Improving phytate phosphorus availability in corn and soybean meal for broilers using microbial phytase and calculation of phosphorus equivalency values for phytase

Two experiments were conducted to determine the effectiveness of Natuphos phytase for improving P availability of soybean meal-based semipurified diets (SP, Experiments 1 and 2) and corn-soybean meal-based diets (CS, Experiment 2) fed to broilers (1 to 21 d). There were 360 and 288 birds fed the SP diets in Experiments 1 and 2, respectively, and 288 birds were fed the CS diets in Experiment 2. Phosphorus equivalency values for phytase were calculated. The basal diets were formulated to contain 0.27% nonphytate P (nP); the SP basal diet contained 0.45% total P (tP) that included 0.17% P as defluorinated phosphate; the CS basal diet contained 0.51% tP that contained 0.12% P as defluorinated phosphate. Both basal diets were supplemented with defluorinated phosphate to provide 0.36, 0.45, of 0.54% nP or with 350, 700, or 1,050 U of phytase/kg diets. Supplementing defluorinated phosphate and phytase linearly increased BW gain (P < 0.001), feed intake (P < 0.001), and percentage ash of dried toes (P < 0.01). Phytase addition increased apparent retention of P (P < 0.02), Ca (P < 0.005 in Experiment 2), and N (P <0.06 in Experiment 2 for CS), increased apparent digestibility of DM (P < 0.04), and linearly decreased (P <0.005) P excretion. In comparison to the 0.45% np diet, P excretion was reduced 42 to 51% by addition of phytase. The addition of defluorinated phosphate linearly decreased apparent retention of P (P < 0.02) and Ca (P < 0.005 in Experiment 2), and increased P excretion (P < 0.007). The average of released P by phytase calculated by solving nonlinear or linear response equations of P and phytase levels for SP diets in Experiments 1 and 2 gave a P equivalency value 1 g P = 1,146 U of phytase. The P equivalency value for CS diets fed only in Experiment 2 was 785 U of phytase = 1 g P as defluorinated phosphate. These studies show that microbial phytase is effective for improving P availability and for decreasing P excretion. Added phytase can also increase Ca and N retention.     

Response of broilers to graded levels of microbial phytase added to maize-soyabean-meal-based diets containing three levels of non-phytate phosphorus

Male 1-d-old broilers (n 920) were given 0, 200, 400, 600, 800, 1000 and 1200 U microbial phytase/kg diet in combination with 2.0, 2.7 or 3.4 g non-phytate P (nP)/kg or 4.0, 5.1 or 5.8 g total P (tP)/kg in a 21 d trial to assess the effectiveness of phytase in a maize-soyabean-meal diet. In addition to the above twenty-one diets, a positive control P diet supplied 4.5 g nP/kg, 6.9 g tP/kg and 10 g Ca/kg. The basal diet contained 230 g crude protein/kg, 8.8 g Ca/kg, 4.4 g tP/kg and 2.0 g nP/kg. Defluorinated phosphate and limestone were used to supply P and Ca. A Ca:tP ratio of 2:1 was maintained except in the positive control diet which had a ratio of 1.45:1. Phytase additions linearly increased (P < 0.01) body-weight (BW) gain, feed intake, toe ash percentage, and apparent retention (% of intake) or total amount (g/bird) of retained Ca and P, and linearly decreased (P < 0.01) P excretion (g/kg of DM intake) at each level of nP with the magnitude of the response inversely related to the level of nP. Above-normal mortality was only observed in the group receiving 2.0 g nP/kg diet without phytase. Adding nP linearly increased (P < 0.01) BW gain, feed intake, toe ash percentage, Ca retention, total amount (g/bird) of P retained, and P excretion, and linearly decreased (P < 0.01) apparent retention (%) of P. Derived linear and non-linear equations for BW gain and toe ash percentage at the two lower nP levels, 2.0 and 2.7 g/kg, were used to calculate P equivalency values of microbial phytase. The results show that 939 U microbial phytase is equivalent to 1 g P from defluorinated phosphate in broilers fed on maize-soyabean-meal diets. The amount of P released per 100 U phytase decreased as the total amount of phytase increased.     

Methane output and lactation response in Holstein cattle with monensin or unsaturated fat added to the diet

We measured effects of continuous vs twice-daily feeding, the addition of unsaturated fat to the diet, and monensin on milk production, milk composition, feed intake, and CO2-methane production in four experiments in a herd of 88 to 109 milking Holsteins. Methane and CO2 production increased with twice-daily feeding, but the CO2:CH4 ratio remained unchanged. Soybean oil did not affect the milkfat percentages, but fatty acid composition was changed. All saturated fatty acids up to and including 16:0 decreased (P < .01), whereas 18:0 and trans 18:1 increased (P < .001). The 18:2 conjugated dienes also increased (P < .01) when the cows were fed soybean oil. Monensin addition to the diet at 24 ppm decreased methane production (P < .01); the CO2:CH4 ratios reached 15, milk production increased (P < .01), and milkfat percentage and total milkfat output decreased (P < .01), as did feed consumption, compared with cows fed diets without monensin (P < .05). Milk fatty acid composition showed evidence of depressed ruminal biohydrogenation: saturated fatty acids (P < .05) decreased and 18:1 increased (P < .001); most of the increase was seen in the trans 18:1 isomer. As with soybean oil feeding, addition of monensin also increased (P < .05) the concentration of conjugated dienes. The monensin feeding trial was repeated 161 d later with 88 cows, of which 67 received monensin in the diet in the first trial and 21 cows were newly freshened and had never received monensin. Methane production again decreased (P < .05), but this time the CO2:CH4 ratio did not change and all other monensin-related effects were absent. The ruminal microflora in the cows that had previously received monensin seemed to have undergone some adaptive changes and no longer responded as before.     

Influence of porcine somatotropin on the phosphorus requirement of finishing pigs: I. Performance and bone characteristics

We conducted two experiments to evaluate the effects of recombinant porcine somatotropin (pST) on the P requirement of finishing pigs. Corn-soybean meal diets with varying levels of P were fed, and Ca was adjusted to maintain a Ca:P ratio of 1.1:1. In Exp. 1, 96 pigs were fed dietary P concentrations of .35, .45, and .65% from 75 to 109 kg BW. One-half of the pigs were injected daily with 4 mg of pST. Pigs treated with pST consumed less feed and gained more efficiently than untreated pigs (P < .01). Increasing the dietary P level produced linear (P < .05) improvements in most metacarpal-metatarsal (MM) and femur traits. Administration of pST increased (P < .02) bone weight, but it reduced (P < .03) bone strength and the percentage of ash. The increases in percentage of ash and ash accretion associated with increasing dietary P were more pronounced in pST-treated pigs than in untreated pigs (pST x P, P < .01). Experiment 2 consisted of 66 pigs fed six dietary P concentrations (.35, .50, .65, .80, .95, and 1.10%) from 72 to 114 kg. One-half of the pigs were injected daily with 4 mg of pST. Pigs treated with pST gained faster and more efficiently (P < .01) but consumed less feed than untreated pigs (P < .01). Increasing the dietary P level improved most of the bone traits. Administration of pST reduced (P < .01) MM strength and percentage ash in the MM and femurs, but it increased (P < .01) femur diameter and wall thickness. Bone strength and percentage ash were reduced in pST-treated pigs fed low dietary P; however, at higher dietary P, these traits were similar to or greater than those in untreated pigs (pST x P, P < .10). Generally, bone traits in pST-treated pigs reached a plateau at higher dietary P concentrations and at higher P intakes compared with those in untreated pigs. These results indicate that pST administration increases the dietary P level that is required to maximize bone traits in finishing pigs.     

Fertilizer calcium as a factor affecting the voluntary intake, digestibility and retention time of pangola grass (Digitaria decumbens) by sheep

1. Pangola grass (Digitaria decumbens) grown with and without calcium fertilizer was cut at three stages of regrowth to measure voluntary intake of dry matter (DM) and digestibility of various components of the dried-grass diet by sheep kept in metabolism crates. To determine the extent of a simple Ca deficiency half the sheep on each diet was supplemented with 1-4 g Ca/d. Retention times of the various dietary components in the reticulo-rumen were also determined. 2. Feeding a Ca supplement had no effect on voluntary intake or digestibility. 3. Ca fertilizer increased the Ca content of the grass from 2-2 to 3-8 g/kg DM and DM digestibility from 0-455 to 0-476 (P less than 0-01) due to an increase in the digestibility of the hemicellulose. 4. Voluntary intake was increased from 38-8 to 43-2 g/kg body-weight0.75 per d by Ca fertilizer due to an 18% reduction in the period of time the DM was retained in the reticulorumen. 5. Regressions relating voluntary intake to DM digestibility for the Ca-fertilized and control grass were significantly different (P less than 0-01). When compared at the same DM digestibility the voluntary intake of the Ca-fertilized grass was 2-6 g/kg body-weight0.75 per d higher than that of the control. 6. It was concluded that Ca fertilizer increased both DM digestibility and voluntary intake as a result of changes in the structural composition of the grass and not by a simple increase in the Ca content of the diet.     

Tropical pasture hay utilization with slaframine and cottonseed meal: ruminal characteristics and digesta passage in wethers

Sixteen mature, ruminally cannulated wethers (average BW = 41 +/- 1 kg) were fed a low-quality hay diet with or without a cottonseed meal (CSM) supplement and the parasympathomimetic agonist slaframine (SF). Treatments were basal diet (Mitchell grass hay, 4.8% CP, 46.8% ADF) available on an ad libitum basis, basal diet plus SF (8 micrograms/kg BW, 2 x daily i.m. injection), basal diet plus CSM (41.0% CP; 100 g/d), or basal diet plus SF and CSM. Treatments were arranged as a 2 x 2 factorial within a replicated 4 x 4 Latin square with 20-d periods followed by a 10-d adjustment during which only the basal diet was fed. All measurements were performed within the final 10 d of each period. Slaframine increased salivary flow by 10 to 35% (P < .07), ruminal fluid dilution rate by 8 to 11% (P < .10), and pH by 3 to 4% (P < .001). A twofold increase (P < .05) in ruminal cellulolytic bacteria numbers occurred in SF-treated wethers. Despite these SF-induced changes in the ruminal environment, whole-tract apparent nutrient digestibility, N and mineral balance, and ruminal VFA concentrations were not changed. Cottonseed meal increased forage intake by 34 to 54% (P < .001) and DM digestibility by 30% (P < .001). Cottonseed meal supplementation of a Mitchell grass hay diet improved nutritional status and attenuated live weight loss.     

Response of pigs to space allocation and diets varying in nutrient density

Three experiments were conducted to determine the main and interacting effects on growth performance of floor space allowance and dietary lysine and energy concentrations for growing-finishing pigs. In each experiment, space allocations of .56 or .78 m2/pig were achieved with 14 or 10 pigs per pen, respectively. In Exp. 1, diets investigated were National Research Council (NRC) recommended nutrient densities, NRC plus 5% added fat (F), NRC plus .15% added L-lysine. HCl (L), and NRC plus fat plus lysine (FL) in a 4 x 2 x 2 factorial arrangement of diets with space and season (winter vs summer). In Exp. 2 and 3, a 2 x 3 factorial treatment arrangement was used to investigate space and diet effects. Diets investigated contained 0, 2.5, or 5% added fat (choice white grease [Exp. 2]; tallow [Exp. 3]) with L-lysine.HCl added to maintain a constant lysine:ME ratio. In Exp.1, pigs given .56 m2/pig vs .78 m2/pig ate less feed (P < .001) and grew slower (P < .001) with no difference in gain:feed ratio or carcass lean percentage. Feed intake was decreased (P < .005) and gain:feed ratio increased (P < .001) for the FL vs L diet. In Exp. 2, pigs given .56 m2/pig vs .78 m2/pig grew slower (P < .001) with a poorer gain:feed ratio (P < .05) and a slower rate of lean gain (P < .05). In Exp. 3, pigs given .56 m2/pig vs .78 m2/pig grew slower (P < .05) with no difference in gain:feed ratio and a slower rate of lean gain (P < .005). There was a linear improvement in ADG (P < .01, Exp. 2; P = .011, Exp. 3) and gain:feed ratio (P < .001, Exp. 2 and 3) with increasing amounts of fat in the diet. The lack of space x diet interactions in these experiments suggests that the reduction in ADG associated with the reduction in ADFI for pigs given less space is independent of dietary lysine and energy concentrations.     

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

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)     

The efficacy of Aspergillus niger phytase in rendering phytate phosphorus available for absorption in pigs is influenced by pig physiological status

We performed an experiment with 112 piglets, 32 growing-finishing pigs, and 12 sows during pregnancy and lactation to test the hypotheses that apparent total tract digestibilities of P and Ca as well as the efficacy of Aspergillus niger phytase in rendering phytate P available in pigs depend on pig physiological status. All pigs were fed diets with identical feedstuff composition either without or with added microbial phytase (Natuphos, 500 FTU/kg diet). The diets contained 6.2 g Ca, 4.8 g total P, and 3.7 g phytate P per kilogram, and intrinsic phytase activity of 120 FTU/kg. The digestibility of P increased by 8.3 percentage units when BW of pigs increased from 30 to 60 kg and then remained stable until 100 kg. Pregnant sows had a lower efficiency of P absorption than piglets and growing-finishing pigs. During lactation, the efficiency of P absorption was 3.4 percentage units higher than during pregnancy but was still 6.6 percentage units lower than for growing-finishing pigs. The efficacy of the phytase in generating digestible P decreased in the order or lactating sows, growing-finishing pigs, sows at the end of pregnancy, piglets, and sows at midpregnancy; the average amounts of generated digestible P were 1.03, .83, .74, .66, and .32 g/kg diet, respectively. The addition of phytase to the diet raised apparent Ca digestibility in the piglets and growing-finishing pigs (by 4.6 and 4.0 percentage units, respectively) but not in the sows. We conclude that in the formulation of swine diets the amount of phytase to be added should be tailored to the target category.     

A multi-element isotopic tracer assessment of true fractional absorption of minerals from formula with additives of calcium, phosphorus, zinc, copper and iron in young piglets

True fractional absorption of minerals was measured to determine the bioavailability of Zn, Fe, Mn and Se from liquid formulas fortified with stepwise additions of Ca and P (as Ca glycerophosphate and carbonate, Ca*P), and Zn, Cu and Fe (as sulfate salts). Growth, deposition of tracers in organs and bone mineral content of femurs as assessed by single photon absorptiometry were measured. Four-day-old piglets (n = 36) were randomly assigned to groups fed a basal diet or additions of Ca*P (Ca = 25, P = 18 g/kg dry diet), Ca*P+Zn (Zn = 0.04 g/kg), Ca*P+Zn+Cu (Cu = 0.007 g/kg) or Ca*P+Zn+Cu+Fe (Fe = 0.008 g/kg). Oral and intravenous administration of extrinsic isotopes of 59Fe, 54Mn, 65Zn, 75Se and 47Ca was followed by fecal monitoring for 15 d and true absorption calculated after accounting for endogenous excretion. Addition of Ca*P+Zn reduced Zn absorption (P < 0.05) and Ca*P+Zn+Cu reduced Fe absorption (P < 0.01), but Mn and Se absorptions were not altered. Uptake of only Zn tracer into heart was significantly different (P < 0.05) among diet groups. Weight gain and linear growth were similar in all groups. Addition of Ca*P produced higher bone mineral density, but its effect on Zn absorption warrants further investigation.     

Effect of acute heat stress on amino acid digestibility in laying hens

An experiment was conducted to determine the effect of acute heat stress exposure on amino acid digestibility in laying hens. A total of 30 commercial laying hens were singly housed in an environmentally controlled facility, fed a standard laying ration, and exposed to a constant thermoneutral temperature (21 C) for 12 d. The hens were then randomly fed one of three diets (10 hens per diet) and exposed to three consecutive temperature periods (8 d each), which consisted of: 1) a constant 21 C temperature, 2) a cycling temperature of 35 C for 12 h and 29 C for 12 h, and 3) a constant 21 C temperature. The three isonitrogenous (18% CP) diets fed were: 1) a corn-soybean meal diet, 2) a corn-soybean meal diet containing 15% meat and bone meal, and 3) a corn-soybean meal diet containing 5% alfalfa meal and 20% wheat bran. Excreta were collected from all hens during the last 4 d of each temperature period and apparent amino acid digestibility was determined. There was a significant diet effect (P < 0.05) on amino acid digestibility. Digestibility of amino acids in Diet 2 (corn-soybean meal/meat and bone meal) was higher (P < 0.05) than in the other two diets. In addition, digestibility of amino acids in Diet 3 (corn-soybean meal/alfalfa meal/wheat bran) was significantly lower (P < 0.05) than in Diets 1 or 2. Heat stress generally had no significant effect on amino acid digestibility except for His and Lys digestibility. Histidine digestibility was higher during the heat stress period than during the initial and recovery thermoneutral periods, whereas Lys digestibility was higher during the heat stress period than during the initial thermoneutral period. These results indicated that acute heat stress (8 d) had no adverse effects on dietary amino acid digestibility in laying hens.     

Technical note: forage in vitro dry matter digestibility as influenced by fiber source in the donor cow diet

Objectives of this study were to determine the influence of five donor cow diets that differed in source of fiber on true in vitro DM digestibility of eight forages. Test forages included two alfalfa (31.2 and 38.3% NDF), corn silage (50.2% NDF), oat forage (48.2% NDF), perennial rye (62.1% NDF), two reed canarygrasses (55.9 and 68.1% NDF), and timothy (68.2% NDF). Sources of fiber in donor cow diets were alfalfa haylage or alfalfa haylage plus either corn cobs, cottonseed hulls, oat hulls, or soy hulls. In addition, the effect of filtering through sintered glass crucibles or filter paper (two replicates each) was evaluated. There were differences (P < .01) among feeds in in vitro DM digestibility, but there were no interactions (P > .05) between test forages and either source of fiber in donor diets or filtration method. There was an interaction between source of fiber in the donor diet and method of filtration (P < .01). Samples inoculated with ruminal fluid from cows fed diets with oat hulls or soy hulls had lower (P < .01) in vitro DM digestibility when filtered on crucibles than on filter paper. Filtration method did not affect (P > .05) in vitro DM digestibility of samples inoculated with ruminal fluid from other diets. The in vitro DM digestibility of samples inoculated with ruminal fluid from cows fed alfalfa haylage was less than the in vitro DM digestibility when other inocula were used. The source of fiber in the donor cow diet and filtration method can affect in vitro DM digestibility, but relative ranking of forages was unaffected by these variables.     

The skeletal calcium/phosphorus ratio: a new in vivo method of determination

We describe a new method for assessing the Ca/P ratio of bone in vivo using gamma-ray photon absorptiometry. The theoretical approach of the method and the estimation of the variance are presented. Two radiation sources, Gd-153 (100 keV), and I-125 (27.5 keV), and a germanium detector were used to determine this ratio. Measurements were made on bone phantoms with different Ca/P ratios; also, the ratio was measured on lamb and sheep tibias, rabbit tibias, and human fingers. Since the accuracy of the method is affected by the amount of fat and collagen in the measurement field, the effect of collagen and fat on the measurements also was investigated. In all cases, the precision of the method, expressed as the coefficient of variation (CV): 100x standard deviation/mean, was near to the theoretical one, ranging from 1.8% to 3.2%. For human fingers, the CV was 3.2%, a value near to the theoretical 2.9% with a dose to the skin ranging from 0.044 to 0.066 mGy, depending on the width of the finger.     

Strategies to improve the nutritive value of rice bran in poultry diets. III. The addition of inorganic phosphorus and a phytase to duck diets

1. In the first of 2 experiments ducklings grown from 2 to 19 d were given diets with 0, 200 or 400 g rice bran, with or without a phytase and with 1 or 3 g inorganic phosphorus (Pi) per kg for rice bran-based diets only. In the 2nd experiment rice bran concentrations were 0, 300 or 600 g rice bran per kg with or without a phytase and 1 g Pi/kg. Ducks were grown from 19 to 40 d of age. 2. In experiment 1, a response to phytase was observed for weight gain and food intake on most diets except those with 200 g rice bran (3 g Pi) and 4.00 g rice bran (1 g P)i/kg. Main effects showed that 400 g rice bran depressed growth rate and food conversion ratio (FCR); increasing Pi depressed food intake, while food phytase increased food intake and growth rate over 2 to 19 d. There were several interactions. Dry matter and P retention were reduced but N digestibility improved when rice bran was increased from 200 g to 400 g/kg at 2 to 10 d of age; apparent metabolisable energy (AME) and calcium retentions were improved, similar results being seen at 10 to 19 d of age. Calcium and P retentions increased with the addition of food phytase and, at 10 to 19 d of age, phytase increased dry matter digestibility. Increasing Pi improved calcium and P retention, but only at 2 to 10 d of age. 3. Tibia ash (g or g/kg) content of bone was lowest on the diet without rice bran and without phytase; Pi concentration had no effect but phytase increased tibia ash on diets with 0 and 200 g rice bran and 1 g Pi/kg. Retention of several minerals in tibia ash declined at the highest rice bran inclusion rate; Pi level and phytase both increased Mg retention. 4. In experiment 2, food intake and growth rate of ducks, but not FCR, declined as rice bran inclusion increased from 0 to 600 g/kg. Phytase improved growth rate but not food intake and FCR on all 3 diets. Dry matter digestibility declined with increasing rice bran inclusion, but AME increased; retention of P and Mg declined but those of Ca and Fe increased. Phytase improved dry matter digestibility and retention of N and P. AME also increased but this was only on diets with 0 and 600 g rice bran/kg. There were reductions of 8% and 10% in P excreted in experiments 1 and 2 respectively when food phytase was added. 5. Tibia ash declined with increasing dietary inclusion of rice bran. Zn and Mn in ash tended to decline and Mg to increase; Ca and P showed no change in concentration in tibia ash. Again, phytase increased tibia ash content in bone. 6. It was concluded that there were a number of unexpected benefits from adding a food phytase to these diets, which resulted in improved nutrient yield and bird performance, although several of the diets appeared to be adequate in available P.     

The feeding value of dry-rolled and steam-flaked corn in finishing diets for feedlot cattle: influence of protein supplementation

We used 80 medium-framed yearling crossbred heifers (357 kg) in a 110-d trial to evaluate the influence of dietary protein level (11 vs 14%) on the feeding value of dry-rolled (DRC) and steam-flaked corn (SFC). All diets contained 1% urea; cottonseed meal (CSM) was the source of supplemental undegradable intake protein (UIP). Steam flaking corn reduced DMI (9%, P < .10) and increased (P < .01) feed efficiency (14%), dietary NEm (13%), and NEg (15%). Steam flaking increased the NEm by 17% and NEg by 19%. Supplemental CSM decreased (P < .10) feed efficiency (7%) and dietary NEm (4%) and NEg (6%). There were no treatment effects (P > .10) on carcass characteristics. Steam flaking corn increased (P < .05) fecal pH and reduced (P < .01) fecal starch. Supplemental CSM increased (P < .01) fecal pH and reduced (P < .01) fecal starch. Four Holstein steers (413 kg) were used in a 4 x 4 Latin square experiment to evaluate treatment effects on digestive function. Steam flaking corn increased (P < .05) flow of nonammonia N (11%, P < .05) and microbial N (15%, P < .01) to the duodenum. Supplemental CSM increased the flow of microbial N (6%, P < .01), feed N (21%, P < .10), and nonammonia N (12%, P < .05) to the duodenum. The UIP value of CSM was 28% for the DRC diet and 52% for the SFC diet. Steam flaking corn increased (P < .01) ruminal starch digestion (26%) and total tract digestibility of OM (17%), N (15%), starch (19%), and GE (17%). Steam flaking increased the DE value of corn by 21%. Supplemental CSM did not influence (P > .10) postruminal or total tract starch digestion. Supplemental CSM decreased (7%, P < .10) the DE value of the diet. We conclude that increasing the postruminal protein supply of a corn-based finishing diet beyond that provided by urea supplementation, alone, will not enhance starch digestion or the energy value of the diet.     

Efficacy of phytase in improving the bioavailability of phosphorus in soybean meal and corn-soybean meal diets for pigs

Four experiments involving 225 pigs were conducted to assess the efficacy of a microbial phytase (FINASE, Alko Ltd. Biotechnology, Rajam?ki, Finland) produced by Aspergillus niger in corn-soybean meal or dextrose-cornstarch-soybean meal-based diets. In two experiments with growing-finishing pigs, fortified corn-soybean meal diets were formulated to be adequate (.50%) or inadequate (.40 or .30%) in P during the growing phase followed by adequate (.40%) or inadequate (.30%) P in the finishing phase. Mono-dicalcium phosphate was the source of supplemental P. Half the diets were supplemented with phytase (500 phytase units/g). Rate and efficiency of gain and bone breaking strength were decreased when P-deficient diets were fed. Phytase supplementation of the low-P diets restored growth rate and feed:gain to levels that approached those of pigs fed the adequate-P control diet. Bone strength was partially restored to that of the controls. In two additional experiments, pigs were fed low-P basal diets in which all the dietary P came from soybean meal or a corn-soybean meal blend. Both diets contained .05% available P. Graded levels of monosodium phosphate were added to these diets, up to .15% added P, to establish a standard curve. Phytase was added to the basal diet at 250, 500, or 1,000 units/g. Growth rate and bone strength improved linearly (P < .01) with added monosodium phosphate and with increasing levels of supplemental phytase. Based on estimates of total and available P intakes, the highest level of phytase (1,000 units/g) increased the bioavailability of the P from 25% in the soybean meal diet to 57% in the phytase-supplemented diet, and from 15% in the corn-soybean diet to 43% in the phytase-supplemented diet. Expressed on the basis of the improvement in phytate P availability, this level of phytase converted approximately one-third of the unavailable P to an available form. The results indicate that the phytase was efficacious in improving the bioavailability of phytate P for pigs.     

Modulation of endothelium-dependent hyperpolarization and relaxation to acetylcholine in rat mesenteric artery by cytochrome P450 enzyme activity

Twelve Hereford steers (average BW = 231 kg) that had previously grazed native rangeland (Range) or irrigated winter wheat pasture (Wheat) were allowed to graze locoweed-infested rangeland from April 1 to June 9, 1994 (six steers/previous grazing treatment). Relative consumption level of locoweed and other forage classes was measured as observed bites per steer. Liver biopsy and whole blood samples were obtained from each steer before and after grazing. Liver samples were analyzed for several minerals by inductively coupled plasma-atomic emission spectroscopy, and whole blood samples were analyzed for Se. Liver concentrations of Ba (P < .001), Cd (P < .001), Ca (P < .01), Cr (P < .01), Ni (P < .001), Na (P < .01), and V (P < .001) were greater and concentrations of Mn (P < .09), P (P < .01), and K (P < .07) were less in Wheat than in Range steers. Liver concentrations of Fe, Mg, S, and Zn and whole blood Se concentrations did not differ (P > .10) between the two groups. Liver concentrations of Cr (P < .04) and Mn (P < .001) were less, and Fe concentrations were greater (P < .01), in samples taken after grazing than in samples taken before grazing of locoweed-infested range. Whole blood Se concentrations decreased (P < .01) from the beginning to the end of the grazing period, but this effect was not related (P > .15) to locoweed consumption. Changes in liver concentrations of minerals were compared relative to consumption levels of all forage classes in the locoweed-infested range. Liver concentrations of Cu decreased (r2 = .45; P < .02) as the percentage of bites consumed as locoweed increased, but concentrations after grazing locoweed-infested range were still within normal ranges. Changes in liver concentrations of other minerals were not related (P > .15) to consumption of locoweed. These data indicate that previous grazing history can have significant effects on liver mineral stores and that, under our conditions, consumption of locoweed by grazing beef steers altered liver Cu concentrations. Toxic effects of locoweed consumption would likely occur before Cu deficiency would be induced by grazing locoweed-infested range; hence, supplementation of Cu would seem unlikely to alter the course of locoweed toxicosis.     

Effects of nitric oxide synthase gene knockout on neurotransmitter release in vivo

Previous studies suggest that low bone mass is a complication of alcoholic liver disease. Nevertheless, little is known about bone mass and bone metabolism in viral cirrhosis. To evaluate the prevalence and magnitude of hepatic osteopenia in these patients, bone remodeling status, and its relationship with the severity of liver disease and serum levels of insulin-like growth factor I (IGF-I), we studied 32 consecutive patients with viral cirrhosis and no history of alcohol intake. Bone mineral density (BMD) was measured by dual x-ray absorptiometry in the lumbar spine (LS) and femoral neck (FN), and the values were expressed as the z score. Bone metabolism markers and hormone profiles were measured. Patients with viral cirrhosis showed reduced BMD in all sites (LS: -1.27 +/- 1.06, P < .001; FN: -0.48 +/- 0.96; P < .01). Of the 32 patients, 53% met the diagnostic criteria for osteoporosis. In patients, urine deoxypyridinoline (D-Pyr) as a marker of bone resorption and serum bone alkaline phosphatase (b-AP) as a marker of bone formation were significantly higher than in control subjects (P < .001 and P < .01, respectively). Serum IGF-I was lower than in control subjects (P < .001), and significant differences were also found between patients with and without osteoporosis (P < .05). BMD in LS correlated with severity of the disease, with serum levels of IGF-I, and with urine D-Pyr. Our findings show that viral cirrhosis is a major cause of osteoporosis in men, and that low serum IGF-I levels seem to play a role in the bone mass loss in these patients. The biochemical markers of bone remodeling suggest high-turnover osteoporosis in patients with viral cirrhosis.     

The (-)-enantiomer of gossypol inhibits proliferation of stromal cells derived from human breast adipose tissues by enhancing transforming growth factor beta1 production

BACKGROUND: Age-related osteoporosis may be associated with inefficient intestinal calcium absorption and bone remodeling. OBJECTIVE: We investigated the pathogenesis of age-related osteoporosis in Chinese women with habitual low calcium intakes. DESIGN: We studied the response of intestinal calcium absorption, calcitropic hormones, and biochemical bone markers to graded dietary calcium deprivation. RESULTS: The osteoporotic subjects (n = 25) had higher urinary calcium excretion (P < 0.05) and lower plasma 1,25-dihydroxyvitamin D concentrations (P < 0.02) than did age-matched control women (n = 25). Parathyroid hormone was not significantly different from that in age-matched control women but was significantly higher than in young women (n = 15, P < 0.05). Fractional 45Ca absorption was approximately 61% in all 3 groups when the diet was unmodified and increased to 71%, 69%, and 68% in the osteoporotic subjects, age-matched control women, and young women, respectively, when dietary calcium was reduced to 300 mg/d. When the osteoporotic women were calcium deprived, serum 1,25-dihydroxyvitamin D failed to increase but urinary calcium excretion persisted. In contrast, supplementation with 1200 mg Ca resulted in a lowering of parathyroid hormone (P < 0.005 compared with the unmodified diet) and 1,25-dihydroxyvitamin D (P < 0.01) and decreased fractional 45Ca absorption (P < 0.01), suggesting that the increased calcium intake was associated with a potent compensatory ability of the intestine and calcitropic hormones to adapt. Calcium supplementation lowered osteocalcin (P < 0.05) but not alkaline phosphatase, which remained elevated in the osteoporotic subjects at all stages. CONCLUSIONS: Elderly osteoporotic women had reduced 1,25-dihydroxyvitamin D production, excessive urinary calcium loss, and high bone turnover. The Chinese women had exceptionally potent intestinal calcium absorption.     

Apparent digestibility of a debranched amylopectin-lipid complex and resistant starch incorporated into enteral formulas fed to ileal-cannulated dogs1

The purpose of this study was to evaluate apparent digestibility in ileal-cannulated dogs fed enteral diets containing a debranched amylopectin-lipid complex (V-complex) or resistant starch. Six ileal-cannulated dogs were randomized into a replicated 3 x 3 Latin square design for determination of digestibility of three experimental treatments. Dietary treatments were as follows: 1) control; 2) V-complex; and 3) resistant starch. Diets were similar in chemical composition. Apparent digestibility of dry matter (DM), organic matter (OM) and carbohydrate by dogs fed the control diet was higher (P < 0.05) than for dogs consuming the other diets. Mean apparent digestibilities of carbohydrate for the control, V-complex and resistant starch diets were 89, 76 and 43%, respectively. Both DM and carbohydrate digestibility were lower (P < 0.05) for resistant starch compared with V-complex. Fecal dry and wet weights for dogs fed the control diet were lower (P < 0.05) than for those receiving either the resistant starch or V-complex treatments. Dogs fed the V-complex diet produced approximately 90 g less feces per day than dogs fed resistant starch. Dietary incorporation of V-complex to replace traditional carbohydrates may be beneficial for diabetic patients because of the decreased digestibility and subsequent glucose absorption rate. Furthermore, incorporation of resistant starch into enteral formulas may improve gastrointestinal tract health status as a result of increased fecal bulk, potential dilution of toxins in the intestinal lumen and greater production of short-chain fatty acids.