Biomedical subjects

D H Baker

Publications and source records attributed to D H Baker.

At least 37 records · Page 2Linked to original sources

PubMed2002

Ideal ratio (relative to lysine) of tryptophan, threonine, isoleucine, and valine for chicks during the second and third weeks posthatch.

Six bioassays were conducted to determine the ideal ratios of several amino acids relative to Lys. Young male crossbred chicks were fed diets based on corn gluten meal and synthetic amino acids that could be made singly deficient in Lys, Trp, Thr, Ile, or Val. Diets for all assays contained 3,400 kcal ME/kg, and L-glutamic acid was used to make all diets (within and among assays) equal in crude protein at 22.5% of the diet. True digestibility assessment of corn gluten meal in cecectomized roosters facilitated dose-titration studies so that least squares fitted one-slope broken-lines and quadratic regression equations could be calculated to establish inflection points for weight gain and gain:feed. Four battery pens of four chicks were fed one of six amino acid levels from 8 to 21 or 22 d posthatching. Weight gain and gain:feed responded quadratically (P < 0.01) to increasing doses of digestible Lys (0.68 to 1.28%), Trp (0.09 to 0.24%), Thr (0.41 to 0.81%), Ile (0.45 to 0.95%), and Val (0.51 to 1.06%). Broken-line least squares analysis predicted breakpoints for gain and gain:feed, respectively, of: Lys (0.85, 0.96%), Trp (0.16, 0.16%), Thr (0.53, 0.53%), Ile (0.59, 0.58%), and Val (0.74, 0.74%). The intercept of the quadratic regression curve and the plateau of the broken line predicted digestible Lys requirements for gain and gain:feed, respectively, of 0.95 and 1.03%. Similar calculations predicted digestible Trp requirements of 0.18% for gain and gain:feed, digestible Thr requirements of 0.59% for gain and 0.60% for gain:feed, digestible Ile requirements of 0.68% for gain and gain:feed, and digestible Val requirements of 0.81% for gain and 0.82% for gain:feed. Regardless of curve-fitting method, gain:feed requirements for Lys were much higher than weight gain requirements. Using the higher of the broken-line requirement estimates for gain and gain:feed, ideal ratios (% of Lys) were as follows: Lys (100), Trp (16.6), Thr (55.7), Ile (61.4), and Val (77.5).

Amino Acids, Essential↗

PubMed2002

Growth performance and whole-body composition of pigs experimentally infected with Mycoplasma hyopneumoniae.

Mycoplasma hyopneumoniae (Mh) is the primary infectious pathogen responsible for enzootic pneumonia in pigs. Although Mh is thought to impair growth performance, whole-body composition, and fat and protein accretion in pigs with pneumonia have not been reported and the mechanism through which Mh reduces growth is unknown. The objectives of this study were to evaluate the effects of Mh on growth performance, whole-body composition, and protein and fat accretion in nursery pigs and to determine whether Mh infection increases the expression of interleukin (IL)-1beta, IL-6, and tumor necrosis factor-alpha (TNF-alpha). Sixty-four 2-wk-old Mh-free pigs were used (two trials) in a randomized complete block design. In each trial, two pigs were housed in each of 16 disease-containment chambers. At 4 wk of age, pigs were inoculated intratracheally with 3 mL of Mh broth (P5722-3, 10(7) cfu/mL) or sterile Friis culture medium. Clinical signs of disease and feed intake were monitored daily and body weight was determined weekly for 4 wk. Whole-body composition was determined from pigs killed 0, 14, and 28 d after inoculation, and the comparative slaughter technique was used to estimate protein and fat accretion. At death, gross lung lesions were quantified, and lung tissue was collected to verify the presence or absence of Mh, and to determine cytokine mRNA levels. Control pigs displayed no overt signs of infection and were Mh-negative and free of pulmonary lesions. Pigs inoculated with Mh showed pneumonic coughing (P < 0.005), were Mh-positive, and had pulmonary lesions that affected 4.5% (P < 0.01) and 14.1% (P < 0.001) of total lung surface area at 14 and 28 d, respectively, after inoculation. Ribonuclease protection assays revealed increased IL-1beta (P < 0.04) and TNF-alpha (P < 0.06) mRNA in lung tissue collected from a lesion site compared with tissue collected 10 cm from a lesion site or from control pigs. Interestingly, Mh did not depress weight gain or feed efficiency during any week of the 28-d study (P > 0.10). Moreover, Mh did not affect whole-body fat or protein accretion (P > 0.10). Thus, in spite of inducing disease and expression of inflammatory cytokines, Mh alone did not affect growth performance and whole-body composition of nursery pigs during the 4-wk experiment. The ability of pigs to contend with Mh may have resulted from the absence of other pathogens that generally co-exist with Mh under commercial conditions.

Animals↗

PubMed2001

Microbial phytase does not improve protein-amino acid utilization in soybean meal fed to young chickens.

Three growth trials were conducted with young chicks to evaluate crude protein (CP) utilization in soybean meal (SBM) as affected by dietary addition of microbial phytase. In assay 1, chicks were fed two CP-deficient (50 or 150 g CP/kg) levels of dehulled SBM, and each SBM level was then supplemented with equimolar amounts of cystine or methionine (Met) or with 1200 U phytase/kg. At 50 g CP/kg, cystine or Met supplementation improved (P < 0.05) measures of growth performance, but when 150 g CP/kg from SBM was fed, only Met addition improved (P < 0.05) weight gain, food efficiency and protein efficiency ratio (PER). Thus, Cys was more limiting than Met in the diet that contained 50 g CP/kg, but Met was clearly first-limiting in the diet that contained 150 g CP/kg. Phytase supplementation did not improve (P > 0.10) chick performance at either level of CP. Chicks in assay 2 were fed 100 g CP/kg furnished by SBM, casein or corn gluten meal in the absence and presence of 1200 U phytase/kg. Weight gain, gain/food and PER values were greater (P < 0.05) in chicks fed SBM than in those fed casein, and greater (P < 0.05) in chicks fed casein than in those fed corn gluten meal. Phytase supplementation had no effect (P > 0.10) on any measure of chick performance, regardless of the protein source fed. In assay 3, three deficient levels of CP (50, 100 and 150 g/kg) from SBM were fed in the absence and presence of 1200 U dietary phytase/kg. Weight gain, food efficiency and protein accretion increased linearly (P < 0.05) as a function of protein intake, but phytase supplementation had no effect (P > 0.10) on slopes of the body weight and protein accretion curves. Likewise, phytase addition did not affect (P > 0.10) measures of protein utilization, i.e., weight gain/protein intake and protein gain/protein intake at any of the CP levels that were fed. Because sulfur amino acids are the growth-limiting factors when protein-deficient levels of SBM are fed to young chicks, we conclude that dietary addition of phytase does not improve sulfur amino acid utilization in SBM.

6-Phytase↗

PubMed2001

Zinc bioavailability in tetrabasic zinc chloride and the dietary zinc requirement of young chicks fed a soy concentrate diet.

Three chick assays were conducted to determine a bioavailable Zn requirement and to establish a Zn relative bioavailability (RBV) value for tetrabasic Zn chloride [TBZC, i.e., Zn5Cl2(OH)8]. In Assay 1, 8-d-old chicks were fed a Zn-deficient soy concentrate diet (8.8 mg/kg bioavailable Zn) supplemented with 0, 5.81, 10.81, 15.10, and 20.25 mg Zn/kg from ZnSO4.7H2O for 14 d to establish a linear response range and estimate a bioavailable Zn requirement. Weight gain of chicks increased linearly (P < 0.01; r2 = 0.99) when the first three levels of Zn were fed. Broken-line analysis of the weight gain data indicated a bioavailable Zn requirement of 22.4 mg/kg. In Assay 2, RBV of Zn in TBZC was determined by multiple-linear regression slope-ratio methodology. The Zn-deficient basal diet was supplemented with 0, 5.81, and 10.81 mg Zn/kg from ZnSO4.7H2O to produce a linear growth response as determined in Assay 1. The same basal diet was supplemented with 5.38 and 10.81 mg Zn/kg from TBZC. The RBV of Zn in TBZC was found to be 102%, which was not different (P > 0.10) from 100%. A third assay was conducted as described for Assay 2, and the RBV of Zn in TBZC was 111%, which was not different from 100%. In summary, the RBV of Zn in TBZC was not different from that of ZnSO4.7H2O, and the minimal bioavailable Zn requirement for chicks 1 to 3 wk of age fed a soy concentrate diet was estimated at 22.4 mg/kg.

Animal Feed↗

PubMed2001

Efficacy of phytase for increasing protein efficiency ratio values of feed ingredients.

Data previously reported in several studies have suggested that phytase improves amino acid digestibility in chicks. It was the objective of the current study to determine if phytase would increase the protein efficiency ratio (PER) values (g weight gain per g protein intake) for several feed ingredients fed to chicks. Six experiments were conducted and ingredients evaluated were casein, soybean meal, canola meal, cottonseed meal, peanut meal, wheat middlings, wheat bran, rice bran, defatted rice bran, meat and bone meal, and corn gluten meal. Casein was evaluated to serve as a phytate-free control ingredient. Each feedstuff was analyzed for CP and included in cornstarch:dextrose diets as the only source of protein to provide 10% dietary protein in Experiments 1 to 5 or 18% dietary protein (soybean meal) in Experiment 6. Dietary Ca and nonphytate P levels were varied among experiments and ranged from 0.95 to 1.5% Ca and 0.35 to 0.675% nonphytate P. The test ingredient diets were fed with 0 or 1,200 units of phytase/kg to New Hampshire x Columbian chicks from 8 to 17 or 20 d of age. The PER values varied greatly among ingredients, ranging from 1.4 for corn gluten meal to 4.2 for canola meal. Phytase addition had no significant effect (P > 0.10) on PER values for any of the ingredients evaluated, except for an increase for casein in one experiment. The results indicated that 1,200 U of phytase/kg did not significantly increase protein utilization of several feed ingredients as assessed by a PER chick growth assay.

6-Phytase↗

PubMed2001

The effect of citric acid on the calcium and phosphorus requirements of chicks fed corn-soybean meal diets.

Data previously reported from our laboratory indicated that supplementation of a corn-soybean meal diet with citric acid improves P utilization in chicks. The four experiments reported herein were conducted to further evaluate the effects of citric acid on Ca and P utilization for chicks fed a corn-soybean meal diet. Diets in all experiments were fed to chicks from 8 to 21 or 22 d of age. The first experiment evaluated the effect of 6% citric acid on the Ca requirement of chicks. A Ca-deficient basal diet [23% CP, 0.54% Ca, 0.45% available P (AP)] containing 0 to 0.7% supplemental Ca in 0.1% increments was fed with or without 6% citric acid. The results indicated that citric acid did not significantly affect the Ca requirement. A second experiment evaluated different levels of citric acid (0, 2, 4, or 6%) on P utilization, and results indicated that 4 and 6% citric acid produced the largest responses in growth and tibia ash. Experiments 3 and 4 were then conducted to determine whether 4 or 6% citric acid would reduce the level of supplemental P required. Dietary treatments were a P-deficient basal diet (23% CP, 1.0 or 1.3% Ca, 0.20% AP) supplemented with 0 to 0.25% inorganic P with or without 4 or 6% citric acid. When diets contained citric acid, weight gain and tibia ash were maximized at lower AP levels than when diets contained no citric acid. The results of this study indicate that citric acid increases P utilization in corn-soybean meal diets and reduces the AP requirement by approximately 0.10% of the diet.

Animal Feed↗

PubMed2001

True ileal digestibility of amino acids in sow's milk for 17-day-old pigs.

The digestibility of amino acids in sow's milk consumed by young pigs is currently unknown because of difficulties associated with collecting an adequate quantity of milk, and also problems in cannulating suckling pigs. A total of 14 kg of sow's milk was collected, two soluble indigestible markers (Co-EDTA and YbC13) were added, and the milk was fed to four pigs at 17 d of age that were fitted with a simple T-cannula at the terminal ileum. Another four cannulated pigs were offered a similar amount of a 20% DM liquid diet based on enzymatically hydrolyzed casein and lactose to assess endogenous amino acid losses. All pigs were fed about 875 g of each diet per day in 10 hourly meals from 0700 to 1700. Following 2 d of adaptation, ileal digesta were collected from 0800 to 1800 for 2 d. Diets and digesta were analyzed for amino acids using appropriate hydrolysis and preoxidation procedures. Average nitrogen true digestibility was 88%, whereas amino acid true digestibilities ranged from 84% (cystine and threonine) to 100% (methionine, histidine, and glutamic acid); the average for all amino acids was 92 +/- 4%. Based on average values, true digestibility of essential amino acids was not different from that of nonessential amino acids (P > 0.10). In whole milk, amino acids found in abundance in whey proteins (i.e., cystine, glycine, and threonine) were less (P < 0.05) digestible than amino acids predominating in casein proteins (i.e., glutamic acid, proline, and methionine). When true ileal digestible amino acid concentrations in sow's milk were expressed as ratios to digestible lysine, it appeared that threonine, tryptophan, and arginine were lower than what might be considered optimal. In conclusion, amino acids in sow's milk were highly digestible, but most of the amino acids had true ileal digestibility values significantly less than 100%.

Amino Acids↗

PubMed2001

Valine requirement of nursery pigs.

Six experiments were conducted to determine the true digestible valine requirement of 5- to 20-kg pigs. In Exp. 1, a valine-deficient diet for 5- to 10-kg pigs was developed and validated in terms of growth performance in response to supplemental L-valine. A different basal diet was validated for 10- to 20-kg pigs in Exp. 2. Both diets were demonstrated to be deficient in valine and to support performance equivalent to typical nursery diets when fortified with L-valine. In Exp. 3, true ileal digestibility of valine in the two basal diets was determined in eight pigs fitted with a simple T-cannula at the terminal ileum. Another four pigs received an enzymatically hydrolyzed casein-based diet to determine endogenous contributions to collected ileal digesta. The two diets were found to have true valine digestibilities of 82% (5- to 10-kg pigs) and 86% (10- to 20-kg pigs). In Exp. 4, 80 weaned pigs (5.8 kg) were offered the basal diet fortified with five incremental doses (0.08%) of L-valine. Weight gain increased quadratically (P < 0.05) with increasing levels of valine. Broken-line analysis revealed a true digestible valine requirement of 0.86 +/- 0.03%. In Exp. 5, the true digestible valine requirement of 10- to 20-kg pigs was estimated with 120 pigs (10.9 kg) using the second basal diet fortified with six incremental doses (0.05%) of L-valine. The data suggested a digestible valine requirement level of about 0.775%, which was reevaluated in Exp. 6, wherein pigs did not respond to levels of digestible valine higher than 0.775%. In conclusion, requirement estimates were 2.50 and 2.22 g of true digestible valine per megacalorie of ME for 5- to 10- and 10- to 20-kg pigs, respectively. These empirical estimates are in close agreement with recent estimates of the National Research Council Subcommittee on Swine Nutrition of 2.48 and 2.11 g of true digestible valine per megacalorie of ME, respectively.

Animal Nutritional Physiological Phenomena↗

PubMed2001

Dynamic ideal protein and limiting amino acids for lactating sows: the impact of amino acid mobilization.

The limiting amino acids for lactating sows were determined using 28 primiparous sows that were intentionally underfed both energy and protein during a 21-d lactation. Groups of four sows were allotted to litter-size treatments of 6, 7, 8, 9, 10, 11, or 12 by cross-fostering as needed within 48 h postpartum. Sows were killed on d 21 of lactation. The carcass, liver, gastrointestinal tract, reproductive tract, mammary gland, and other viscera were separated, weighed, ground, and analyzed for dry matter, crude protein, and amino acids. Simple linear equations were obtained for each amino acid within tissues as a function of litter size. The mobilization of amino acids from carcass, liver, gastrointestinal tract, reproductive tract, and other viscera increased as litter size increased. Amino acids were accreted to mammary glands as litter size increased (2.65 g lysine/21 d for each one-pig increase in litter size). Milk production needs were estimated (49.9 g lysine/21 d for each one-pig increase in litter size). The quantity of each amino acid required additionally as litter size increased was obtained from the difference between amino acid needs for milk production and mammary gland growth and those provided from tissue mobilization. The relative ratio among amino acids that are required additionally (ideal amino acid pattern) was compared with the relative ratio of amino acids that can be provided from a corn-soybean meal lactation diet. From the comparison, it was shown that threonine and lysine are the first-limiting amino acids, followed by valine, when tissue mobilization occurs during lactation. Lysine is the first-limiting amino acid, and valine becomes second-limiting followed by threonine, when sows do not mobilize body tissues during lactation. Thus, the limiting order of essential amino acids changes depending on feed intake and tissue mobilization of sows during lactation. Proper feeding of lactating sows should consider the expected degree of tissue mobilization during lactation.

Amino Acids↗

PubMed2000

Protein and body weight accretion of chicks on diets with widely varying contents of soyabean meal supplemented or unsupplemented with its limiting amino acids.

1. Two studies were conducted to evaluate the effects of relative deficiencies of methionine and threonine on the growth performance of 8- to 21-d-old chicks fed on isoenergetic diets containing a wide range of crude protein (CP) concentrations from dehulled soyabean meal (SBM). 2. Chicks fed on graded levels of SBM containing supplemental methionine and threonine (BAL) accreted whole-body protein more efficiently (P < 0.05) than those receiving graded levels of unsupplemented SBM (DEF), and superior (P < 0.05) growth performance was also obtained at lower CP levels when chicks were fed on the BAL diets. 3. Voluntary food intake increased between 30 and 220 g CP/kg in chicks fed on DEF diets, whereas food intake of chicks fed on BAL diets increased only between 30 and 100 g CP/kg, after which it decreased between 100 and 220 g CP/kg. 4. Protein efficiency ratio (g gain per g protein intake) decreased with each incremental increase in CP between 30 and 260 g CP/kg, regardless of whether diets were BAL or DEE 5. These data indicate that maintaining a balanced ratio of amino acids is a preferable approach when poultry producers are interested in employing low CP diets for economic, physiological or environmental reasons.

Animals↗

PubMed2000

Excess dietary methionine markedly increases the vitamin B-6 requirement of young chicks.

A soy-protein isolate diet that contained essentially no bioavailable vitamin B-6 was used to establish the quantitative effect of excess dietary methionine on the vitamin B-6 requirement of young chicks. When made adequate in vitamin B-6, chicks fed the basal diet required 2 g/kg supplemental DL-methionine to achieve maximal growth, and 10 g/kg additional DL-methionine (total = 12 g/kg) was found to be a tolerable excess level that would not depress voluntary food intake or growth rate. When chicks were fed seven graded doses of supplemental pyridoxine (PN) in diets that contained either adequate (2 g/kg) or excess (12 g/kg) methionine, the vitamin B-6 requirement for maximal growth was found to increase (P: < 0.01) from 0.73 to 1.05 mg/kg, a 44% increase, when 10 g/kg excess methionine was present in the diet. Indeed, this level of excess dietary methionine depressed (P: < 0.01) growth at all PN dose levels < or =1 mg/kg, but not at PN doses of 1.2 or 1.4 mg/kg. Because dietary intakes of both vitamin B-6 and methionine can affect plasma homocysteine levels, dietary methionine (and protein) intake should be considered important factors in setting safe and adequate requirement levels for vitamin B-6.

Animals↗

PubMed2000

Nutritional evaluation of low phytate and high protein corns.

Three chick experiments and two cecectomized rooster experiments were conducted to determine P bioavailability and amino acid (AA) digestibility in two low phytate corns (LP), a high protein corn (HP), and a corn containing both low phytate and high protein content (HP/LP) compared with conventional corn (CONV). From 8 to 20 or 21 d of age, 1-wk-old New Hampshire x Columbian chicks were fed a cornstarch-dextrose-soybean meal (SBM) basal diet containing 0.10% available P or the basal diet supplemented with two concentrations of P (0.05 or 0.06% and 0.10 or 0.12%) from KH2PO4 or two concentrations of the corns (20 or 21% and 40 or 42%). Bioavailability of P based on tibia bone ash was much higher for LP than for CONV; values ranged from 21 to 40% for CONV and from 59 to 95% for LP. Digestibility of AA in cecectomized roosters indicated no significant differences (P > 0.05) between CONV and HP in the first rooster experiment. Digestibilities of eight AA, including lysine, methionine, and arginine, in LP and HP/LP were higher (P < 0.05) than those in CONV in the second rooster experiment. The results of this study indicated that the P in LP was two to three times more bioavailable than the P in CONV and that the digestibilities of AA in HP/LP were equal to or higher than those in CONV.

Amino Acids↗

PubMed2000

Protein and energy evaluation of soybean meals processed from genetically modified high-protein soybeans.

A conventional and two genetically modified soybean samples were processed to dehulled soybean meal (SBM) at a pilot plant and were compared with SBM from a commercial processing plant. Crude protein levels (%) of the experimental SBM samples were M700, 52.5; M702, 53.4; and M703, 62.7. The commercial SBM sample (UI) contained 47.5% protein. Amino acid, gross energy, lipid, and fiber analyses were carried out, and true metabolizable energy and true amino acid digestibility were determined with adult cecectomized cockerels. Digestible Lys, Met, Cys, Thr, and Val, and also TMEn, were higher (P < 0.05) and NDF, fat, and phospholipids were lower in M703 than in the other SBM samples. The results of this study indicate that M703 has considerable advantages over conventional SBM as a feed ingredient for broiler chickens.

Amino Acids↗

PubMed2000

Citric acid does not improve phosphorus utilization in laying hens fed a corn-soybean meal diet.

Data previously obtained from our laboratory have indicated that citric acid was very effective at improving phytate-P utilization in chicks fed a P-deficient corn-soybean meal (SBM) diet. The objective of the current study was to determine if citric acid would have similar effects in a commercial strain of Single Comb White Leghorn laying hens (n = 432) fed a corn-SBM diet containing 0.10% available P (AP). Dietary treatments were a corn-SBM basal diet (0.10% AP, 3.8% Ca, and 17% CP) supplemented with 0, 1, 2, 3, or 4% citric acid and a positive control diet containing 0.45% AP. Each of the six dietary treatments were fed to six replicate groups of 12 hens from 22 to 40 wk of age. No significant differences in performance were observed among treatments during the first 4 wk of the experiment. Hen-day egg production, feed consumption, feed efficiency, and egg yield were subsequently depressed in hens fed 0, 1, 2, 3, or 4% citric acid compared with hens fed 0.45% AP. The results of this study indicate that citric acid does not improve the utilization of dietary P in laying hens fed a corn-SBM diet containing 3.8% Ca.

Aging↗

PubMed2000

Growth-promoting efficacy in young pigs of two sources of zinc oxide having either a high or a low bioavailability of zinc.

Commercial sources of zinc oxide (ZnO) differ widely in Zn relative bioavailability (RBV), but it is unknown whether growth-promoting efficacy in young pigs is influenced by RBV of the ZnO sources used. We compared a low-RBV (39%) ZnO manufactured by the Waelz process (W) to a high-RBV (93%) ZnO manufactured by the hydrosulfide process (HS). Antibacterial agents were included in the diet in only one of the four trials (Exp. 4). In Exp. 1, pigs (n = 36, 6.5 kg, 28 d of age) were randomly assigned in three replicates to receive 0, 1,500, or 3,000 mg Zn/kg from HS Zn in a 21-d growth assay. Growth rates and feed intake responded linearly (P < 0.01) to incremental doses of Zn. In Exp. 2, pigs (n = 60, 6.1 kg, 28 d of age) were randomly assigned in five replicates to receive either 0 or 1,500 mg W or HS Zn/kg during a 21-d feeding period. Growth performance was improved (P < 0.01) by the addition of ZnO. During wk 1, however, pigs receiving HS Zn grew faster (P < 0.03) than those receiving W Zn, but the difference diminished to a trend (P < 0.08) during wk 2. Morphology of duodenal, jejunal, and ileal intestinal sections was examined at d 21 of the assay, but neither source of ZnO had an effect on crypt depth or on villus height or width. In Exp. 3, weaned pigs (n = 48, 5.4 kg, 21 d of age) were randomly assigned in four replicates to the same dietary treatments as in Exp. 2 for a 17-d growth assay. Growth performance was improved (P < 0.05) by the addition of ZnO, but no difference was detected between the two sources. In Exp. 4, pigs (n = 60, 6.2 kg, 28 d of age) were randomly assigned in five replicates to receive either 0 or 1,500 mg/kg W or HS Zn in an 11-d growth assay wherein antimicrobial agents were included in the basal diet. Growth rates during the first 6-d were improved (P < 0.06) by the addition of ZnO, with a trend (P < 0.10) for greater weight gain in pigs receiving HS than in those fed W Zn. During the entire 11-d, however, there was no difference in growth rates between pigs fed the two sources of ZnO. In conclusion, RBV of Zn in ZnO did not substantially affect the growth-promoting efficacy of ZnO in young pigs fed diets with or without antimicrobial agents.

Animal Feed↗

PubMed2000

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.

Animal Feed↗

PubMed2000

The effects of citric acid on phytate-phosphorus utilization in young chicks and pigs.

Several bioassays were conducted with young chicks and pigs fed phosphorus (P)-deficient corn-soybean meal diets. With diets for chicks containing .62% Ca and .42% P (.10% available P), graded doses of a citric acid + sodium citrate (1:1, wt:wt) mixture (0, 1, 2, 4, or 6% of diet) resulted in linear (P < .01) increases in both weight gain and tibia ash. Relative to chicks fed no citric acid, tibia ash (%) and weight gain (g/d) were increased by 43 and 22%, respectively, in chicks fed 6% citric acid. Additional chick trials showed that 6% citric acid alone or sodium citrate alone was as efficacious as the citric acid + sodium citrate mixture and that 1,450 U/kg of phytase produced a positive response in bone ash and weight gain in chicks fed a diet containing 6% citrate. Varying the Ca:available P ratio with and without citrate supplementation indicated that citric acid primarily affected phytate-P utilization, not Ca, in chicks. Moreover, chicks did not respond to citrate supplementation when fed a P-deficient (.13% available P), phytate-free casein-dextrose diet. Young pigs averaging 10 to 11 kg also were used to evaluate citric acid efficacy in two experiments. A P-deficient corn-soybean meal basal diet was used to construct five treatment diets that contained 1) no additive, 2) 3% citric acid, 3) 6% citric acid, 4) 1,450 U/kg phytase, and 5) 6% citric acid + 1,450 U/kg phytase. Phytase supplementation increased (P < .01) weight gain, gain:feed, and metatarsal ash, whereas citric acid addition increased only gain:feed (P < .05) and metatarsal ash (P < .08). A subsequent 22-d pig experiment was conducted to evaluate the effect of lower levels of citric acid (0, 1, 2, or 3%) or 1,450 U/kg phytase addition to a P-deficient corn-soybean meal diet. Phytase supplementation improved (P < .01) all criteria measured. Weight gain and gain:feed data suggested a response to citric acid addition, but this was not supported by fibula ash results (P > .10). The positive responses to phytase were much greater than those to citric acid in both pig experiments. Thus, dietary citric acid effectively improved phytate P utilization in chicks but had a much smaller effect in pigs.

6-Phytase↗

PubMed2000

Zinc bioavailability in soybean meal.

A phytate-containing soy protein concentrate (SPC) diet (13.5 mg Zn/kg) and a phytate-free egg white diet (.3 mg Zn/kg) were used to determine the relative bioavailability (RBV) of Zn in dehulled soybean meal (SBM) based on Zn depletion-repletion growth bioassays in young chicks. After a 4-d Zn depletion period, chick weight gain responded linearly (P < .01) to graded increments of supplemental Zn (0 to 10 mg/kg) from ZnSO4 x 7H2O, whether added to the Zn-deficient SPC or egg white diet. Slope, however, was over twice as great for the standard curve relating weight gain to supplemental Zn intake for the egg white diet as for the SPC diet. Addition of 7 to 10 mg Zn/kg from SBM to either Zn-deficient diet increased (P < .01) weight gain, but a similar SBM addition to either diet made adequate in Zn did not increase weight gain. Using standard-curve methodology, RBV of Zn in SBM was 78% when the the SPC diet was used, but it was only 40% when the egg white diet was used. The phytate contained in the SPC basal diet therefore markedly reduced the efficiency of utilizing the supplemental inorganic Zn from ZnSO4 x 7H2O. This lowered the slope of the standard curve so that, on a relative basis, the Zn in SBM had a higher RBV value than was the case for Zn utilization in SBM with the phytate-free egg white diet. The 78% Zn RBV value in SBM would seem to have the greatest relevance for practical-type corn-SBM diets.

Animal Feed↗