Biological characteristics for assessing low phosphorus intake in finishing swine

Three replicates of a randomized complete-block design in a 3 x 3 factorial arrangement of treatments involving 141 pigs were conducted to evaluate the effect of low P intake on various response criteria in swine from 65 to 95 kg body weight. Total dietary P levels of .09, .21 and .31% were each fed in a Ca:P ratio of 1.1, 1.5:1 or 2:1 for a 35-d experimental period. The basal diet was formulated using corn starch, dextrin and a soy protein concentrate with monosodium phosphate and limestone supplying desired treatment levels of Ca and P. Blood and bones were collected for mineral analysis. Gain and feed performance responses were not affected by Ca:P ration or dietary P level for the 35-d period. Serum inorganic P concentrations declined as Ca:P ratio increased, but increased as dietary P increased. Serum alkaline phosphatase activity increased with higher Ca:P ratios, and decreased as dietary P level increased. Percent bone ash was not influenced by Ca:P ratio, but increased as dietary P level increased. Bone-bending moment was influenced by Ca:P ratio, and increased linearly as dietary P increased. Dietary P level resulted in a linear increase in total bone and its ash component weight, and in the accretion of the ash and organic matrix component. These data suggest that between 65 to 95 kg body weight, percent bone ash was affected by dietary P level, while bone-bending moment, bone component weights, their accretion, both dietary p level and Ca:P ratio.     

Effect of injected and dietary iron in young pigs on blood hematology and postnatal pig growth performance

The relationship of injected Fe doses on blood hematology and pig growth performance during both preweaning and postweaning periods was studied. In Exp. 1, the effect of BW of 347 pigs injected with 200 mg of Fe (dextran) intramuscularly (i.m.) at birth on hemoglobin (Hb) and percent hematocrit (Hct) at weaning was assessed. As BW increased there was a decline (P < 0.01) in Hb and Hct. In Exp. 2, Fe injection doses and timing of injected Fe on blood hematology and pig growth were evaluated. Injections were as follows: 1) 200 mg of Fe at birth; 2) 300 mg of Fe at birth; or 3) 200 mg of Fe at birth + 100 mg of Fe at d 10. A total of 269 pigs were allotted within litter to 3 treatments. The 2 greater quantities of injected Fe (i.e., 300 or 200 + 100 mg of Fe) had similar but greater (P < 0.05) Hb and Hct values than pigs receiving 200 mg of Fe, but growth rates were similar at weaning. The effects of injecting 200 mg of Fe at birth and either saline or 100 mg of Fe at 10 d of age were investigated in Exp. 3. Weaned pigs of each group were fed diets with 0, 80, or 160 mg/kg of added Fe for 35 d as a 2 × 3 factorial arrangement with 12 replicates (n = 360 pigs) in a randomized complete block design (RCB). The innate Fe contents of diets averaged 200 mg/kg. The greater Fe injection group (200 + 100 mg) had greater (P < 0.01) Hb and Hct values through 14 d postweaning (P < 0.05) and greater (P < 0.01) Hct values through 21 d postweaning. As dietary Fe increased, Hb was greater only at d 14 (P < 0.05 4), whereas Hct increased linearly to d 35 (P < 0.01) postweaning. Dietary Fe resulted in linear increases (P < 0.01) in ADG from d 21 to 35 and d 0 to 35. In Exp. 4, 3 dietary Fe (80, 160, and 240 mg/kg of diet), 2 injected Fe treatments (200 or 300 mg of Fe) at birth, and birth BW (<1.5 or ≥1.5 kg) were evaluated as a 2 × 2 × 3 factorial arrangement of treatments in a RCB design with 6 replicates (n = 280 pigs). The 300 mg of Fe injection group had lighter BW in both birth BW groups, with a birth BW × injected Fe interaction (P < 0.01). This resulted in the lighter birth BW pigs receiving 200 mg of Fe having greater BW gains to 240 mg/kg of dietary Fe, whereas light birth BW pigs injected with 300 mg of Fe plateaued at 160 mg/kg of Fe. Pigs in the heavy birth BW group injected with 200 or 300 mg of Fe at birth responded similarly to dietary Fe postweaning. These results indicate that blood Hb and Hct were affected by pig BW at weaning, but the additional 100 mg of Fe i.m. at 10 d of age increased blood hematology and that Fe injected preweaning affected initial postweaning performance.     

Rearrangement of the bacterial chromosome: forbidden inversions

The order of genes in the chromosome of enteric bacteria has been evolutionarily conserved despite the existence of mechanisms for rearrangement. Homologous chromosomal sequences in the same orientation recombine to form deletions or duplications. When homologous sequences in inverse orientation recombine, one expects to form an inversion of the intervening chromosomal segment. This expectation was tested by placing pairs of homologous sequences in inverse order at various points in the chromosome. Sequences at many pairs of sites (permissive) do recombine to generate the expected inversion, while the same sequences placed at other pairs of sites (nonpermissive) do not form an inversion. For the one nonpermissive interval tested, the missing inversion type can be constructed by an alternative transductional method; strains with this inversion are viable. Thus mechanistic limitations must prevent sequences at particular sites from undergoing the recombination event required to form an inversion.     

Effect of soybean meal particle size on amino acid and energy digestibility in grower-finisher swine

A study was conducted using the ileal digestibility technique with grower-finisher pigs to evaluate the effects of particle size reduction of soybean meal (SBM) on amino acid and energy digestibility. Soybean meal was processed through a hammer mill to achieve average particle sizes of 900, 600, 300, and 150 microm. The treatments included the use of two soybean meal sources and soy protein concentrate. One source of SBM was ground to four different particle sizes (i.e., 949, 600, 389, 185); a second source was a common SBM source used in other trials (i.e., 800 microm). The soy protein concentrate had an average particle size of 385 microm. A low-protein (5% casein) diet was fed to determine endogenous amino acid losses. This experiment was conducted in a 7 x 7 Latin Square design in two replicates using 14 crossbred barrows ([Landrace x Yorkshire] x Duroc) that averaged 28 kg BW and 60 d of age. Animals were surgically fitted with a T-cannula at the distal ileum. Treatment diets were fed in meal form, initially at 0.09 kg BW(0.75) and at graded increases at each subsequent period. Pigs within replicate were fed a constant quantity of their treatment diet for a 5-d adjustment period followed by a 2-d collection of ileal digesta samples. Apparent and true digestibility of amino acids was calculated by use of chromic oxide (0.5%) as an indigestible marker. Apparent digestibility of isoleucine, methionine, phenylalanine, and valine increased linearly (P < 0.05) as particle size decreased. True digestibility of isoleucine, methionine, phenylalanine, and valine increased linearly (P < 0.05) as particle size decreased. When the essential amino acids were averaged, apparent digestibility increased (P < 0.10) from 83.5% to 84.9% as particle size decreased, whereas, nonessential amino acid digestibility increased only slightly (P > 0.15). Essential amino acid true digestibility increased numerically from 91.0% to 92.4% as particle size decreased. Energy digestibility was not affected by particle size (P > 0.15). These results suggest that a reduction in particle size of soybean meal resulted in a small increase in the digestibility of its amino acids with the essential amino acids being affected more than the nonessential amino acids. The largest improvement in digestibility, however, was obtained when the particle size was reduced to 600 microm.     

A preliminary study to evaluate the immune responses induced by immunization of dogs with inactivated Ehrlichia canis organisms

Ehrlichia canis is an intracellular pathogen that causes canine monocytic ehrlichiosis. Although the role of antibody responses cannot be discounted, control of this intracellular pathogen is expected to be by cell mediated immune responses. The immune responses in dogs immunized with inactivated E. canis organisms in combination with Quil A were evaluated. Immunization provoked strong humoral and cellular immune responses, which were demonstrable by Western blotting and lymphocyte proliferation assays. By Western blotting antibodies to several immunodominant E. canis proteins were detected in serum from immunized dogs and antibody titres increased after each immunization. The complement of immunogenic proteins recognized by the antisera were similar to those recognized in serum from infected dogs. Upon challenge with live E. canis, rapid anamnestic humoral responses were detected in the serum of immunized dogs and primary antibody responses were detected in the serum from control dogs. Following immunization, a lymphocyte proliferative response (cellular immunity) was detected in peripheral blood mononuclear cells (PBMNs) of immunized dogs upon stimulation with E. canis antigens. These responses were absent from non-immunized control dogs until after infection with live E. canis, when antigen specific-lymphocyte proliferation responses were also detected in the PBMNs of the control dogs. It can be thus concluded that immunization against canine monocytic ehrlichiosis may be feasible. However, the immunization regimen needs to be optimized and a detailed investigation needs to be done to determine if this regimen can prevent development of acute and chronic disease.     

In vitro growth-promoting activity of porcine mammary secretions: initial characterization and relationship to known peptide growth factors

We have examined the in vitro growth-promoting properties and growth factor content of porcine mammary secretions. Defatted, porcine colostrum stimulated the proliferation of fibroblast and epithelial-like cell lines of diverse species origins in serum-free medium and cellular DNA synthesis (4- to 119-fold) as monitored by uptake of 3H-thymidine into DNA of quiescent cells in culture. Porcine milk, although mitogenic, had reduced activity when compared with colostrum on an equivalent-volume basis. Furthermore, the relative mitogenic activity of milk, although still detectable at 3 wk, continued to decline with length of the lactation period. Fractionation of pig colostrum on gel-filtration columns revealed multiple peaks of (AKR-2B) fibroblast mitogenic activity (208, 66 and 4.6 kdaltons) and a heterogenous profile of epithelial cell mitogenicity. Polyclonal antibodies (IgG) specific for murine epidermal growth factor (EGF; the major mitogen in human and murine milk) or human platelet-derived growth factor (PDGF) did not inhibit the mitogenic activity of pig colostrum or milk, demonstrating lack of antigenic relatedness between the contributing porcine factors and mEGF or hPDGF. Also, we were unable to demonstrate similarity of the small Mr colostral factor with EGF by use of EGF radioreceptor assay. These results identify porcine colostrum and milk as sources of potentially important in vitro growth-promoting factors. The enhanced expression of these factors in early mammary secretions suggests their possible in vivo involvement in mammary and neonatal tissue growth processes.     

Dietary calcium and phosphorus levels for growing swine from 18 to 57 kilograms body weight

A randomized complete block design experiment was conducted using 408 crossbred pigs to evaluate the effects of six dietary Ca/P levels for growing swine (18 to 57 kg). Total dietary P levels ranged from .40 to .90% in .1% intervals with Ca concurrently increased at a 1.3:1 ratio in a 16% protein corn-soybean meal diet. Dicalcium phosphate and limestone were the source of inorganic Ca and P. For the overall trial, daily gain and feed intake improved as dietary Ca/P increased to an approximate level of .65/.50%. An inverse relationship occurred between serum Ca and P, with serum Ca declining and P increasing at the lower mineral levels. Femur, humerus, rib, metatarsal and metacarpal ash content increased quadratically (P less than .01) as dietary Ca/P increased with suggested dietary breakpoint inflections of .90% Ca and .70% P at 40 kg, and at .72/.55% levels at 57 kg body weight. Percentage ash of the head portion of the bone was lower than the shaft section. Bone shaft thickness and bending moments for metatarsals and metacarpals increased as dietary Ca/P levels increased, with higher values and higher dietary inflection points at 57 than at 40 kg body weight. Bone length was not influenced by dietary Ca/P level, but fat-free dried bone weight was, resulting in higher total bone ash and organic weight as Ca/P level increased.     

Thermal dependence of malate synthase activity and its relationship to the thermal dependence of seedling emergence

Cotton yields are often reduced by low temperatures at early planting dates. Improved seedling metabolism at low temperatures may enhance seedling performance. The glyoxylate cycle plays a role in the metabolism of stored lipids, and thus thermal limitations on the function of malate synthase (EC 4.1.3.2) may be involved in low-temperature limitations on seedlings. The thermal dependencies of the apparent K(M) and maximal velocity for the malate synthases from cotton (Gossypium hirsutum L.) and sunflower (Helianthus annuus L.) were determined across a 15-45 degrees C thermal range and used to estimate the thermal dependence of reaction velocity. The thermal dependence of seedling emergence was monitored for both species. The thermal dependencies of predicted reaction velocity and the measured rates of seedling emergence are correlated (cotton r(2) = 0.9, sunflower r(2) = 0.76) and suggest that the thermal dependencies of enzymes predicted from basic kinetic parameters may be useful indicators of the thermal dependence of more complex whole-plant processes.