Browsing by Author "Kornegay, Ervin T."

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    Application of microbial phytase and its influencing factors in vivo and in vitro
    Qian, Hao (Virginia Tech, 1995)
    Five experiments were conducted in vivo to investigate the efficacy of phytase in improving the availability of phytate P as influenced by dietary Ca:total P (tP) ratios for pigs, broilers, and turkey poults. In pigs and poultry, microbial phytase was effective in improving performance, P and Ca digestibility, bone mineralization, and in decreasing fecal P excretion by enhancing hydrolysis of phytate P for young pigs, broilers and turkey poults fed a corn-soybean meal diet. Maximum responses were achieved at supplemental phytase levels of 750 to 1,050 units (U)/kg diet for young pigs and 600 to 900 U/kg diet for poultry. Based on nonlinear and linear response equations generated from the phytase and available P (aP) data in young pigs and non phytate P (nP) in broilers and turkeys, P-equivalency functions for phytase were developed. For pigs, the P-equivalency equation was Y = .2622(1 - .9706e⁻⋅⁰⁰¹⁸⁵ˣ); for broilers, the equation was Y = .2330(1 - .9818e⁻⋅⁰⁰⁰⁷⁴ˣ); and for turkey poults, the equation was Y = .1220(1 - 1.7721e⁻⋅⁰⁰⁵³ˣ). For these three equations, X = added phytase (U/kg diet) and Y = P-equivalency values (%). Based on these equations, 1 g of P as inorganic defluorinated phosphate could be replaced by 300 and 208 U of phytase/kg of diet for pigs fed diets containing .07 and .16% aP, by 937 U of phytase for broilers fed with .27% nP diet, or by 340 and 511 U of phytase/kg diet for turkey poults fed diets containing .27 and .36% nP, respectively. Phosphorus-equivalency values of phytase were also obtained by generating P-equivalency functions at each P level and each Ca:tP ratio. The phytase efficacy was influenced by dietary Ca:tP ratios, P, and vitamin D₃ levels. In pigs and poultry, a wide Ca:tP ratio decreased phytase efficacy because all measurements were decreased as the dietary Ca:tP ratio became wider. In young pigs, widening the ratios from 1.2 to 2.0:1 resulted in a decrease in phytase efficacy of 21.1 and 12.1% for .07 and .16% aP diets, respectively. In poultry, widening the ratio from 1.4 to 2.0 led to a decrease in phytase efficacy by 7.3% for broilers fed diets containing .27% nP, and by 6.3 and 4.2% for turkey poults fed diets containing .27 and .36% nP, respectively. A synergistic effect of vitamin D₃ addition and phytase supplementation was observed for broilers. Addition of vitamin D₃ indicated a potential for improving utilization of phytate P and Ca in the presence and absence of microbial phytase. Average daily gain, apparent P digestibility and bone ash content were the most sensitive measurements to assess microbial phytase efficacy for the replacement of inorganic P for pigs and poultry. These measurements were also sensitive for assessing the effects of varying Ca:tP ratios and levels of P. In summary, 1 g of P from defluorinated phosphate could be replaced by 250 to 400, 600 to 950 and 340 to 550 U of phytase/kg diet, respectively for young pigs, broilers and turkey poults when they were fed a com-soybean meal diet. Dietary Ca:tP ratio of 1.2:1 for young pigs and 1.1 to 1.4:1 for poultry resulted in maximum phytase efficacy. An in vitro study was performed for the evaluation of effects of cations on the characteristics of microbial phytase from A. niger. A discontinuous assay was applied to assay A. niger phytase. The enzyme was observed to have a high affinity for sodium phytate with a Km of 62 µM and a Vmax of 139 U of specific activity per mg of phytase protein. Malachite green was used as the color reagent in the discontinuous assay, which increased the sensitivity 50 fold over molybdovanadate as the color reagent. All cations tested in vitro (Mg²⁺, Mn²⁺, Ca²⁺, Cr³⁺, Fe³⁺, Cu²⁺ and Zn²⁺) inhibited phytase activity, and imposed a competitive or mixed inhibition; a binding of cations with phytate also was involved in the inhibition by decreasing the effective substrate concentration. The inhibition by Ca²⁺ and Mg²⁺ caused only a partial inhibition because the enzymatic reaction rate was never reduced to zero and replots of slopes for Ca²⁺ and Mg²⁺ were hyperbolic. Cations of Zn²⁺, Cu²⁺, Fe³⁺, Cr³⁺ and Mn²⁺ gave a pure inhibition. A decreasing order of the inhibitory effect from cations was observed on the phytase activity: Zn²⁺ > Cu²⁺ > Fe³⁺ > Cr³⁺ > Ca²⁺ > Mn²⁺ > Mg²⁺ based on the Ki value that increased from a low value for Zn²⁺ to a high value for Mg²⁺. In summary, cations possess a potential for decreasing A. niger phytase activity by a competitive or mixed-type inhibition system; binding of cations with the phytate substrate also inhibited the activity of A. niger phytase.
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    An assessment of the effects of dietary folic acid supplementation on serum folates status, conceptus development and reproductive performance in gilts and sows
    Harper, Allen F. (Virginia Tech, 1992-04-05)
    The effects of dietary folic acid supplementation on serum folate status, conceptus development and reproductive performance in gilts and sows was investigated in a series of experiments. The specific objectives of the study were to: 1) to study the serum folates profile following rapid consumption of a single meal containing different levels of supplemental folic acid; 2) to study the effects of maternal folic acid supplementation on conceptus survival, growth and development prior to mid-gestation in gilts and sows; and 3) to study the effects of multiple levels of dietary folic acid supplementation on sow reproductive performance over four successive parities. In the first experiment (Chapter III), gilts fed a single, rapidly consumed meal, had a rapid increase in serum folates concentration during the first hour postprandial. Within eight hours after feeding, serum folates in the gilts had returned to near prefeeding levels. The results also suggest that supplementing the diet with increasing levels of folic acid over a range of 0 to 4 ppm results in more rapid postprandial uptake and elimination of folic acid from general circulation. In the second experiment (Chapter IV), supplementing the diet of first parity and third parity breeding sows with 2 ppm folic acid had no effect on litter size at day 45 of gestation. However, several measurements associated with placental and fetal growth were increased with folic acid supplementation. Results of a fifth parity trial with four levels of supplemental folic acid were variable and inconclusive. The implications of increased placental and fetal growth up to day 45 of gestation in the first and third parity sows is discussed. In the third experiment (Chapter V), a decline in serum folate concentration in pregnant sows from mating to mid- to late gestation was clearly demonstrated. Supplementing the sow's diet with folic acid over a range of 0 to 4 ppm resulted in a linear increase in serum folate concentration at mating, during gestation and at weaning. However, under the conditions of this experiment, folic acid supplementation had no significant effect on sow reproductive performance.
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    An assessment of the effects of dietary oil supplementation on fetal survival in gilts at 40 days of gestation
    Rigau, Alberto Pérez (Virginia Tech, 1993-06-15)
    Eighty-six crossbred (Duroc x Yorkshire) gilts were used in two trials (50 gilts in Trial 1 and 36 gilts in Trial 2) for an assessment of the effect of supplemental dietary fat during early gestation on fetal survival, fetal development, and fatty acid concentration in gilt plasma and fetal head and body. Three diets contained 4% (w/w) added fat either as coconut, soybean, or fish (menhaden) oils. A fourth diet was used as a control. On d 37 to 45 postbreeding, gilts were slaughtered and numerous fetal and ovarian measurements made. Two sets of four randomly selected fetuses per gilt from Trial 1 were prepared. Blood samples from each gilt were obtained on the day of slaughter for determination of the plasma fatty acid profile. Across both trials, percentage fetal survival did not differ according to treatment, but in Trial 2 fetal survival was higher (P < .06) for gilts fed fish oil, compared with the controls. The fatty acid profile of plasma of gilts and the conceptus tissues were similar; both were influenced by the fatty acid concentration of the diets. The ratio of n-3/n-6 fatty acids was higher in conceptus tissue than in maternal plasma and the ratio was higher (P < .05) for the fish oil diet compared with the other diets. The relatively high concentration of omega-3 fatty acids in fetal tissues supports the hypothesis that omega-3 fatty acids play a role in the development of the pig conceptus and contributes to improve fetal survival. However, the high percentage fetal survival observed in all the treatments may have masked benefits of supplemental oil.
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    Availability and distribution of copper in soils following eight annual applications of CuSO₄ or Cu-enriched swine manure
    Payne, Grover Garry (Virginia Polytechnic Institute and State University, 1986)
    Three field studies were established in 1978 and continued through 1985 in order to determine the effects of long-term Cu applications, as either CuSO₄ or Cu-enriched swine manure, at high application rates on corn (Zea mays L.) production. The studies were conducted on Bertie fine sandy loam (Aquic Hapludult), Guernsey silt loam (Aquic Hapludalf), and Starr clay loam (Fluventic Dystrochrept)-Dyke clay (Typic Rhodudult) soils in the Coastal Plain, Ridge and Valley, and Piedmont physiographic regions of Virginia, respectively. A laboratory incubation study was also conducted using the same soils to determine the effects of soil pH on the changes in forms of soil Cu present over a 256-day period following addition of CuSO₄ or Cu-enriched swine manure. Application of 336 kg Cu ha⁻¹ , as CuSO₄ , or up to 264 kg Cu, as Cu-enriched swine manure, from 1978 through 1985 had no adverse affects on corn grain yields or on Cu concentrations in corn ear leaves or grain. Copper concentrations in ear leaf tissue were increased only slightly (≤ 2.1 mg kg⁻¹) by the eight annual Cu additions with no increase in Cu content of grain being observed. Copper concentrations in both ear leaves and grain remained within normal levels. DTPA extractable Cu was linearly related to the cumulative amount of Cu applied to the three soils (r = 0.93 to 0.98, α= 0.01). Extractable soil Cu showed no relationship with Cu levels in grain or leaf tissue. Analysis of subsoil samples indicated little downward movement of the applied Cu due to leaching. Fractionation of the Cu in the three soils indicated increases in all fractions resulting from Cu treatments. Results of the laboratory incubation study showed that the distribution of applied Cu among soi 1 fractions was dependent on soil pH, length of time following Cu additions, and to some degree on the source of applied Cu. Levels of Ex-Cu and HOAc-Cu decreased with time and increasing pH. No consistent differences in Pyro-Cu were observed due to pH or length of incubation. Concentrations of Ox-Cu parallelled the levels of Fe and Mn in the soils and generally increased with time. Soils at low pH tended to contain less Ox-Cu than soils at higher pH levels.
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    Availability of zinc from an amino acid chelate in Zn depleted pigs
    Swinkels, Johannes W. G. M. (Virginia Tech, 1992)
    This study was conducted to compare the availability of Zn from two Zn sources, an amino acid chelate and ZnSO₄. In three experiments, 78 Zn depleted and 24 Zn adequate pigs were used. Pigs were depleted of Zn by feeding an isolated soy protein, semi purified diet containing 17 ppm Zn. Of the 78 depleted pigs, 60 pigs were Zn repleted. During Zn repletion in Exp. 1, depleted pigs were fed the low Zn diet supplemented with 5, 15, or 45 ppm Zn either as ZnSO₄ or as Zn amino acid chelate (ZnAAC). In Exp. 2 and 3, low Zn diets were only supplemented with 45 ppm Zn. Zinc adequate pigs, used in Exp. 1 and 2, were fed the 45 ppm supplemental Zn diets. To evaluate differences in site and rate of apparent Zn absorption, chromic oxide was added to the diets of depleted pigs in Exp. 1 and 3. In all experiments, a 24-d period was sufficient to severely deplete the porcine body Zn stores, and to cause parakeratosis and growth retardation. Serum Zn concentrations and serum ALP-activities of depleted pigs dramatically decreased (P < .01) during the first 14 d of Zn depletion. At the end of Zn depletion, Zn contents in liver, kidney, pancreas, brain, and small intestine tissues of pigs fed the low Zn diet were reduced (P < .01) by 10 to 40 % compared with the adequate pigs fed the ZnSO₄ and ZnAAC diets. In Exp. 2, the growth retardation was associated with a low (P < .05) serum mitogenic activity and pituitary RNA content of depleted pigs compared with pair-fed adequate pigs. Moreover, the growth hormone mRNA fraction tended to be reduced (P < .10) for the Zn depleted pigs. In Exp. 1, the apparent absorption of Zn was higher (P < .01) for pigs fed ZnAAC compared with the ZnSO₄ group; however, this was not confirmed in Exp. 3 unless coefficients were corrected for Cr recovery. Furthermore, absorption of Zn occurred primarily within jejunal and distal segments of the small intestine. In the balance of Exp. 3, disappearance rates of Zn, Cu, Fe and DM were higher (P < .01) in depleted pigs fed ZnAAC compared with ZnSO₄. The recovery of Cr also was different (P < .01) between pigs fed the ZnSO₄ (87 %) and ZnAAC (70 %) diets. Moreover, the moisture content of the fecal matter was 11 % higher (P < .01) for the ZnAAC group compared with pigs fed ZnSO₄. In Exp. 1, depleted pigs fed the 15 ppm ZnSO₄ and ZnAAC diets regained their ability to grow, however, replenishment of body fluid and tissue Zn pools did not occur within the 24-d Zn repletion period. Both the 5 ppm ZnSO₄ and ZnAAC groups did not respond to Zn repletion within a 12-d period. In all experiments, the rate and degree of repletion of body fluid and tissue Zn stores was not different between pigs fed the 45 ppm ZnSOq and ZnAAC diets, although a higher (P < .05) serum mitogenic activity was observed for the adequate pigs fed ZnAAC compared with ZnSO4. In conclusion, an amino acid chelate did not improve growth, or rate and degree of replenishment of body fluid and tissue levels of Zn compared with pigs fed ZnSO₄. However, ZnAAC may have influenced intestinal luminal conditions since a higher rate of disappearance of Zn, Cu, Fe, Cr, and DM was measured.
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    Bacterial and yeast preparations for starter and grower rations
    Kornegay, Ervin T.; Thomas, Horace R. (Virginia Agricultural Experiment Station, 1973-02)
    Antibiotic combinations were effective in stimulating growth, with the major effect being upon feed intake
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    Binding mechanism of K88ab pili produced by enterotoxigenic Escherichia coli
    Choi, Suk Ho (Virginia Polytechnic Institute and State University, 1987)
    Binding of K88ab pili by brush border membrane and mucus from pig small intestine was characterized by inhibition assay and Western blot. In Western blot, K88ab pili were bound by two major brush border membrane polypeptides with molecular weight of 61,500 and 57,000 in addition to numerous minor polypeptides and a major mucus polypeptide with molecular weight of 27,500. The results from Western blot assays with periodate oxidized and carbamylated brush border membrane and inhibition assay with brush border membrane glycopeptide suggest that amino groups (rather than carbohydrate) present on the protein moiety are a part of the recognition site for K88ab pili of receptor polypeptides in brush border membrane. Differences were obtained in the binding patterns of K88ab pili when brush border membranes were prepared from small intestines obtained from 2-, 21-, and 42-day-old piglets as well as adult hogs. Binding of K88ab pili by mucus polypeptides was greater when prepared from small intestines obtained from 2-day-old piglets than from piglets of other ages and adult hogs. In inhibition assay, most fractions from sow milk and colostrum inhibited binding of K88ab pili. After gel filtration of colostral whey, fractions which contained IgG, IgA, and IgM produced the strongest inhibition of K88ab binding. Among fractions prepared from cow milk, casein and skim milk significantly inhibited binding of K88ab pili. In Western blot, αs1-casein, immunoglobulin chains, and MFGM polypeptides in sow milk and colostrum were shown to be able to bind K88ab pili. Additionally, αs1-casein was the major protein in bovine milk responsible for binding K88ab pili. In dot blot assay, IgG as well as brush border membrane could strongly bind K88ab pili. However, bovine αs1-casein showed only weak binding of K88ab pili. Binding of K88ab pili to these proteins and brush border membrane was inhibited by carbamylation and by addition of 100 mM D-galactosamine. The results suggest that the K88ab-binding proteins in milk and colostrum compete to bind K88ab pili with the receptors in the brush border membrane and that mechanisms involved in binding of K88ab pili by these proteins is similar to that by brush border membrane.
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    Characterization of Glycyl-Sarcosine Uptake by Ovine Intestinal Brush Border Membrane Vesicles
    Bowers, Sharon H. (Virginia Tech, 1997-08-19)
    In order to characterize peptide transport in the ovine small intestine, [14C]-glycyl-sarcosine uptake by tissue collected from five sheep was studied through the use of brush border membrane vesicles (BBMV). Preliminary experiments determined that incubation in hyaluronidase is not necessary in order to separate mucosal tissue from the basement membrane and that the stop solution used in the uptake study needed to be buffered. Uptake was examined in proximal (denoted jejunal) and distal (denoted ileal) halves of the intestine at four times (15, 30, 45, and 60 s) and at three extravesicular pH levels (6.4, 7.0, and 7.5). An intravesicular pH of 7.5 was used throughout the study. The two tissue sites differed (P < .02), with BBMV from jejunal tissue showing greater uptake than ileal. Uptake plateaued after 45 s, resulting in a quadratic (P < .005) effect of time. The effect of changes in extravesicular pH was also quadratic (P < .04), with uptake being greatest at pH 6.4, lowest at pH 7.0 and intermediate between the two at pH 7.5. Peptide uptake by sheep jejunal and ileal BBMV was demonstrated, but there was no clear evidence for increased uptake with decreasing extravesicular pH.
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    A comparison of feeding methods and 25 percent vs. 50 percent slotted floor for swine
    Thomas, Horace R.; Kornegay, Ervin T. (Virginia Agricultural Experiment Station, 1970-05)
    Two trials studied different feeding methods using pens with 25 and 50% slotted floors. There was no significant difference in the performance of pigs housed in pens with the 25 and 50% slotted floors
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    A comparison of high lysine corn and normal corn in combination with peanut oil for swine growing rations
    Thomas, Horace R.; Kornegay, Ervin T. (Virginia Agricultural Experiment Station, 1970-05)
    Although lysine content of high lysine corn was greater than that of normal corn it is not high enough to overcome completely the lysine deficiency of peanut meal as the major source of protein for growing pigs
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    Copper adsorption/desorption characteristics on copper amended soils
    Reed, Stewart T. (Virginia Tech, 1993)
    Laboratory tests were conducted to determine Cu availability of three Virginia soils amended with Cu as either Cu-rich pig manure or CuSO₄ with the same Cu content as that in manure. The study also assessed the capability of Mehlich-3 to estimate deficient and toxic Cu levels in soil. Application of Cu as manure or CuSO₄ did not affect grain yield or grain Cu concentration in corn grown at each site. Young corn plant height was reduced by CuSO₄ application on the Bertie sandy loam, an indication of greater toxicity from inorganic than organic Cu. Very little exchangeable or solution Cu was present in any of the three soils. The vast majority of Cu was distributed between the organic and soil oxide fractions. The ratio of soil oxide to organic matter determines the relative distribution of Cu among these fractions. Most organically bound Cu was held by specific adsorption mechanisms and Mehlich-3 strongly extracts this fraction. Mehlich-3 extraction patterns were indicative of Cu binding strength in the different soils. Since Mehlich-3 strongly extracts specifically bound Cu and only poorly removes oxide Cu, this test may underestimate Cu availability on sandy soils with low organic matter content. However, Mehlich-3 provides an acceptable test for soil Cu. Soil sorption characteristics were studied for Cu, Pb, and Zn added, both alone and simultaneously. Copper sorption energy was higher than both Pb or Zn, however, sorption capacity followed the order Pb > Zn > Cu. High Pb and Zn sorption was in part due to precipitation reactions especially at high initial solution concentrations. Zinc was bound to soil mostly by weak electrostatic forces. Copper and Pb were bound at specific sorption sites and by complex multi-site bonding mechanisms possibly involving organic substances. These specific and multi-site mechanisms account for metal ions removed from solution at low concentration. Even at low metal concentration, Cu and Pb sorption results in concurrent release of H⁺ and Ca²⁺ at a greater than one to one charge basis. Soils adjusted to various pH levels were equilibrated with Cu solution and then extracted with a series of dilute acid extractions to determine Cu adsorption and fixation capacities. Copper adsorption and more importantly Cu fixation increased with an increase in soil pH. Soil with a high organic matter content as a result of manure applications adsorbed and fixed more Cu at all pH levels than the control and CuSO₄ soil. The presence of organic matter may have a greater effect on metal sorption characteristics than maintenance of pH ≥ 6.5. Heavy metal sorption was accompanied by concurrent release of H⁺ and Ca²⁺ which represents exchangeable and specifically bound cation nutrients. Soils which receive heavy metal applications from sewage sludge or animal manure would have a short-term increase in plant available nutrients at the expense of long-term reserve capacity. Soil tests for cation nutrient availability on soils receiving heavy metal applications should be adopted to account for these responses.
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    Corn response to long-term application of CuSO₄, ZnSO₄ and Cu-enriched pig manure
    Gettier, Stacy W. (Virginia Polytechnic Institute and State University, 1986)
    Three studies, two field and one laboratory, were performed to evaluate Cu or Cu and Zn from either sulfate sources or Cu-enriched pig manure. The studies were designed to investigate the effects of Cu and Zn in soils and corn (Zea mays L.). The first field study consisted of continuing a longterm field experiment which was established in 1967 to evaluate corn response and changes in a Davidson clay loam soil to yearly additions of Cu and Zn sulfates. In 1983, the 17 annual additions of Cu and Zn resulted in cumulative totals of 280 kg Cu and 560 kg Zn ha⁻¹. These Cu and Zn additions, either alone or together, did not cause any grain or stalk yield decreases. The DTPA extractant effectively separated all soil treatment levels for both Cu and Zn. Copper concentrations in the blades and grain were not related to soil additions of Cu or Zn. However, Zn concentrations in blades and grain were directly related to each other, r=0.87**, to soil Zn treatment levels and to DTPA extractable Zn. The second field experiment was designed to evaluate the effects of soil application of Cu-enriched pig manure and CuSO₄ on corn. The five treatments in each of three field locations consisted of a control, low and high Cu-enriched pig manure levels, and Cu, as CuSO₄, equivalent to Cu amounts in the manure. The soils varied in texture from clay loam to fine sandy loam, and ranged in CEC from 5 to 12.3 cmol(+) kg⁻¹. Copper-enriched pig manure, containing 1285 mg Cu kg⁻¹, was produced by pigs fed diets supplemented with 242 mg Cu kg⁻¹. After six years, 198 mg Cu kg⁻¹ had been applied by the high treatments. The DTPA extractable Cu was not related to leaf nor grain Cu levels but was linearly related, r=O.95**, to applied Cu. No nutrient deficiencies or toxicities were observed. The third study was a laboratory incubation of added Cu. The 15 soils ranged from 54 to 489 mg kg⁻¹ in clay and from 5.4 to 7.4 in pH. Extractable Cu had simple correlations with five soil properties, clay, surface area, hydrous Al, hydrous Fe, and hydrous Mn. Three treatments, a control and 22 kg ha⁻¹ Cu as CuSO₄, and as Cu-enriched pig manure (equivalent to 975 mt wet manure ha⁻¹), were applied to the soils at 33 k Pa moisture. Copper was extracted in the following order for the control and CuSO₄, treatments: AlCl₃ in O.5M HC1 > EDTA > DTPA. A different order of Cu extraction occurred for the Cu-enriched pig manure treatment such that EDTA > DTPA > AlCl₃ in 0.5M HC1. Extractable Cu decreased with time regardless of Cu source.
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    Demonstration of peptide and free amino acid absorption by sheep forestomach epithelium using parabiotic chambers and identification of H⁺/peptide and free amino acid transport proteins in sheep omasal epithelium and bo,+ amino acid transport proteins in pig jejunal epithelium by expression of mRNA in Xenopus laevis oocytes
    Matthews, James Clyde (Virginia Tech, 1995-04-12)
    The absorption of methionine and methionylglycine (Met-Gly) across sheep (average BW = 38 kg) ruminal and omasal epithelia was studied using parabiotic chambers. Ruminal tissue demonstrated a greater ability to accumulate both substrates. Omasal tissue demonstrated a greater ability to translocate methionine and Met-Gly and a greater total absorption of both. Intact Met-Gly was transferred across both tissues. More was hydrolyzed by omasal epithelia. Within tissues, the total absorption of substrates did not differ. Evidence for carrier-mediated absorption was not observed. The ability to express exogenous mRNA in defolliculated Xenopus laevis oocytes was developed using sucrose gradient size-fractionated poly(A)⁺ RNA (RNA) isolated from the jejunal epithelial tissue of pig (average BW = 33.8 kg). Compared to water-injected oocytes, RNA injected oocytes displayed greater rates of Nat-independent lysine and leucine absorption. RNA-induced uptake of lysine (Kt = 52 uM) and leucine (Kt = 97 uM) was inhibited by 5 mM leucine and lysine, respectively, by .2 mM cysteine, but not by 5 mM glutamate. RNA-induced lysine and leucine absorption also was inhibited when oocytes were injected with RNA plus DNA oligomers that were complementary to the cloned human kidney b⁰‘⁺ transporter. Oocytes were injected with RNA isolated from omasal epithelial tissue of sheep (average BW = 67.5 kg) to identify potential peptide and amino acid transport proteins. Injection of specific RNA fractions induced greater rates of glycylsarcosine (Gly-Sar) uptake, as compared to water injection of oocytes. Media pH of less than 6.5 was required for induced Gly-Sar uptake. Induced Gly-Sar uptake required a pH of less than 6.5, was saturable (Kt = .40 mM), and was inhibited by 5 mM carnosine, Met-Gly, glycylleucine, but not by glycine. The RNA-induced Gly-Sar absorption was completely inhibited when oocytes were co-injected with RNA and DNA oligomers that were complementary to the cloned rabbit H⁺/peptide cotransporter. When oocytes were assayed for their ability to absorb lysine, RNA-induced lysine absorption was determined to be Na⁺-independent and to display b⁰‘⁺-like transport activity. Collectively, these results indicate that sheep omasal epithelia possess the potential to absorb free and peptide-bound amino acids by non-mediated processes and possess mRNA that encode for Ht-dependent dipeptide and b⁰‘⁺ transport protein activity. mRNA that encodes for b⁰‘⁺-like transport activity was identified in the jejunal epithelium of growing pigs.
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    Development and design of a test device for cartilage wear studies
    Burkhardt, Bettina M. (Virginia Tech, 1988-12-04)
    Articular cartilage is a material with the appearance of simplicity and uniformity, but the chemical and biological structure of this material is very complex and not yet known in every detail. Our knowledge of cartilage wear behavior is limited and needs to be enlarged. Knowledge in this area could be important for the prevention and treatment of degenerative joint diseases. Within the framework of this thesis. a literature search focused on the key words joint lubrication and cartilage wear was conducted. The result of this search was that almost all studies and experiments which have been carried out to investigate tribilogical processes in synovial joints focused on friction behavior. Only a few tests dealing with cartilage wear were conducted. Most of the cartilage wear studies were carried out under exaggerated conditions which might change the wear mechanisms. Two studies were undertaken under conditions close to normal conditions occurring in natural joints; one in entire joints with a pendulum device, the other one with a cartilage-on-cartilage test system. The test devices used in these tests offered no or limited opportunities for the variation of the test parameters. Test parameters are, for example, the type of motion, applied load, velocity, variation of the velocity during each cycle, type of specimen, and test fluid composition. In consideration of the findings of the literature search, it was decided to design a new test device providing the capability of measuring friction, wear, and displacement due to wear and/or cartilage deformation. Furthermore, the new test device for cartilage wear studies, allows the variation of the above mentioned test parameters.
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    Development of cassava (Manihot esculenta Crantz) leaf meal as an animal feed
    Ravindran, Velmurugu (Virginia Polytechnic Institute and State University, 1985)
    Research was conducted in Sri Lanka to evaluate the feasibility of developing cassava (Manihot esculenta Crantz) leaf meal as an animal feed. In feeding trials with broilers, improvements in performance were observed at 10% inclusion of cassava leaf meal (CLM). High levels (20 and 30%) of CLM depressed gain, feed intake and feed per gain. Weights of spleen and liver (% of body weight) linearly increased with increasing levels of CLM. Carcass pigmentation values favored the CLM-based diets. Dietary additives (methionine, sodium thiosulfate or soybean oil plus methionine) improved the growth of broilers fed 20% CLM diet without, however, having any beneficial effect when added to the basal diet. Gain of broilers tended to decrease with increasing dietary levels of cyanide. Feeding trials with growing pigs showed that CLM can be included up to 26.7% level without any effect on performance. Gain and feed per gain were improved at 13.3% CLM level, whereas marked depressions were noted at 40% CLM level. Results of the balance trials indicated that cassava leaf protein is utilized more efficiently by the pigs, although the nutrients in CLM are not as digestible as those in coconut oil meal. The overall results suggest that bulkiness, low energy content, methionine deficiency and presence of anti-nutritional factors, are the major factors limiting the high level use of CLM in non-ruminant diets. Studies on the processing of CLM revealed that simple drying is sufficient to eliminate almost 90% of the initial cyanide level in the fresh cassava leaves. A combination of chopping and 3-day wilting prior to drying proved most effective in lowering the cyanide level of CLM. Field trials conducted with a short-age cassava variety, MU 22, demonstrated that it is possible to increase cassava leaf dry matter yields by defoliating once during the growing season and to produce within 86% of the normal yield of roots. Two defoliations during the growing season depressed the root crop by more than half.
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    Double deck finishing of swine
    Thomas, Horace R.; Kornegay, Ervin T. (Virginia Agricultural Experiment Station, 1970-05)
    Result of this study is that pigs can be grown on double decks without getting reduced performance if the top deck is properly ventilated and insulated during hot summer months
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    Effect of feeding fumaric or citric acid on weanling pig performance and selected intestinal digesta measurements at varying times postweaning
    Risley, Chad Richard (Virginia Tech, 1990)
    Five studies were conducted to elucidate a possible mode of action of dietary organic acids in weanling pigs (n=536). The effect of feeding 1.5% fumaric or citric acid on growth performance, intestinal digesta pH, chloride ion concentration (Cl-), VFA profile and microflora populations was studied. In study 1, feeding citric acid improved ADG and feed conversion (F:G), whereas fumaric acid only numerically improved ADG and F:G. No significant dietary effect on intestinal pH, Cl- or VFA profile was observed. In study 2, feeding organic acids with and without a microbial supplement (Lactobacillus acidophilus) resulted in no interactive effects, but fumaric acid and the microbial supplement each improved ADG and F:G. In study 3, pigs fed organic acids were killed at -2, 0, 3, 7, 14 and 21 d postweaning. Organic acids had no significant effect on intestinal pH, Cl-, VFA profile or microflora populations. Postweaning age affected intestinal digesta measurements in these ways: pH decreased; VFA concentrations increased; lactobacillus decreased to d 3 postweaning; E. coli increased to d 7 postweaning; and clostridia decreased to d 21 postweaning. In study 4, pigs were fed organic acids and orally challenged with 10¹⁰ enterotoxigenic E. coli (0157:K88) (ETEC) at d 3, 7 and 14 postweaning. Organic acids had no measurable effect on intestinal pH, Cl- or VFA profile. ETEC challenge increased jejunum lactic acid concentration, lower colon VFA concentration and severity of scouring. Postweaning age affected these intestinal digesta measurements: cecum pH decreased; jejunum Cl- increased; jejunum lactobacillus count decreased; lower colon lactobacillus count increased; and E. coli count decreased in all intestinal sections. In study 5, pigs were fed organic acids and challenge with ETEC on d 3 postweaning. Organic acids had no significant effect on severity of scouring or protection against reduced growth performance from the ETEC challenge. The ETEC challenge resulted in an increased severity of scouring and a reduction in ADG of 20% and F:G of 19%. In summary, feeding organic acids generally improved weanling pig growth performance and had little effect on intestinal digesta measurements. Postweaning age did have an effect on intestinal digesta measurements. The primary mechanism of action of dietary organic acids does not seem to be the lowering of intestinal pH or modifications to the intestinal microflora, but may act as an additional energy source.
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    The effect of feeding varying levels of Bifidobacterium globsum a on the performance, scouring index, gastrointestinal measurements and immunity of weanling and growing-finishing pigs
    Agar, Gary A. (Virginia Tech, 1991-08-14)
    Four trials using 312 weanling pigs (average initial wt of 7.2 kg) were conducted to examine the effectiveness of Bifidobacterium globsum a (BGA) on the growth performance, scour scores, humoral and cell-mediated immune response and pH and chloride ion concentration (CIC) of feces and gastrointestinal section contents. The effect of continuous feeding of BGA from weaning to market weight on performance and carcass characteristics was evaluated using pigs from Trial 3 (n=80). Dietary treatments were 0, 5.0 x 104 , 6.7 x 106 and 7.5 x 108 colony forming units (CFU)/d in Trial 1 and 0, 6.0 x 104 , 5.0 x 105 and 5.0 x 106 CFU/d in Trials 2 through 4 and the grower-finisher trial. In Trial 1, ADG was effected quadratically at wk 1-2 and 1-5 (P < .05) and wk 3-5 (P < .01) with pigs fed the medium (6.7 x 106 ) BGA level having higher ADG than control pigs. Quadratic diet effects were also observed for average daily feed intake (ADFI) at wk 1-2, 1-5 (P < .10) and 3-5 (P < .05) with pigs fed the medium level of BGA having greater ADFI than control.
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    The effect of high-fiber diets on nutrient utilization and intestinal morphology of growing pigs
    Moore, Robert J. (Virginia Polytechnic Institute and State University, 1986)
    Three balance experiments were conducted to determine the effects of dietary fiber on mineral balance and intestinal.morphology of growing pigs. Fiber sources were added to corn-soybean meal diets at levels which increased neutral-detergent fiber levels by 6 to 8%. In experiment 1, 10% oat hulls (OH) decreased Ca (P<.06) and Zn (P<.01) balances of pigs after a 7 d feeding period. Wheat bran (20%) increased Mg intake and balance (P<.02), but did not affect Ca and Zn balances. In experiment 2, pigs were fed diets (with or without supplements of Zn, Fe and Mg) containing 15% OH or soybean hulls (SH) for 5 d or 26 d. SH increased Fe intake and balance (P<.01) and ( Mg absorption (P<.01). Compared with balances at 5 d, Zn balance was similar, while Fe and Mg balances were higher at 26 d for pigs fed the basal (P<.05) or SH (P<.01) diets. However, Zn balance was lower (P<.05) at 26 d 1 but Fe balance did not change over time for pigs fed the OH diets. At each time period, Zn balance was not different between pigs fed the basal or high-fiber diets. In experiment 3, Ca, Zn and Mg absorption were not affected by 15% OH or SH or 20% alfalfa meal (AM) after 67 d or 39 d, although SH and AM increased Fe balance (P<.01). Intestinal surface morphology of 12 pigs fed in experiment 3 was examined by scanning electron microscopy. Villus morphology was variable in jejunum, ileum and colon, although evidence of villus blunting and folding accompanied by erosion of microvilli and loss of epithelial cells was observed in small intestine of some pigs fed the SH and AM diets. Damage was not consistent in all sites examined in individual pigs, and did not occur in all pigs fed any specific diets. Although Ca and Zn balances were decreased by OH in two of the balance trials, the inability of OH to consistently decrease mineral balance suggests that the ability of the pig to adapt to different diets may be sufficient to overcome the mild inhibitory effect on mineral absorption of some fiber sources. When viewed together, the results of the balance trials indicate that moderate amounts of dietary fiber have a minimal negative impact on mineral balance of pigs fed practical corn-soybean meal diets. However, the results also indicate that fiber sources such as SH and AM, are rich sources of some minerals for the pig, particularly Fe. Evidence of intestinal damage was evident in pigs fed the high-fiber diets. However, not all animals fed a particular diet were affected, which suggests that some pigs within a given population may be susceptible to detrimental effects of dietary fiber on intestinal structure or function.
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    Effects of added dietary fat and protein on the growth and carcass characteristics of turkeys
    Blair, M. E. (Virginia Polytechnic Institute and State University, 1986)
    Two experiments were conducted to quantitate the effects of several parameters on the growth, carcass characteristics and fat deposition of the turkey. In the first experiment, 0, 5, 10 or 15% fat from three sources (Fat 1, Fat 2 or Fat 3) was added to low (18%), standard (21%) or high (24%) protein diets fed to Nicholas Large White male turkeys from 8 to 22 weeks of age. Carcass quality as measured by fat deposition, carcass yield and breast meat yield was determined. The addition of each 1% added fat up to 10% increased body weight gain .72%. Feed consumption decreased 1.3% and feed efficiency increased 2.3% for each 1% added fat up to 15%. Addition of Fat 2 to the diet resulted in significantly better feed efficiencies as compared with Fat 1 or Fat 3. The feeding of low protein diets as compared with standard protein diets decreased body weight gain, feed consumption and feed efficiency 13.2, 5.7 and 8.1%, respectively. Addition of fat to the diet increased 22-week body weight and the amount of breast meat produced per kg feed consumed. For each 1% added fat to low and standard protein diets, leaf and gizzard fat deposition increased 10.2 and 8.0%, respectively. Feeding low protein diets resulted in a 10.4% decrease in body weight and a 19.5% decrease in breast meat yield. The increase in leaf and gizzard fat deposition from each 5% increment of added fat up to 10% was counteracted by a 3% increase in dietary protein. In the second experiment, both sexes of the Nicholas Large White, Jaindl Large White and Jaindl Medium White strains were fed standard (21%) or high (24%) protein diets containing 0, 5 or 10% added dietary fat from 8 to 28 weeks of age. Carcass quality as measured by yield of carcass parts, fat deposition and the composition of breast meat was determined at 16, 20, 24 and 28 weeks of age. The Nicholas strain of turkey had a greater growth rate and consumed less feed to reach heavier weights than the Jaindl Large strain. Addition of 10% fat to the diet decreased feed consumption 12% and increased feed efficiency 17%. Fresh carcass and breast meat yield increased with age of the turkey, indicating that marketing at younger ages does not take full advantage of the meat producing capability of the turkey. The Jaindl Large and Medium White strains averaged 6.8 and 6.9% more breast meat yield than the Nicholas strain. The Nicholas strain deposited 4.36 times more leaf fat and 1.84 times more lipid within the breast meat as compared to the Jaindl Large strain. Added dietary fat decreased fresh carcass yield .41% and breast meat yield .65%. Feeding high protein diets increased fresh carcass yield and breast meat yield .25 and .47%, respectively.