In Exp. 1, dietary treatments consisted of 0.26%, 0.30%, 0.33%, 0.38%, 0.43%, 0.48%, and 0.53% STTD P. Treatments were achieved with the inclusion of monocalcium phosphate at the expense of corn. In Exp. 2, diets contained 1,000 phytase units (FYT; Ronozyme Hiphos 2500, DSM Nutritional Products, Inc., Parsippany, NJ) with assumed release value 0.132% STTD P, and treatments consisted of 0.30%, 0.33%, 0.38%, 0.43%, 0.48%, 0.53%, and 0.58% STTD P. These STTD P concentrations included the expected phytase release of 0.132% STTD P. In both experiments, a similar 1.17:1 Ca:P ratio was maintained across treatments. Statistical models included linear model (LM), quadratic polynomial (QP), broken-line linear (BLL), and broken-line quadratic (BLQ). In Exp. 1, increasing STTD P increased (linear, P < 0.001) ADG, ADFI, G:F, final BW, and grams of STTD P intake per day and per kilogram of gain. There was also a marginal quadratic response for G:F (P < 0.066). In Exp. 2, ADG and G:F increased quadratically (P < 0.05), whereas ADFI increased linearly (P = 0.060) with increasing STTD P. The BLL and QP model provided similar fit to G:F in Exp. 1, estimating the requirement for maximum G:F at 0.34% and 0.42%, respectively. The BLL was the best fitting model for ADG and G:F in Exp. 2, estimating the breakpoint at 0.40% and 0.37% STTD P, respectively. The BLL and BLQ models estimated the breakpoint for ADG as a function of STTD P intake in grams per day at 2.92 and 3.02 g/d, respectively. These data provide empirical evidence that for 11- to 23-kg pigs, the NRC (2012) accurately estimates the STTD P requirement on a g/d basis. As a percentage of the diet, the STTD P requirement for diets without or with 1,000 FYT added phytase ranged from 0.34% to 0.42%.

172 Standardized total tract digestible phosphorus requirement of 11- to 23-kg pigs fed diets containing phytase

Abstract The objective of this study was to determine the standardized total tract digestible phosphorus (STTD P) requirement of nursery pigs from 11 to 23 kg fed diets containing 1,000 phytase units (FYT). A total of 2,140 barrows and gilts (PIC 359×Camborough, initial BW 11.1 ± 0.24 kg) were used in a 21-d growth trial with 24 to 27 pigs per pen and 12 pens per treatment in a randomized complete block design. The 7 dietary treatments consisted of 0.30, 0.33, 0.38, 0.43, 0.48, 0.53, and 0.58% STTD P, which represented 90, 100, 115, 130, 145, 160 and 175%, respectively, of the NRC (2012) requirement estimate for STTD P for pigs weighing 11 to 23 kg. All diets contained 1,000 FYT of Ronozyme Hiphos 2500 (DSM Nutritional Products, Inc., Parsippany, NJ) with assumed release values of 0.15% available P and 0.132% STTD P. Treatments were achieved by increasing the amount of calcium carbonate and monocalcium phosphate at the expense of corn, while maintaining a similar 1.17:1 total Ca:total P ratio across treatments. Experimental data were analyzed with pen as the experimental unit, using generalized linear and nonlinear mixed models, which included quadratic polynomial, broken-line linear, and broken-line quadratic models. Increasing STTD P quadratically improved (P &lt; 0.05) ADG and feed efficiency (G:F). Final BW and ADFI increased linearly (P &lt; 0.05) up to the highest STTD P level. Income over feed cost improved quadratically (P &lt; 0.05), with the highest income observed at 0.43% STTD P. The broken-line linear plateau was estimated at 0.40% STTD P for ADG and at 0.37% STTD P for G:F. In conclusion, the estimated STTD P requirement for nursery pigs from 11 to 23 kg fed diets containing 1,000 FYT were greater than NRC (2012) requirement estimates and ranged from 0.37 to 0.43% to optimize performance and economic return.

Prediction models for apparent and standardized total tract digestible phosphorus in swine diets

The objectives of the present study were to develop equations for predicting apparent total tract digestible (ATTD) phosphorus (P) and standardized total tract digestible (STTD) P based on total P, phytate-P, and supplemental phytase concentrations in swine diets and to evaluate the accuracy of the prediction models using published values. A total of 500 observations from 78 experiments were employed to develop equations for predicting ATTD P and STTD P in swine diets. In the 500 observations, total P ranged from 1.05 to 7.90 g/kg, phytate-P ranged from 0.40 to 6.18 g/kg, and supplemental phytase ranged from 0 to 2.50 phytase unit/g (as-fed basis). The ATTD P was positively correlated with total P (r = 0.71; P < 0.001), phytate-P (r = 0.21; P < 0.001), and phytase concentrations (r = 0.32; P < 0.001). The STTD P was also positively correlated with total P (r = 0.71; P < 0.001), phytate-P (r = 0.21; P < 0.001), and phytase concentrations (r = 0.33; P < 0.001). Linear, quadratic, and exponential models for predicting ATTD P and STTD P were developed. Among the 3 prediction models, the exponential model which had the lowest Akaike information criterion and Bayesian information criterion was regarded the most accurate one for predicting digestible P. The accuracy of the prediction models was tested using 42 recently published STTD P values from diets with varying phytate-P and supplemental phytase concentrations that were not used in developing the prediction models. To test the accuracy of the current models, regression analysis was conducted to determine mean bias and linear bias. Predicted STTD P values were in very good agreements with measured values in all 3 equations based on nonsignificant bias in the models. In conclusion, all models were accurate in the validation test, but the exponential model was the most biologically reasonable.

Effects of High Phytase Supplementation in Lactation Diets on Sow and Litter Performance

A total of 109 sows (Line 241; DNA, Columbus, NE) were used to evaluate the effect of increasing dietary phytase in lactation diets, already adequate in P, on sow and litter performance. On d 107 of gestation, sows were blocked by body weight and parity and allotted to 1 of 3 dietary treatments of increasing phytase concentration (0, 1,000, or 3,000 FYT/kg; Ronozyme HiPhos GT 2700, DSM Nutritional Products, Inc., Parsippany, NJ). The control diet contained no phytase and was formulated to contain 0.50% standardized total tract digestible phosphorus (STTD P; 0.45% available P) and 0.62% STTD calcium (0.90% total Ca). The phytase diets that contained 1,000 or 3,000 FYT/kg were also formulated to 0.50% STTD P and 0.62% STTD Ca including the release of 0.132% STTD P and 0.096% STTD Ca. Diets were balanced for net energy and fed from d 107 of gestation until weaning (d 18 ± 3). All farrowings were monitored, with farrowing duration starting at the time the first pig was born until the first dispersal of placental tissues with no subsequent pigs born. Litters were cross-fostered within treatment until 48 h postfarrowing to equalize litter size. There were no differences among treatments in sow body weight at d 107 of gestation, 24 h after farrowing, or at weaning. Sow average daily feed intake from farrowing to weaning tended to increase (linear, P = 0.093) as phytase increased. There was no evidence for difference in the number of total born pigs, as well as the percentage of stillborns, mummies, and born alive pigs at the completion of farrowing. Similarly, phytase supplementation did not influence (P > 0.05) wean-to-estrus interval or litter size after cross-fostering among dietary treatments. Although not significant (linear, P = 0.226), farrowing duration decreased as added phytase increased with a decrease of 47 min (12%) for 3,000 FYT compared with the control. There were no differences in pig weight at weaning, but as a result of increased survivability (linear, P = 0.002), litter weaning weight and overall litter weight gain increased (quadratic, P < 0.05) up to 1,000 FYT of added phytase with no further benefit observed in sows fed 3,000 FYT. In conclusion, sow feed intake tended to increase linearly with increasing added phytase. Feeding 1,000 FYT/kg maximized overall litter gain and weaning weight; however, a larger-scale study with more sows is needed to determine the addition of phytase in lactation diets to reduce farrowing duration.

117 Prediction models for standardized total tract digestible phosphorus in swine diets

117 Prediction models for standardized total tract digestible phosphorus in swine diets

A cooperative study on the standardized total-tract digestible phosphorus requirement of twenty-kilogram pigs1

A cooperative study comprising growth performance, bone mineralization, and nutrient balance experiments was conducted at 11 stations to determine the standardized total-tract digestible (STTD) P requirement of 20-kg pigs using broken-line regression analysis. Monocalcium phosphate and limestone were added to a corn-soybean meal-based diet at the expense of cornstarch to establish 6 concentrations of STTD P from 1.54 to 5.15 g/kg in increments of 0.62 g/kg at a constant Ca:total P of 1.52:1.0. Diets were fed to 936 pigs (average initial BW of 19 kg) in 240 pens for 20 replicate pens of barrows and 20 replicate pens of gilts per diet. As STTD P increased from 1.54 to 5.15 g/kg of the diet for d 0 to 14, 14 to 28, and 0 to 28, the ADG, ADFI, and G:F increased ( < 0.01). Barrows gained and ate more ( < 0.05) than gilts during d 14 to 28 and 0 to 28. There was no interaction between sex and STTD P concentration for any of the growth performance response criteria. There were both linear and quadratic increases ( < 0.05) in mineral density and content of ash, Ca, and P in the femur expressed as a percentage of dry, fat-free metacarpal as dietary STTD P increased. Furthermore, the maximum load of the femur and mineral density and content and maximum load as well as the Ca and P expressed as a percentage of metacarpal ash linearly increased ( < 0.01) with increasing dietary concentrations of STTD P. There were both linear and quadratic increases ( < 0.01) in apparent digestibility and retention of P with increasing concentrations of STTD P in the diets. Digestibility and retention of Ca linearly ( < 0.01) increased with increasing dietary concentrations of STTD P. Breakpoints determined from nonlinear broken-line regression analyses revealed estimates of 4.20 ± 0.102, 3.20 ± 0.036, or 3.87 ± 0.090 g/kg for ADG during d 0 to 14, 14 to 28, or 0 to 28, respectively. Corresponding estimates using G:F as the response criterion were 4.34 ± 0.146, 3.38 ± 0.139, or 4.08 ± 0.195 g/kg. When mineralization of the femur was used as criteria of response, estimates of STTD P requirement were 4.28, 4.28, or 4.34, g/kg for mineral density, mineral content, or maximum load, respectively. Using mineralization of the metacarpal as criteria of response, estimates of STTD P requirement ranged from 3.5 to 5.0 g/kg depending on the metacarpal response criteria. The study provided empirical estimates of STTD P requirements of 20- to 40-kg pigs.

Quantitative relationships between standardized total tract digestible phosphorus and total calcium intakes and their retention and excretion in growing pigs fed corn-soybean meal diets.

An experiment was conducted to determine the quantitative relationships between standardized total tract digestible P (STTD P) and total Ca intakes with their retention and excretion by growing pigs fed corn-soybean meal diets. Forty-eight crossbred barrows (BW = 22.7 ± 2.9 kg) were allotted to 1 of 8 diets, housed individually in pens for 3 wk, and then moved to metabolism crates and allowed 4 d for adaptation and 5 d for collection of urine and fecal samples. Eight corn-soybean meal diets were formulated for similar NE, fat, and AA concentrations but to increase the STTD P from 0.16 to 0.62% using monocalcium phosphate. Dietary treatments were formulated for a constant Ca:STTD P ratio (2.2:1). The STTD P intake increased (P < 0.001) from 64 to 242% of the daily requirement (4.59 g/d of STTD P). Fecal and total excretion of P and Ca were linearly associated with mineral intake (P < 0.001). Constant urinary P excretion of 0.03 g/d P was observed, but at 4.96 g/d of STTD P intake, the urinary P excretion increased (P < 0.001). In contrast, Ca excretion in urine decreased (P < 0.001) with Ca intake, but constant excretion of 0.40 g/d Ca was reached at 17.97 g/d of Ca intake. The daily intakes of STTD P and Ca moderately explained the variation in urinary excretion of P (R2= 0.41) and Ca (R2= 0.64). The absorption and retention of P increased linearly (P< 0.001) with dietary P intake, whereas absorption and retention of Ca showed a quadratic response (P < 0.001). Absorption and retention of P and Ca were highly predictable from the STTD P and Ca intakes, with of 0.87 and 0.90, respectively. The femur mineral content (FMC) increased by 2.71 g with STTD P intake (P < 0.001) but reached a plateau (29.54 g of FMC) at 8.84 g/d of STTD P intake. The FMC was highly predictable from the STTD P intake (R2 = 0.89). The FMC affected the urinary P excretion ( P< 0.01), but moderately (R2= 0.19) explained the variation in urinary P. In conclusion, constant excretion of P in urine was observed but excretion increased linearly at STTD P intake levels above the requirement for maximum growth of growing pigs. The FMC increased with STTD P intake, but a plateau was reached at a STTD P intake level above the requirement. Dietary STTD P was used for growth and accumulated in bones until a plateau was reached and excess was excreted in urine. The predictability of P and Ca excretion in urine from the dietary STTD P and Ca intakes was moderate.

Effects of a novel bacterial phytase expressed in Aspergillus Oryzae on digestibility of calcium and phosphorus in diets fed to weanling or growing pigs

In 2 experiments, 48 weanling (initial BW: 13.5 ± 2.4 kg, Exp. 1) and 24 growing pigs (initial BW: 36.2 ± 4.0 kg, Exp. 2) were used to determine effects of a novel bacterial 6-phytase expressed in Aspergillus oryzae on the apparent total tract digestibility (ATTD) of phosphorus and calcium in corn-soybean meal diets fed to weanling and growing pigs. In Exp. 1 and 2, pigs were randomly allotted to 6 dietary treatments using a randomized complete block design and a balanced 2 period changeover design, respectively. In both experiments, 6 diets were formulated. The positive control diet was a corn-soybean meal diet with added inorganic phosphorus (Exp. 1: 0.42 and 0.86% standardized total tract digestible phosphorus and total calcium, respectively; Exp. 2: 0.32 and 0.79% standardized total tract digestible phosphorus and total calcium, respectively). A negative control diet and 4 diets with the novel phytase (Ronozyme HiPhos, DSM Nutritional Products Inc., Parsippany, NJ) added to the negative control diet at levels of 500, 1,000, 2,000, and 4,000 phytase units (FYT)/kg were also formulated. In Exp. 1, the ATTD of phosphorus was greater (P < 0.01) for the positive control diet (60.5%) than for the negative control diet (40.5%), but increased (linear and quadratic, P < 0.01) as phytase was added to the negative control diet (40.5% vs. 61.6%, 65.1%, 68.7%, and 68.0%). The breakpoint for the ATTD of phosphorus (68.4%) was reached at a phytase inclusion level of 1,016 FYT/kg. In Exp. 2, the ATTD of phosphorus was greater (P < 0.01) for the positive control diet (59.4%) than for the negative control diet (39.8%) and increased (linear and quadratic, P < 0.01) as phytase was added to the negative control diet (39.8% vs. 58.1%, 65.4%, 69.1%, and 72.8%). The breakpoint for the ATTD of phosphorus (69.1%) was reached at a phytase inclusion level of 801 FYT/kg. In conclusion, the novel bacterial 6-phytase improved the ATTD of phosphorus and calcium in both weanling and growing pigs. The optimum level of inclusion for this phytase is 800 to 1,000 FYT/kg of complete feed to maximize ATTD of phosphorus and calcium in weanling and growing pigs.