Phosphorus bioavailability, growth performance, and nutrient balance in pigs fed high available phosphorus corn and phytase

Three experiments were conducted to evaluate P bioavailability, growth performance, and nutrient balance in pigs fed high available P (HAP) corn with or without phytase. The bioavailability of P in normal and HAP corn relative to monosodiumphosphate (MSP) for pigs was assessed in Exp. 1. In a randomized complete block design, 96 pigs (average initial BW 9.75 kg) were fed eight diets for 28 d. The reference and test diets were formulated by adding P as MSP, HAP, or normal corn at 0, 0.75, or 1.5 g/kg to a corn-starch-soybean meal basal diet (2.5 g/kg P) at the expense of cornstarch. Plasma inorganic P concentration responded linearly (P < 0.05) to supplemental P intake. Estimates of P bioavailability from HAP andnormal corn when plasma P was regressed on supplemental P intake were 46 and 33%, respectively. In Exp. 2 and 3, pigs were fed corn-soybean meal-based diets containing HAP corn or normal corn and 0 or 600 units of phytase per kilogram in a 2 x 2 factorial arrangement (two corn sources and two levels of phytase). In Exp. 2, 48 crossbred pigs (barrow:gilt, 1:1) averaging 9.25 kg were used to evaluate growth performance. There were no detectable interactions between corn source and phytase for any of the performance criteria measured. Pigs receiving normal corn had the lowest (P < 0.05) BW and rate of gain. Feed efficiency was lower (P < 0.05) in pigs fed normal compared with those fed the HAP corn phytase-supplemented diet. In Exp. 3, 24 crossbred barrows averaging 14.0 kg were used to evaluate nutrient digestibility. There were no detectable interactions between corn and phytase for any of the N and Ca balance criteria. Nitrogen and Ca retention were improved in pigs receiving HAP corn with phytase (P < 0.05). Retention and digestibility of P was lowest (P < 0.01) for pigs on normal corn diet without phytase. The percentage of P digested and retained was improved and fecal P excretion lowered (P < 0.05) by feeding HAP corn.The results of this study indicate that the bioavailability and balance of P in HAP corn is superior to that of normal corn. The addition of 600 phytase units (Natuphos 600, BASF) to HAP corn-based diets further improved P digestibility and reduced P excretion in pigs.     

Growing-finishing performance and carcass characteristics of pigs fed normal and genetically modified low-phytate corn

A genetically modified corn hybrid homozygous for the lpa1 allele, containing low phytate (LP), and its nearly isogenic equivalent hybrid (normal) were compared in two experiments with growing-finishing swine. In Exp. 1, 210 barrows (27 kg) were allotted to one of six dietary treatments with two corn hybrids (LP and normal) and three P feeding regimens. There were five replicate pens (seven pigs/pen) per treatment. Treatments consisted of diets that were supplemented with P throughout the growing-finishing period (.2% P and .15% supplemental P during growing and finishing phases, respectively) or only during the growing phase (.2% supplemental P) or that were not supplemented with P throughout the growing-finishing period. Performance at the end of the growing phase was based on a 2 x 2 factorial arrangement of treatments with two corn hybrids and two levels of added P (0 and .2%). This resulted in 10 replicates for the treatments supplemented with .2% P. The finishing phase (73 to 112 kg) was a 2 x 3 factorial arrangement of treatments with the two types of corn and three regimens of added P during the finishing period. Breaking load (BL) and ash of the fourth metacarpal were evaluated from one pig/pen at the end of the growing phase and from all pigs after slaughter. Pigs fed the LP corn diet without added P had greater body weight gain, feed efficiency, BL, and ash content of the fourth metacarpal than pigs fed the normal corn diet without added P. Performance was similar between pigs fed the LP diet without added P and pigs fed LP and normal corn with added P. In Exp. 2, 1,092 gilts (34 kg body weight) were allotted by weight in a commercial facility to one of three treatments: 1) normal corn/soybean meal diet containing .29% and .22% available P during the growing and finishing phases, respectively; 2) LP corn/soybean meal diet with the same available P level as Treatment 1; and 3) same as Treatment 2 for 8 wk, then no inorganic P supplementation during the finishing phase. All pigs were slaughtered at approximately 122 kg. There were no significant differences in growing-finishing performance or BL among treatments. However, pigs fed diets containing LP corn possessed carcasses with less backfat and a higher percentage of lean (P < .01). These results confirm that the P in LP corn is available to the pig and suggest that pigs fed diets containing this genetically modified corn will have more desirable carcasses.     

Calcium, phosphorus, and amino acid digestibility in low-phytate corn, normal corn, and soybean meal by growing pigs

Nine growing barrows were equipped with a T-cannula in the distal ileum and used to determine apparent ileal (AID) and apparent total-tract digestibility (ATTD) coefficients of Ca and P in low-phytate corn, normal corn, soybean meal, and in diets where soybean meal was mixed with low-phytate corn or normal corn. The AID and the standardized ileal digestibility coefficients (SID) of CP and AA also were determined. The animals (initial BW = 29.3 +/- 1 kg) were allotted to a 9 x 9 Latin square with nine diets and nine periods. Three diets contained low-phytate corn, normal corn, and soybean meal as their sole source of CP, AA, Ca, and P, respectively. Three additional diets were identical to these diets except that limestone and monosodium phosphate were added. Two diets contained low-phytate corn or normal corn and soybean meal, limestone, and monosodium phosphate, and the final diet was a N-free diet. The AID and ATTD of Ca were higher (P < 0.05) for low-phytate corn than for normal corn (70.0 and 69.1% vs. 47.4 and 49.6%, respectively). The AID and ATTD for Ca in soybean meal (50.9 and 46.7%, respectively) did not differ from values for normal corn but were lower (P < 0.05) than for low-phytate corn. The AID and ATTD for P from low-phytate corn (56.5 and 54.5%, respectively) were greater (P < 0.05) than from normal corn (28.3 and 28.8%, respectively), whereas soybean meal had intermediate AID and ATTD for P (37.2 and 38.0%, respectively). The AID and ATTD of P increased (P < 0.05) when monosodium phosphate was added to normal corn (44.9 and 49.8%, respectively) and soybean meal (49.6 and 46.2%, respectively), but adding monosodium phosphate to low-phytate corn, did not alter either AID (49.7%) or ATTD (50.7%) of P. No differences between AID and ATTD for Ca or P within the same diet were observed. The AID of Arg, Asp, Gly, Ile, Lys, Phe, Thr, and Val were greater (P < 0.05) in low-phytate corn than in normal corn. The AID of all AA in soybean meal were greater (P < 0.05) than in both types of corn, with the exception of Ala, Cys, Leu, and Met. The SID of Lys, Phe, and Thr were higher (P < 0.05) in low-phytate corn than in normal corn. Because low-phytate corn has a higher digestibility of Ca and P, less inorganic Ca and P need to be supplemented to diets containing low-phytate corn than to those containing normal corn, and P excretion may be decreased when low-phytate corn is used in the diet.     

The effectiveness of an Escherichia coli phytase in improving phosphorus and calcium bioavailabilities in poultry and young pigs.

The effectiveness of an Escherichia coli phytase in comparison with a commercially available Aspergillus phytase in improving the bioavailability of phosphorus in broilers, layers and young pigs was studied in three separate experiments. Three basal diets, marginally deficient in dietary P mainly provided as phytate, were formulated. Both phytases were added to the diets at the rate of 500 U/kg diet. The phytases significantly (P < or = 0.05) improved the availability of phytate P to broilers, layers and young pigs. Aspergillus and E. coli phytases enhanced the pre-caecal digestibility of P by 11 and 29% for broilers and 18 and 25% for layers, respectively. Total tract digestibility of P (P balance) was also enhanced but with smaller magnitude. In pigs, total tract digestibility of P was improved by 33 and 34% by Aspergillus and E. coli phytases, respectively. Under the conditions of this study, it was observed that E. coli consistently, though with small magnitude in layers and pigs, enhanced the availability of phytate P at the same range or slightly better than Aspergillus phytase. It was only in pigs that the availability of Ca was significantly (P < or = 0.05) improved by addition of both phytases. It can be concluded that E. coli phytase is highly effective in improving the bioavailability of phytate P to broilers, layers and young pigs. This seems to be based on the high proteolytic stability of the enzyme in the digestive tract, as shown recently.     

Evaluation of NutriDense low-phytate corn and added fat in growing and finishing swine diets

Two experiments were conducted to evaluate the effects of NutriDense low-phytate corn in conjunction with increasing added dietary fat on growing and finishing pig performance. Diets in both experiments were corn-soybean meal-based, with yellow dent or NutriDense low-phytate corn and 0, 3, or 6% added choice white grease arranged in a 2 x 3 factorial design. There were 25 to 28 pigs per pen and 7 pens (replications) per treatment in both experiments. In Exp. 1, a total of 1,162 gilts with an initial BW of 44.6 kg were used in a 28-d growth study. A constant true ileal digestible (TID) Lys:ME ratio of 2.80 g/Mcal and available P:ME ratio of 0.90 g/Mcal were maintained in all treatment diets. Overall (d 0 to 28), there were no corn source x added fat interactions (P >/= 0.79). Regardless of corn source, ADG and G:F increased (linear, P = 0.03) with increasing added fat. There were no differences (P >/= 0.34) in pig growth performance between those fed NutriDense low-phytate or yellow dent corn. In Exp. 2, a total of 1,128 gilts with an initial BW of 81.6 kg were used in a 28-d growth study. A constant TID Lys:ME ratio of 2.15 g/Mcal of ME and available P:ME ratio of 0.75 g/Mcal were maintained in all treatment diets. Overall (d 0 to 28), there was a tendency (P = 0.07) for a corn source x added fat interaction for G:F, which can be explained by the improved G:F in pigs fed yellow dent corn only when 6% fat was added to the diet, whereas G:F was improved at both 3 and 6% added fat in pigs fed NutriDense low-phytate corn. There were no differences (P >/= 0.18) in growth performance between pigs fed NutriDense low-phytate or yellow dent corn. These results indicate that increasing added fat improved growth performance regardless of the corn source. In addition, growth performance was similar for pigs fed NutriDense low-phytate or yellow dent corn.     

Enhancement of phosphorus utilization in growing pigs fed phytate-rich diets by using rye bran.

Some cereal by-products, such as bran, exhibit a high phytase activity that may enhance phytate P digestibility. This was studied in growing pigs fed a phytase-rich (1,200 IU/kg) diet containing 20% rye bran. The trial involved 12 animals; six were fed a control diet and six were fed a diet containing rye bran for 2 mo. Both diets contained the same levels of energy, protein, Ca (.7%) and total P (.4%). No inorganic P was added; thus, the dietary P was mainly phytic. Pigs fed the control diet, in contrast to those fed the diet containing rye bran, developed a P deficiency, as indicated by hypophosphatemia, hypophosphaturia, hyperhydroxyprolinuria, hypercalcemia, and hypercalciuria. Phosphorus from the rye bran diet was more completely absorbed (55 vs 36%) and retained (50 vs 36%) than that from the control diet. Calcium absorption was equal for the two diets, but Ca retention was higher in pigs fed rye bran than in controls. Pigs fed the rye bran diet showed greater bone density, ash content, and bending moments than controls. In conclusion, high dietary phytase levels or phytase-rich by-products increased phytate P availability and consequently improved bone scores.     

Relative bioavailability of phosphorus in inorganic phosphorus sources fed to growing pigs

The relative bioavailability of P in 5 sources of inorganic P was determined using growing pigs. The 5 sources of inorganic P were dicalcium phosphate (DCP), monocalcium phosphate (MCP) containing 50% MCP (MCP50), MCP containing 70% MCP (MCP70), MCP containing 100% MCP (MCP100), and monosodium phosphate (MSP). A total of 11 diets were formulated. The basal diet was formulated to contain 0.10% P, and 10 additional diets were formulated by adding 0.07 or 0.14% P from each of the 5 P sources to the basal diet. Growing pigs (n = 44; initial BW: 16.8 ± 4.3 kg) were individually housed and randomly allotted to the 11 experimental diets. Feed was provided on an ad libitum basis throughout the 28-d experimental period. At the conclusion of the experiment, all pigs were killed, and 4 bones (i.e., the third and fourth metacarpals on both front feet) were harvested. Bone-breaking strength, bone ash, and Ca and P concentrations were determined. The concentration of bone ash increased (P < 0.05) as MCP50, MCP70, MCP100, or MSP were added to the basal diet, and the concentration of bone P also increased (P < 0.05) as MCP70, MCP100, or MSP were added to the basal diet. The relative bioavailability of P in each of the feed phosphates was determined using slope ratio methodologies based on breaking strength, and expressed relative to MSP. The slope of the regression line for diets containing MSP or MCP100 was steeper (P < 0.05) than the slope for pigs fed the diet containing DCP, but not different (P > 0.05) from that of pigs fed diets supplemented with MCP50 or MCP70. In conclusion, P in MSP and MCP100 is more bioavailable than P in DCP, but there were no differences within MCP sources.     

Low-phytic acid corn improves nutrient utilization for growing pigs.

Thirty-five crossbred barrows averaging 14.5 kg initial BW were used in a 5-wk experiment to compare the P availability and nutritional value of a low-phytate hybrid corn (LPC, 0.26% total P, 0.08% phytic acid P) homozygous for the lpa 1-1 allele with a nearly isogenic normal hybrid corn (NC, 0.25% total P, 0.20% phytic acid P). The pigs were fed individually twice daily in metabolism pens. Three semipurified diets were created in which corn was the only source of phytate. Diet 1 contained 72% NC, 0.15% estimated available P (aP) and 0.55% Ca. Diet 2 contained 72% LPC, 0.24% aP, and 0.55% Ca. The only differences between Diets 1 and 2 were the source of corn and the levels of aP. No inorganic P (iP) was added to these diets in order to measure the animal response to the different levels of aP in the corn hybrids. Diet 3 was NC Diet 1 supplemented with iP to equal the level of aP in LPC Diet 2. Diets 4 and 5 were practical corn-soybean meal diets formulated with each corn to meet all minimum nutrient requirements and contained 0.30% aP and 0.65% Ca. For the semipurified diets, pigs fed LPC Diet 2 had higher (P < 0.01) growth performance, bone breaking strength, P absorption and retention, Ca absorption and retention, and N retention than pigs fed NC Diet 1. However, when the NC diet was supplemented with iP to equal the aP in the LPC diet, most criteria were similar (P > or = 0.2), indicating an equal nutritional value for both corn hybrids after adjusting for phytate level. The only treatment difference, other than P excretion, between the practical corn diets supplemented with soybean meal was a higher (P < 0.05) bone breaking strength for pigs fed LPC Diet 5 compared with NC Diet 4. The use of LPC in pig diets reduced P excretion in swine waste by 50 and 18.4% in the semipurified and practical diets, respectively, compared with NC. Using our in vitro procedure designed to simulate the digestive system of the pig, the availability of P for pigs was estimated at 56% for LPC and 11% for NC.     

Effect of low-phytate barley or phytase supplementation to a barley-soybean meal diet on phosphorus retention and excretion by grower pigs

Two studies were conducted to determine the effect of diets containing low-phytate barley or supplemented with phytase on P balance and excretion in grower pigs. In Exp. 1, eight 32-kg barrows were assigned to a repeated, 4 x 4 Latin square design and fed 4 diets that contained 96% barley: normal-phytate hulled barley (HB), low-phytate hulled barley (LPHB), normal-phytate hull-less barley (HLB), and low-phytate hull-less barley (LPHLB). The barley cultivars contained 0.16, 0.05, 0.24, and 0.03% phytate, respectively. Inorganic P (iP) was added to the HB and HLB diets to meet the 1998 National Research Council recommendation of available P (aP, 0.23%), whereas LPHB and LPHLB contained sufficient aP. The diets were fed at 2.5 times the maintenance requirement for ME. The apparent total tract digestibilities (ATTD) of P did not differ between the hulled and hull-less barley diets, but P retention (%) and excretion were greater in pigs fed the hull-less barley diets (P < 0.05). The ATTD of P was greater and P excretion was 35% lower in pigs fed the low-phytate compared with the normal-phytate diets (P < 0.001). The amount of P retained (g/d) was greater (P < 0.001) in pigs fed low-phytate barley, reflecting an ATTD of P of 65 and 49% for low-phytate and normal-phytate barley, respectively (P < 0.001). In Exp. 2, eight 21-kg barrows were assigned to a repeated, 4 x 4 Latin square design and fed 4 diets based on barley and soybean meal (SBM): HB-SBM, HB-SBM + iP, HB-SBM + phytase, and LPHB-SBM. The HB-SBM and HB-SBM + phytase diets were deficient in aP, whereas the HB-SBM + iP and LPHB-SBM diets had adequate aP. The feeding regimen was similar to that of Exp. 1. Adding iP to the HB-SBM diet did not affect the ATTD but increased the amount of P retained (g/d) and excreted (P < 0.001). The ATTD and amount of P retained (g/d) did not differ among pigs fed the HB-SBM + iP, HB-SBM + phytase, and LPHB-SBM diets. However, pigs fed the HB-SBM + phytase and LPHB-SBM diets excreted 32 and 29% less P, respectively, than pigs fed the HB-SBM + iP diet (P < 0.05), confirming that low-phytate barley is as effective as supplemental phytase in improving P digestibility and utilization and decreasing P excretion in grower pigs.     

Nutritional value of quality protein maize for starter and finisher swine.

Growth trials with starter (n = 120, 6.8 kg initially, 28 d of age, Exp. 1) and finisher (n = 70, 59 kg initially, Exp. 2) pigs were conducted to compare quality protein maize (QPM, .40% lysine) and normal corn (.31% lysine) in simple corn-based diets containing the same levels of soybean meal. In Exp. 1, pig performance was similar (P greater than .10) on all diets, regardless of the level of soybean meal, suggesting that QPM and normal corn have similar feeding value in lysine-adequate (.99 to 1.11%) diets. In Exp. 2, less soybean meal was needed in QPM than in normal corn diets to maximize performance; increasing soybean meal from 10.8 to 13.8% improved rate (P less than .05) and efficiency (P less than .01) of gain of pigs fed normal corn diets but had no effect on performance of pigs fed QPM diets. A QPM-based diet containing 6% soybean meal and supplemental lysine and tryptophan failed to maximize feed efficiency, but growth rate was equal to that obtained on the normal corn diet with 13.8% soybean meal. The apparent fecal digestibility of GE and ileal digestibility of N were similar for QPM and normal corn, but apparent ileal digestibility of most essential amino acids was slightly higher for QPM (Exp. 3). Experiment 4 compared apparent digestibilities of QPM, conventional opaque-2 corn and two high-protein corns. Digestibilities differed (P less than .05) among the corns, but the absolute differences were small and were likely due to differences in amino acid content of the corns.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of graded doses and a high dose of microbial phytase on the digestibility of various minerals in weaner pigs

An experiment with 224 weaner pigs (initial BW of 7.8 kg) was conducted to determine the effect of dose of dietary phytase supplementation on apparent fecal digestibility of minerals (P, Ca, Mg, Na, K, and Cu) and on performance. Four blocks, each with 8 pens of 7 pigs, were formed. Eight dietary treatments were applied to each block in the 43-d experiment: supplementation of 0 (basal diet), 100, 250, 500, 750, 1,500, or 15,000 phytase units (FTU) or of 1.5 g of digestible P (dP; monocalcium phosphate; positive control) per kilogram of feed. The basal diet, with corn, barley, soybean meal, and sunflower seed meal as the main components, contained 1.2 g of dP per kilogram of feed. Fresh fecal grab samples were collected in wk 4 and 5 of the experiment. Average daily feed intake, ADG, G:F, and digestibility of all of the minerals increased (P < 0.001) with increasing phytase dose. Digestibility of P increased from 34% in the basal diet to a maximum of 84% in the diet supplemented with 15,000 FTU, generating 1.76 g of dP per kilogram of feed. At this level, 85% of the phytate phosphorus was digested, compared with 15% in the basal diet. Compared with the basal diet, digestibility of the monovalent minerals increased maximally at 15,000 FTU, from 81 to 92% (Na) and from 76 to 86% (K). In conclusion, phytase supplementation up to a level of 15,000 FTU/kg of a dP-deficient diet improved performance of weaner pigs and digestibility of minerals, including monovalent minerals. Up to 85% of the phytate-P was digested. Thus, dietary phytase supplementation beyond present day standards (500 FTU/kg) could further improve mineral use and consequently reduce mineral output to the environment.     

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

This study reevaluated the method of regressing of total P output against dietary P intake to simultaneously estimate true P digestibility and endogenous P loss in growing pigs fed either conventional or low-phytate soybean meal (SBM). Four isocaloric diets were formulated to contain increasing concentrations of each type of SBM (8 diets total), and therefore contained increasing concentrations of dietary P. Dietary P and Ca concentrations were deficient because they were supplied solely by SBM, and Ca:total P ratios were less than 1:1. Sixteen barrows (initial BW 17.7 +/- 1.8 kg) were surgically fitted with a simple T-cannula at the distal ileum, randomly assigned to metabolism crates, and fed the experimental diets in a replicated 8 x 8 Latin square design. Feed was provided at 90 g/kg of BW(0.75) and fed in 2 equally sized meals at 0800 and 2000, with diets containing Cr sesquioxide (3 g/kg) as an indigestible marker. As the P concentration increased from 0.9 to 3.9 g/kg of DM, the apparent prececal P digestibility increased for conventional SBM (P < 0.05), but no relationship was observed for low-phytate SBM. The output of total P [mg/(kg of BW(0.75).d)], either prececal or total tract, exhibited a linear relationship (P < 0.01) with increasing P intake. However, a quadratic response (P = 0.02) was also detected for total tract P output from pigs fed low-phytate SBM. True P digestibility was not different between prececal and total tract collection sites (P > 0.10), but was greater (P < 0.01) for low-phytate SBM (62.6%) compared with conventional SBM (44.5%). Endogenous P estimates were not different between the SBM varieties and averaged 4.83 mg/(kg of BW(0.75).d). However, endogenous P estimates were highly variable between individual animals and, therefore, were not significantly different from zero. In this study, estimates of endogenous P loss from pigs were relatively low compared with previously reported values, and evidence of nonlinearity in P output was observed. These results suggest that the difference in true P digestibility between conventional SBM and low-phytate SBM is influenced by dietary phytate content when growing pigs are fed P-deficient diets.     

Novel procedure for estimating endogenous losses and measurement of apparent and true digestibility of phosphorus by growing pigs

An experiment was conducted to evaluate a novel procedure for estimating endogenous losses of P and for measuring the apparent total tract digestibility (ATTD) and true total tract digestibility (TTTD) of P in 5 inorganic P sources fed to growing pigs. The P sources were dicalcium phosphate (DCP), monocalcium phosphate (MCP) with 50% purity (MCP50), MCP with 70% purity (MCP70), MCP with 100% purity (MCP100), and monosodium phosphate (MSP). A gelatin-based, P-free basal diet was formulated and used to estimate endogenous losses of P. Five P-containing diets were formulated by adding 0.20% total P from each of the inorganic P sources to the basal diet. A seventh diet was formulated by adding 0.16% P from MCP70 to the basal diet. All diets were fed to 7 growing pigs in a 7 x 7 Latin square design, and urine and feces were collected during 5 d of each period. The endogenous loss of P was estimated as 139 +/- 18 mg/kg of DMI. The ATTD of P in MSP was greater (P < 0.05) than in DCP, MCP50, and MCP70 (91.9 vs. 81.5, 82.6, and 81.7%, respectively). In MSP, the TTTD of P was 98.2%. This value was greater (P < 0.05) than the TTTD of P in DCP, MCP50, and MCP70 (88.4, 89.5, and 88.6%, respectively). The ATTD and the TTTD for MCP70 were similar in diets formulated to contain 0.16 and 0.20% total P. Results from the current experiment demonstrate that a P-free diet may be used to measure endogenous losses of P in pigs. By adding inorganic P sources to this diet, the ATTD of P can be directly measured and the TTTD of P may be calculated for each source of P.     

Effects of pelleting and storage of a complex nursery pig diet on lysine bioavailability

The effects of pelleting and storage of a complex nursery pig diet (28% lactose and 1.4% lysine) on lysine bioavailability were assessed in a chick bioassay. The nursery diet was steam-conditioned at 60 degrees C for 45 s and then pelleted through a 5-mm die with a depth of 38 mm. Samples of meal and pelleted diet were placed in metallic feeders in an occupied nursery facility for 1 wk (warm) or were stored at 4 degrees C (cool). For the standard-curve bioassay, a total of 144 8-d-old chicks were offered the following dietary treatments: 1 to 3) a basal diet (lysine deficient) and two levels (.08 and .16%) of added lysine (from L-lysine-HCl); 4 and 5) two positive controls (.7% added lysine with or without 10% of the nursery diet); and 6 to 9) basal diet plus 10% of one of the four nursery diet samples (meal or pellet stored cool or warm for 1 wk). Pelleting had no effect (P>.10) on lysine bioavailability, probably because pelleting conditions (temperature, humidity, and pellet size) were not aggressive enough to result in detectable effects on lysine utilization. However, storage in the nursery facility for 1 wk reduced (P<.03) lysine bioavailability by an average of 10%. No significant (P>.10) interactions were observed. Furthermore, true digestibility of lysine in the four pig diet samples was estimated in a cecectomized cockerel digestibility assay using 15 adult Single-Comb White Leghorn cockerels. Lysine digestibility in all samples was high (average of 94%) and was not affected (P>.10) by treatment. We conclude that the pelleting conditions used in our experiments did not decrease lysine utilization. More research is needed to define thermal processing conditions that might cause protein quality deterioration. However, typical warm and humid environmental conditions encountered in modern nursery facilities have a negative effect on protein quality of diets rich in reducing sugars and lysine.     

Nutritional value of quality protein maize and food corn for starter and growth pigs

Growth traits with starter and grower pigs and a digestion trial were conducted to compare the nutritional value of Quality Protein Maize (QPM), food corn and conventional feed corn. The QPM, food and feed corn contained .45, .31 and .29% lysine, respectively. The growth trials evaluated a QPM-soybean meal diet formulated on a lysine basis (.96% in starter and .7% in grower diets) and four diets arranged in a 2 (food corn vs feed corn) X 2 (low vs high soybean meal) factorial. Soybean meal was either added in the same amount as in the QPM diet or was added to provide the lysine content of the QPM diet. Performance was similar for pigs fed food corn and feed corn in both trials. The QPM diets resulted in greater performance than food and feed corn diets containing the same level of soybean meal supplementation; starter pigs were more (P less than .10) efficient and grower pigs had a higher (P less than .01) rate and efficiency of gain. However, performance of pigs fed the QPM diets was not equal to that of pigs fed isolysinic food and feed corn diets; growth rate was lower (P less than .05) in starter pigs and gain:feed was lower (P less than .05) in grower pigs. Diets in the digestion trial consisted of the corns plus 3.25% casein. Energy digestibility was similar for all diets. Ileal N and amino acid digestibilities were highest for QPM, intermediate for food corn and lowest for feed corn. In most instances, these differences were significant (P less than .05). Apparent biological value was highest (P less than .05) for QPM. These trials indicate that food corn and feed corn have similar nutritional value, and that starter and grower pigs can benefit from the higher protein quality of QPM.     

Comparison of different levels and sources of microbial phytases

Phytases catalyse the hydrolysis of phytate rendering phosphorus (P) available for absorption. Endogenous plant phytases are to some extent present in cereals (depending on species and varieties) while microbial phytases are added to cereal based diets to increase the digestibility of phytate bound P. The present study compared two different microbial phytases. The basal diet was composed of wheat, barley, soybean and rapeseed meal without feed phosphate. The diet was initially expanded, pelleted at 90 °C and crumbled. Phytases were added at 250, 500 and 750 FTU kg^− 1 diet (Aspergillus niger; Phytase 1) and 375 and 750 FYT kg^− 1 diet (Peniophora lycii; Phytase 2). The experiment comprised 6 treatment groups of 6 pigs each kept in metabolism crates and fed one of the 5 test diets or a diet with no added microbial phytase. The diets were fed for 12 days, 5 days for adaptation and 7 days for total collection of faeces and urine. Phosphorus digestibility of the basal diet averaged 43% and increased to 55, 61 and 66% following addition of 250, 500 and 750 FTU/kg of Phytase 1 and 54 and 60% following addition of 375 and 750 FYT/kg of Phytase 2, respectively. In conclusion, equivalent effects were obtained when Phytase 2 was given at 1.5 times the doses of Phytase 1.     

生长猪基础饲粮组成对磷酸氢钙和磷酸二氢钙中磷的全肠道真消化率的影响

本试验旨在研究生长猪基础饲粮组成对磷酸氢钙(DCP)和磷酸二氢钙(MCP)中磷的全肠道真消化率(TTTD)的影响。试验1选用10头平均体重为(30.4±1.8)kg的生长猪,按照10×8不完全拉丁方设计,分别饲喂含有5个DCP添加水平的玉米-豆粕型和含有5个DCP添加水平的小麦-豆粕型饲粮,进行8期消化试验;试验2选用10头平均体重为(30.9±1.5)kg的生长猪,按照10×8不完全拉丁方设计,分别饲喂含有5个M CP添加水平的玉米-豆粕型和含有5个MCP添加水平的小麦-豆粕型饲粮,进行8期消化试验。每期消化试验包括5 d的饲粮适应期和2 d的粪便收集期。结果表明:1)玉米-豆粕型饲粮的总粪磷排泄量极显著高于小麦-豆粕型饲粮(P0.01),小麦-豆粕型饲粮的全肠道可消化磷含量和磷的表观全肠道消化率(ATTD)极显著高于玉米-豆粕型饲粮(P0.01)。饲粮添加DCP和MCP线性增加总粪磷排泄量、全肠道可消化磷含量及磷的ATTD(P0.01)。2)通过使用线性回归法,测得生长猪采食玉米-豆粕型和小麦-豆粕型饲粮对DCP中磷的TTTD分别为82.33%和82.88%,生长猪采食玉米-豆粕型和小麦-豆粕型饲粮对MCP中磷的TTTD分别为85.88%和84.62%。由此可见,生长猪基础饲粮组成对DCP和MCP中磷的TTTD无显著影响。     

Effect of phytase supplementation to a low- and a high-phytate diet for growing pigs on the digestibilities of crude protein, amino acids, and energy

Supplementation of microbial phytase usually improves the digestibility and utilization of phosphorus in feedstuffs of plant origin. The effect of phytase supplementation on the digestibilities of AA also has been examined, but the results have been inconsistent. This study was carried out to determine the effect of phytase (Natuphos) supplementation, at a rate of 2,000 phytase units/kg, to two basal diets on the apparent ileal digestibilities (AID) of GE, CP, and AA, and on the apparent total-tract digestibilities (ATTD) of CP and GE. The basal diets contained 18% CP and were formulated (as-fed basis) to contain either a low (0.22%) or high content (0.48%) of phytate P. The high-phytate diet contained 20% rice bran, which is a rich source of phytate and has low intrinsic phytase activity. Eight barrows (average initial BW = 40.6 kg), fitted with a simple T-cannula at the distal ileum, were fed the four diets according to a replicated 4 x 4 Latin square design. The pigs were fed twice daily at 0800 and 2000, equal amounts each meal, at a rate of 2.4 times the daily maintenance requirement for ME. Each experimental period comprised 14 d. Ileal digesta were collected from 0800 to 2000 on d 12, 13, and 14. Feces were collected from 0800 on d 8 until 0800 on d 12. Chromic oxide was used as the digestibility marker. The AID of GE, CP, and AA and the ATTD of CP and GE were less in the high- than in the low-phytate diet (P < 0.01). With the exception of glutamic acid, phytase supplementation did not affect (P > 0.10) the AID of CP and AA. There was no effect (P > 0.05) of phytase on the ATTD of CP and GE. These results show that if a response occurs to phytase supplementation, it is independent of the dietary phytate content.     

Influence of dietary phosphorus concentration on the digestibility of phosphorus in monocalcium phosphate by growing pigs

An experiment was conducted to test the hypothesis that the dietary inclusion rate of P does not influence the digestibility of P. The experiment was conducted at 4 experiment stations where the same protocol was followed. A total of 60 growing pigs (initial BW: 22.22 +/- 2.13 kg) were allotted to 6 dietary treatments with 10 replications per treatment. All pigs were placed in metabolism cages that allowed for the total, but separate, collection of urine and fecal materials. Six diets were formulated. The basal diet was based on corn (54.2%), soybean meal (20%), and cornstarch. No inorganic P was used, and the total concentration of P in the basal diet was calculated to be 0.29%. Five additional diets were formulated by adding monocalcium phosphate (MCP) in increments of 0.34% to the basal diet and thereby creating diets that were calculated to contain 0.36, 0.43, 0.50, 0.57, and 0.64% total P, respectively. Ground limestone was also added to these diets to maintain a calculated Ca:P ratio of 1.2:1. The balances of Ca and P and the apparent total tract digestibility (ATTD) of Ca and P were calculated for each diet. The contribution of P from the basal diet was then subtracted from the MCP-containing diets to calculate the balance and ATTD for P in MCP. Results of the experiment showed that the absorption and retention of both Ca and P increased (linear, P < 0.001) with increasing concentrations of Ca and P in the diet. The ATTD for Ca ranged from 62.3 to 66.8% and was not influenced by the dietary concentration of Ca. However, the ATTD for P increased from 38.4 to 65.2% as increasing levels of MCP were added to the diet (linear, P < 0.001). Increasing P intake from MCP increased (linear, P < 0.001) the excretion of P in the feces, but the quantity of P that was absorbed and retained also increased (linear, P < 0.001) as more P from MCP was added to the diet. When measured as a percentage of P intake, P retention was not influenced by the dietary P concentration. The ATTD for P in MCP ranged from 79.5 to 88.5% and was not affected by the concentration of P in the diet. Results of this experiment demonstrated that the digestibility and absorption of P from MCP are not influenced by the dietary concentration of P.     

Methionine requirement of the finishing pig

Two pig experiments were conducted using a methionine (Met)-deficient feather meal-corn-soybean meal basal diet (13% CP; 3,400 kcal ME/kg diet, .126% Met, 456% cystine) supplemented with an amino acid mixture (lysine, tryptophan, histidine, threonine and phenylalanine) to determine the Met requirement of finishing pigs between 50 and 80 kg live weight. Using young chicks in a Met bioavailability growth assay and cecectomized adult cockerels in a Met digestibility assay, the Met-deficient basal diet was found to contain .115% bioavailable and .110% digestible Met. These results gave a bioavailability estimate (relative to DL-Met set at 100%) of 91.3 +/- 2.5% and a true digestibility estimate of 87.0 +/- 2.2% for Met in the basal pig diet. In Exp. 1, 21 crossbred pigs averaging 61 kg initially were individually fed diets containing .115, .165 or .215% bioavailable Met for 21 d. Average daily gain and gain:feed ratio increased quadratically (P less than .05) as level of Met increased. In Exp. 2, 30 crossbred pigs averaging 53 kg were individually fed diets containing .115, .135, .155, .175 or .195% bioavailable Met for 27 d. Daily gain and gain;feed ratio responded linearly (P less than .01) as Met level increased. Based on the results of Exp. 2, the bioavailable Met requirement of finishing pigs in the weight range 50 to 80 kg was estimated to be .182% of the diet. Assuming an 88% bioavailability of Met in commercial diets based on corn and soybean meal, the total Met level needed in practice would be .207%. If 55% of the finishing pig's sulfur amino acid need can be furnished by cystine, the total sulfur amino acid requirement would be .45% of the diet.