Search PubMed⌕ Search

Biomedical subjects

D H Baker

Publications and source records attributed to D H Baker.

At least 127 records · Page 7Linked to original sources
PubMed1992

Urinary taurine excretion as a function of taurine intake in adult cats.

Experiments were designed to develop a urinary excretion model for the study of taurine status in adult cats. The time course of changes in urinary taurine excretion in response to alterations in dietary taurine was examined in Experiment 1. Urinary taurine excretion decreased rapidly when cats were switched from a casein diet supplemented with 2000 mg crystalline taurine/kg diet to a diet containing no supplemental taurine reaching a plateau in 2 d, but the cats required 7 d to reach a plateau when switched from the nonsupplemented diet to the 2000 mg taurine/kg diet. In Experiment 2, the casein diets contained graded levels of crystalline taurine (0, 250, 500, 1000, 1500 or 2000 mg/kg). After a 7-d adjustment period, urinary taurine excretion was quantified over 5 d, and blood taurine concentrations were measured on d 6. Plasma taurine concentration increased linearly (r = 0.88) as taurine intake increased, but whole-blood taurine increased asymptotically. Taurine intakes of greater than 96 mumol/(kg body wt.d) resulted in urinary excretion rates that were 15 times greater than those occurring below this break point. We suggest that urinary taurine excretion by cats fed taurine at levels above the break point has potential for estimating taurine bioavailability in intact meat-source proteins.

Animals↗
PubMed1992

Efficiency of dietary methionine utilization by young pigs.

An assay was conducted to determine the efficiency of dietary methionine retention for protein accretion in 14-kg pigs. During an 18-d feeding period, pigs were fed a chemically defined amino acid basal diet [147.7 g protein (N x 6.25)/kg, 14.43 MJ metabolizable energy/kg, 4000 mg L-cystine/kg] containing 1150, 1725 or 2300 mg L-methionine/kg. Linear (P less than 0.01) responses in daily gain, daily food intake, daily methionine intake, gain:food ratio and empty body weight gain were obtained as dietary methionine level increased. Representative pigs were killed at the beginning of the assay for whole-body compositional analysis, and the comparative slaughter technique was used to estimate methionine retention. Absolute retention of methionine, protein, water, fat and ash increased linearly (P less than 0.05) with dietary methionine supplementation. Regressing methionine retained on methionine intake resulted in an efficiency of methionine retention above maintenance of 71.7%. The maintenance requirement for methionine was estimated to be 57 mg/d (8 mg/kg body wt 0.75) in the presence of excess dietary cystine. Concentrations of most indispensable amino acids, including methionine, in whole-body protein increased linearly, although glycine and proline concentrations decreased as dietary methionine level increased. This suggests that the ratio of whole-body collagen protein to non-collagen protein decreases as dietary methionine is incremented from deficiency to near adequacy.

Amino Acids↗
PubMed1992

Cellular antioxidant status and human immunodeficiency virus replication.

The factors that stimulate replication of the human immunodeficiency virus (HIV) and determine the period of disease latency are poorly understood. Recent evidence from in vitro cell culture studies of HIV-infected cells suggest that HIV activity is profoundly affected by the presence of antioxidants, such as glutathione and ascorbic acid, in the cell culture medium. These in vitro observations and reports of global glutathione deficiency in nonsymptomatic HIV-seropositive subjects suggest that cellular antioxidant status may be an important factor determining the latency period of HIV infection. The molecular mechanisms underlying HIV activation are beginning to be understood and point to a potentially important role for NK-kappa B, a cellular transcription factor that may be modulated by cellular antioxidant status.

Acetylcysteine↗
PubMed1992

Ideal amino acid pattern for 10-kilogram pigs.

Two growth assays and one nitrogen balance experiment were conducted to develop an ideal amino acid pattern for 10-kg pigs. Crossbred pigs were fed chemically defined amino acid diets containing four indispensable amino acid (AA) patterns: 1) the Illinois final amino acid pattern (IFP), a recently developed AA profile for purified diets; 2) the Illinois ideal amino acid pattern (IIP), a modification of IFP; 3) the Wang and Fuller ideal amino acid pattern (WFIP); and 4) the 1988 National Research Council (NRC) amino acid requirement pattern for 10-kg pigs (NRCP). A mixture of dispensable AA consisting of glutamate, glycine, and proline that had been proven to be an efficient mixture of dispensable AA nitrogen was fed together with the indispensable AA patterns. Diets were made isonitrogenous and isoenergetic within experiments. In Exp. 1, pigs were given ad libitum access to experimental diets with AA levels set above the NRC AA requirements. Regardless of which AA pattern was fed, pigs had similar (P greater than .05) daily gains, daily feed intakes, and gain:feed ratios. In Exp. 2, all levels of indispensable and dispensable AA were reduced to 50% of levels present in Exp. 1. When pigs had ad libitum access to these diets, daily gains of pigs fed IIP were superior (P greater than .05) to those of pigs fed IFP or NRCP, but similar (P greater than .05) weight gains occurred in pigs fed IFP, WFIP, and NRCP. In Exp. 3, the efficiency of nitrogen utilization of the four indispensable AA patterns was evaluated by a nitrogen balance experiment in pigs equally fed the same experimental diets fed in Exp. 2. Pigs fed NRCP utilized nitrogen with an efficiency of 74%, which was less (P less than .001) than the efficiencies of 79 to 80% obtained in pigs fed IFP, IIP, and WFIP. Nitrogen retained (grams) per gram of nitrogen intake from indispensable AA was greater (P less than .01) for IIP than for either IFP or WFIP. The results of these experiments indicate that WFIP contains excesses of leucine, valine, phenylalanine plus tyrosine, methionine plus cystine, and threonine for pigs between 10 and 20 kg BW. Also, NRCP is probably first-limiting in leucine and also limiting in other AA, resulting in lower nitrogen utilization than IIP. The pattern of indispensable AA in IIP (grams of AA/100 g lysine) is as follows: lysine (100), methionine+cystine (60), threonine (65), tryptophan (18), phenylalanine+tyrosine (95), leucine (100), isoleucine (60), valine (68), arginine (42), and histidine (32).

Amino Acids↗
PubMed1992

Methodology for assessing zinc bioavailability: efficacy estimates for zinc-methionine, zinc sulfate, and zinc oxide.

The bioavailability of zinc-methionine (ZnMET) was compared to that of feed-grade ZnSO4.H2O using three different diets: purified (crystalline amino acid [AA]), semipurified (soy isolate), and complex (corn-soybean [C-SBM]) diet. With the Zn-deficient purified or semipurified diet, weight gain and tibia Zn responded linearly to both ZnSO4.H2O and ZnMET supplementation. Common-intercept, multiple linear regression indicated differences in Zn bioavailability between ZnMET and ZnSO4.H2O for both diets as indicated by bone Zn. With the ZnSO4.H2O standard set at 100%, bioavailability of Zn from ZnMET was 117% (P less than .05) in the AA diet and 177% (P less than .01) in the soy isolate diet. The ZnMET was also compared to ZnSO4.H2O in a C-SBM diet containing 117 mg of Zn/kg. When high levels of Zn were added to this diet (0, 250, 500, and 750 mg/kg of supplemental Zn), consistent tissue Zn responses did not occur beyond the first increment. Addition of lower levels of supplemental Zn (0, 5, 10, 20, 30, 40 and 50 mg/kg) to a Zn-unsupplemented C-SBM basal diet (45 mg/kg of Zn), however, resulted in a broken-line, two-slope response in tibia Zn for both ZnMET and ZnSO4.H2O. Inflection points occurred at 60 and 54 mg of Zn/kg of diet for ZnSO4.H2O and ZnMET, respectively. The ratio of slopes (ZnMET:ZnSO4.H2O) below the inflection points was 206% (P less than .01), indicating that Zn was considerably more bioavailable in ZnMET than in ZnSO4.H2O for chicks consuming C-SBM diets. When feed-grade ZnO was compared to feed-grade ZnSO4.H2O in chicks consuming C-SBM diets, bone Zn slopes below the respective inflection points indicated that Zn was 61% bioavailable in ZnO relative to ZnSO4.H2O.

Animal Feed↗
PubMed1992

Apparent and true amino acid digestibility of a crystalline amino acid mixture and of casein: comparison of values obtained with ileal-cannulated pigs and cecectomized cockerels.

Six ileal-cannulated pigs that averaged 100 kg BW and 16 adult cecectomized cockerels that averaged 2.35 kg BW were used to determine apparent and true digestibilities of amino acids (AA) in a complete crystalline AA mixture and in casein. A protein-free (PF) diet was included as a treatment to estimate endogenous AA losses. Fasted cockerels were compared to cockerels fed PF diets for calculation of true digestibility of AA in cockerels. For the AA diet, true digestibility of indispensable AA in the pig ranged from a low of 97.2% for leucine to a high of 100.5% for arginine (Arg). True digestibility of indispensable AA in casein ranged from a low of 93.5% for isoleucine (Ile) to a high of 99.9% for Arg. Correcting for endogenous losses increased digestibilities of lysine (Lys) and threonine (Thr) in pigs fed the AA diet by 2.4 and 7.1%, respectively, and increased Lys and Thr digestibility in pigs fed the casein diet by 1.8 and 6.1%, respectively. Feeding a PF diet to chickens to correct for endogenous losses resulted in higher true digestibility values for all AA with the exception of tryptophan, methionine, and Arg than those obtained using fasted animals. True digestibilities of Thr were 88.3 and 86.6% for AA and casein diets, respectively, using fasted controls but were 97.5 and 94.5% when the PF control was used. Proline digestibility was increased (P < .05) substantially in both pigs and cockerels when the PF control was used to correct for endogenous AA losses. Regardless of species, Ile in casein had a lower true digestibility value than any other indispensable AA. The results of this study indicated that true digestibilities of AA in a mixture of crystalline AA and in casein are essentially 100% in both pigs and cockerels.

Amino Acids↗
PubMed1992

Maximal portion of the young pig's sulfur amino acid requirement that can be furnished by cystine.

Three pig experiments were conducted using a chemically defined, amino acid diet under conditions in which all nutrients were 100% bioavailable to assess the maximal portion of the sulfur amino acid (SAA) requirement that could be furnished by cystine (Cys). In Exp. 1, a methionine (Met)-deficient diet containing .12% L-Met and .40% L-Cys was supplemented with graded levels of L-Met. Pigs weighing 10 kg initially responded quadratically (P less than .05) to Met supplementation. A two-slope, broken-line regression model (weight gain regressed on percentage of dietary Met) estimated an infection point at .23% dietary Met. A constant level of .46% dietary SAA with differing Met:Cys weight (wt:wt) ratios was used in Exp. 2. Pigs fed Met:Cys ratios of 60:40 and 50:50 had similar (P greater than .05) weight gains, but pigs fed a 40:60 Met:Cys ratio gained less (P less than .05) than those fed the other diets. Maintaining dietary sulfur at .111% in Exp. 3, pigs fed Met:Cys ratios (wt:wt) of 100:0, 55:45, 50:50, and 45:55 gained weight at similar (P greater than .05) rates, but pigs fed the 45:55 Met:Cys ratio had a tendency to produce lower weight gains. Regardless of whether a constant dietary SAA or sulfur level was maintained, no more than 50% of the young pig's total SAA requirement (wt:wt) could be furnished by Cys.

Amino Acids, Sulfur↗
PubMed1992

Methionine requirement of pigs between 5 and 20 kilograms body weight.

Four nursery experiments were conducted using a methionine (Met)-deficient feather meal-corn-soybean meal-dried whey basal diet (20% CP; 3,250 kcal of ME/kg, .11% choline, .19% Met, 1.00% cystine) supplemented with lysine, tryptophan, and histidine to determine the Met requirement of 5- to 10- and 10- to 20-kg pigs. Based on a true Met digestibility value of 81.6% estimated by a pig ileal digestibility assay, the Met-deficient basal diet contained .155% of digestible Met. A preliminary experiment (Exp. 1) indicated that pigs fed the Met-deficient basal diet when fortified adequately with Met could produce weight gains similar to those of pigs fed a 20% CP practical corn-soybean meal-dried whey diet. In Exp. 2 and 3, crossbred pigs weighing 5.8 kg initially were fed diets containing graded levels of digestible Met between .195 and .355%. Average daily gain increased quadratically (P less than .05) as the level of Met increased. When the data of Exp. 2 and 3 were examined together, the digestible Met requirement of 5- to 10-kg pigs was estimated to be .255% of the diet. In Exp. 4 and 5, crossbred pigs averaging 10 kg were fed digestible Met concentrations ranging from .155 to .315%. Average daily gain increased quadratically (P less than .05). The digestible Met requirement of 10- to 20-kg pigs was estimated at .255% for maximal weight gain, which was similar to that of 5- to 10-kg pigs. Assuming an 89% digestibility of Met in practical corn-soybean meal diets, the total Met level needed in practice would be .29%.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acids, Sulfur↗
PubMed1992

Amino acid fortification of a low-protein corn and soybean meal diet for chicks.

Seven experiments were conducted to investigate whether a 19% CP corn and soybean meal (CS) diet could be fortified properly with amino acids (AA) to produce performance in 1- to 3-wk-old chicks equal to that obtained with a 23% CP, CS diet supplemented with Met. In one experiment, the assay was carried out to 6 wk of age. During 4- to 6-wk posthatching, the positive control was a 20% CP, CS diet with added Met and the low-protein diet was a 16% CP, CS diet fortified with limiting AA. The two most limiting AA in the low-protein diet (19% CP) were found to be Met and Lys. Arginine, Val, and Thr were observed to be limiting as well. Weight gain and feed efficiency were substantially increased and body fat content decreased when the low-protein diet was supplemented with the five limiting AA and amino nitrogen in the form of Glu. Addition of potassium had no effect on performance of chicks fed the AA-fortified, low-protein diet. With all trials considered together, chicks fed the low-protein diet fortified with the five limiting AA and Glu gained at the same rate with similar feed efficiency and had estimated body fat levels comparable to birds fed the 23% CP, positive control diet. From 3 to 6 wk of age, chicks fed the AA-fortified, 16% CP diet had growth performance similar to chicks fed the 20% CP, positive control diet.

Adipose Tissue↗
PubMed1991

Effect of fiber, protein source and time of feeding on methotrexate toxicity in rats.

Several rat experiments were conducted to determine effects of fiber and alternate protein sources on methotrexate (MTX) toxicity associated with a casein-based semipurified diet. Additional experiments were conducted to determine the critical time of feeding in relation to toxicity development. Rats adapted to a casein-based semipurified diet developed severe anorexia and diarrhea on d 3 and 4 post-MTX dosing. Addition of amorphous cellulose to the semipurified casein-based diet slightly reduced toxicity symptoms. Additions of crystalline cellulose, hemicellulose and pectin did not lessen toxicity symptoms. Replacing casein with soybean concentrate totally alleviated the toxicity symptoms. Toxicity was lower when 25% of the protein normally supplied by casein was replaced with soybean concentrate, and no toxicity symptoms were present when 50% or more of the protein was provided by soybean concentrate. Replacing casein with whey isolate or hamburger had no effect on toxicity; replacing casein with egg albumen or corn gluten meal lessened toxicity symptoms but did not totally alleviate them. Feeding the casein-based diet only 1 d before and 1 d after MTX injection resulted in toxicity. However, feeding the same diet only after MTX injection did not cause toxicity. Results indicate that fiber sources have little effect on MTX toxicity, but replacing casein with soybean concentrate completely alleviates toxicity symptoms. Time of feeding affects subsequent development of toxicity.

Animals↗
PubMed1991

Effect of soy products on methotrexate toxicity in rats.

Several experiments were conducted to determine the effect of various soy products on methotrexate (MTX) toxicity. Products tested included soybean meal, soybean concentrate, soybean isolate and soybean fiber, which were provided as replacements for casein or cornstarch in a semipurified diet. Soybean meal and soybean concentrate offered the greatest protection, completely alleviating MTX-induced anorexia and diarrhea when included as the sole protein source and fed 14 d prior to and 7 d following intraperitoneal MTX injection at 20 mg/kg body weight. Positive responses also were observed with soybean isolate and soybean fiber. Histological examination of the small intestine of MTX-injected animals revealed that soybean concentrate and soybean isolate prevented the necrosis observed in animals fed the casein-based semipurified diet. Methotrexate levels in plasma were similar for animals fed semipurified diets in which protein was supplied by casein, soybean concentrate or soybean isolate. Thus, altered plasma MTX levels did not explain the differences among protein sources in ameliorating MTX-induced anorexia and gut toxicity. White blood cell counts were depressed by MTX in animals fed all diets.

Animals↗
PubMed1991

Phosphorus, but not calcium, affects manganese absorption and turnover in chicks.

Two balance studies with growing chicks were conducted to evaluate the effects of excess Ca or excess P on endogenous fecal Mn excretion and true Mn absorption. An isotope-dilution technique was used to estimate endogenous manganese in excreta. Supplements were added to a corn-soybean diet containing 1% Ca, 0.7% P (0.5% available P) and 37 mg Mn/kg. In Experiment 1, supplemental Ca levels of 0, 0.5 and 1.0% from feedgrade limestone were compared. True absorption of Mn was not affected by Ca level (P greater than 0.10) and averaged 2.8% for birds fed the Mn-unsupplemented diet. In Experiment 2, a 2 x 3 factorial arrangement of treatments included: 100 and 1000 mg/kg supplemental Mn (from MnSO4.H2O) and 0, 0.4 and 0.8% added P supplied by dicalcium phosphate. Excess P significantly decreased true absorption of Mn (P less than 0.01). In birds fed 100 mg/kg supplemental Mn, absorption of Mn decreased 22% as excess P increased from 0 to 0.8%, whereas in birds fed 1000 mg/kg supplemental Mn, Mn absorption decreased 59% as a result of 0.8% P supplementation. These results confirm that the antagonism of Mn by inorganic P is due to reduced gut absorption of Mn.

Animals↗
PubMed1991

Manganese turnover in chicks as affected by excess phosphorus consumption.

A repletion-depletion assay was conducted to evaluate the effect of Mn status and excess dietary P provided as dicalcium phosphate on Mn excretion and turnover. Chicks were fed either Mn-adequate (30 mg Mn/kg) or high Mn (1000 mg Mn/kg) casein-dextrose diets for 7 d. Following this loading period, the chicks were fed a Mn-deficient casein-dextrose diet (1.4 mg Mn/kg) with or without 0.5% excess P supplied from dicalcium phosphate. Whole body (without feathers) and selected body tissues (liver, kidney, gut, tibia and feathers) were assayed for Mn content at 0, 0.5, 1, 1.5, 2, 2.5, 3, 4, 6, 8, 10, 15 and 20 d after initiation of the Mn-deficient diet. Excess P had little effect on Mn turnover. All tissues showed significantly reduced biological half-lives (P less than 0.05) as a result of loading chicks with a high level of Mn (1000 mg/kg) during the 7-d loading period. However, there was wide variation in Mn turnover rates among tissues. Liver, kidney and whole body contained readily exchangeable manganese in much higher proportions than did bone.

Animals↗
PubMed1991

A chemically defined diet for maximal growth of pigs.

Three growth assays and one balance experiment were conducted to determine the optimal mixture of dietary amino acids for 10-kg pigs fed a chemically defined diet. Pigs were meal fed at 0700 and 1700 h in all experiments. Increasing all indispensable amino acids by 20% from their original levels improved weight gain and gain:feed ratio to levels equivalent to those of pigs fed a 20% protein corn-soybean meal-dried whey positive control diet. Replacing the glutamate-glycine-proline dispensable amino acid mixture with a complete mixture of dispensable amino acids (i.e., glutamate, glycine, proline, glutamine, serine, alanine, aspartate and asparagine) did not improve growth rate. A balance study showed that retention of nitrogen and energy (percentage of intake) from the final purified diet was superior to that of pigs fed the corn-soybean meal-dried whey diet. Metabolizable energy and metabolizable energy corrected for nitrogen retention of the final purified amino acid diet were determined to be 14.43 and 13.96 MJ/kg diet, respectively. The chemically defined diet developed here for young pigs provides a means of studying nutrient utilization in the pig under conditions in which all nutrients are essentially 100% bioavailable.

Amino Acids↗
PubMed1991

Toxicity and tissue accumulation of copper in chicks fed casein and soy-based diets.

Experiments were conducted to study Cu toxicity in chicks fed casein or soy-containing diets containing graded levels of excess CuSO4.5H2O. Differences between diets in measures of Cu toxicity were pronounced. Addition of 800 mg of Cu/kg to a casein-dextrose semipurified diet decreased weight gains by 63%, but the same addition of Cu to a corn-soybean meal complex diet decreased gains by only 8%. At all levels of Cu supplementation (100, 200, 400 or 800 mg/kg), Cu deposition in the liver was increased markedly in chicks fed casein diets compared with those fed the complex diet. Substituting soy-protein concentrate for casein in the semipurified diet resulted in a marked decrease in Cu toxicity as measured by weight gain reductions and tissue accumulation of Cu.

Animals↗
PubMed1991

Soybean protein solubility in potassium hydroxide: an in vitro test of in vivo protein quality.

Experiments were conducted to assess protein solubility in .2% KOH as an indicator of soybean protein quality for chicks and pigs and to assess effects of particle size on protein solubility. As the particle size (micron) of soybean meal (SBM) increased, protein solubility (%) decreased (b = -.0206). In two 9-d chick trials, dehulled SBM (48% CP) was subjected to various autoclaving times and then fed as the sole source of dietary protein to young chicks. Increasing autoclaving times from 0 to 40 min at 120 degrees C resulted in a quadratic decrease in protein solubility. A broken-line model was fitted wherein gain:feed of chicks was plotted as a function of protein solubility. The analysis showed no reduction in feed efficiency with solubilities greater than 59 +/- 1.5% (mean +/- SEM). When solubility was below 59%, however, gain:feed decreased 1.5% for each 1% decrease in protein solubility. The third trial (13 d) was conducted with 7.5-kg pigs fed autoclaved SBM (44% CP) as the primary source of protein. Feed efficiency was significantly decreased when protein solubility was less than 66%. This study showed that protein solubility in KOH was a good index of in vivo soybean protein quality, and that it is important to standardize SBM particle size when applying the KOH assay.

Animal Feed↗
PubMed1991

Safety of L-tryptophan for pigs.

Epidemic eosinophilia-myalgia syndrome (EMS) associated with excess L-tryptophan (Trp) consumption in humans has been declared a major public health problem. The EMS problem has not been observed in pigs, nor has comprehensive pathology associated with EMS in humans been described. Experiments were therefore conducted to evaluate the pathology and effects of excess dietary L-Trp for finishing (79 to 119 kg) pigs and to determine an LD50 of Trp for pigs. In Exp. 1, addition of .1 or 1% Trp to corn-soybean meal diets had no effect on growth performance or leukocyte and relative eosinophil counts or on plasma aspartate transferase, creatine phosphokinase, and lactate dehydrogenase activities. Likewise, untoward pathological effects of Trp feeding were not observed in the animals under study. In Exp. 2, supplementing the basal diet with 0, 2, and 4% Trp caused linear (P less than .05) decreases in weight gain, feed intake, and gain:feed ratio. Mortality could not be produced by acute oral dosing in the LD50 study (Exp. 3), wherein Trp doses between 2.00 and 5.71 g/kg of BW were administered by stomach tube. Vomiting occurred at oral doses greater than 5.71 g/kg of BW. These results suggest that oral ingestion of Trp in pigs is safe and that pigs can tolerate considerable excesses of Trp.

Administration, Oral↗