Influence of coccidiosis vaccination on nutrient utilization of corn, soybean meal, and distillers dried grains with solubles in broilers.

Two experiments were conducted to determine the impact of coccidiosis vaccination on the apparent ileal digestibility (AID) of nutrients and ileal digestible energy (IDE) in commonly used feed ingredients in broilers. Eight experimental treatments based on a factorial arrangement of coccidiosis vaccination (control with in-feed diclazuril [CTL] or vaccinated [VAC]) and 4 different diets were administered to male Cobb 500 broilers in floor pens containing 12 birds per pen. For the vaccinated group, a 3× dose of a live coccidiosis vaccine was given via oral gavage on the day of hatch. Experimental diets consisted of a basal diet and 3 test diets in which 30% of the basal diet was replaced with either corn, soybean meal (SBM), or distillers dried grains with solubles (DDGS) to allow for calculation of nutrient digestibility of individual ingredients by difference. Broilers were fed a common diet from 0 to 7 D and experimental diets from 7 to 12 D. On day 12, blood and ileal digesta were collected to measure plasma carotenoids and determine AID of nitrogen, ether extract, IDE (experiments 1 and 2), and amino acids (AA) (experiment 2). Vaccination increased (P < 0.05) excreta oocyst counts and decreased (P < 0.05) plasma carotenoids when compared with CTL birds. Interactive effects (P < 0.05) were observed for AID of nitrogen (experiment 1) which was reduced by vaccination in birds fed the corn diet and increased for birds fed DDGS. No differences (P > 0.05) in IDE were observed between VAC and CTL birds in either experiment, whereas vaccination decreased (P < 0.05) AID of ether extract independently of diet. Interactive effects (P < 0.05) were observed for AA digestibility, whereby digestibility of all AA was reduced by VAC in corn diets but generally increased AA digestibility of DDGS diets, with minimal impact on SBM diets. In conclusion, the impact of coccidiosis vaccination on nutrient and energy digestibility varied among ingredients; however, digestibility was minimally impacted or improved with DDGS.

Effects of a high level of phytase on broiler performance, bone ash, phosphorus utilization, and phytate dephosphorylation to inositol.

An experiment was conducted to evaluate how the addition of microbial phytase influenced growth performance, bone mineralization, tissue P content, apparent digestibility and retention, and inositol phosphate (IP) concentrations in broilers fed diets with varying mineral matrices from 2 to 23 d of age. At 2 d of age, chicks were randomly allotted to receive 1 of 6 experimental diets arranged as a 3 × 2 factorial of mineral matrix [control diet with 1.0% Ca and 0.5% non-phytate phosphorus (NPP); mineral matrix 1 with 0.84% Ca and 0.35% NPP; and mineral matrix 2 with 0.77% Ca and 0.29% NPP] and phytase supplementation (0 or 1,500 FTU/kg). Feed intake was influenced (quadratic, P = 0.012) by the mineral matrix, but no interaction or main effect of phytase were observed. Phytase increased (P = 0.011) BW gain regardless of the mineral matrix applied. Feed efficiency was not influenced (P > 0.05) by mineral matrix, phytase, or their interaction. Phytase increased bone ash content differentially across matrices (interaction, P < 0.01), and tibia P content was lowest in birds fed matrix 2 and highest in the control (linear, P < 0.05). Concentrations of P in muscle, spleen, and liver were not affected by treatment. An interactive effect (P < 0.01) was observed for apparent ileal digestibility (AID) of P, where phytase increased AID in matrix 1. An interactive effect (P < 0.01) was observed for apparent retention of P and Ca, where phytase reduced P and Ca retention in the control diet. A main effect (P < 0.01) of mineral matrix was observed for AID of Ca, with birds fed matrix 1 having the lowest AID of Ca compared with control and matrix 2 treatments. Phytase influenced (P < 0.05) IP concentrations differently across matrices. Overall, phytase and the mineral matrix, either as main effects or in an interactive manner, influenced growth performance, apparent nutrient digestibility and retention, bone and IP concentration responses in broiler chicks.

Influence of dietary calcium concentrations and the calcium-to-non-phytate phosphorus ratio on growth performance, bone characteristics, and digestibility in broilers.

Two experiments were conducted to determine the influence of dietary Ca concentrations (Experiment 1) and a combination of dietary Ca and non-phytate phosphorus (NPP) to create distinct Ca-to-NPP ratios (Experiment 2) in corn-soybean meal diets fed to broiler chickens from 2 to 23 d of age. In Experiment 1, dietary treatments consisted of 7 concentrations of Ca (0.4, 0.6, 0.8, 1.0, 1.2, 1.4, or 1.6% of the diet; 7 treatments total), and NPP concentrations were maintained at 0.3%. Increasing the dietary Ca concentration while maintaining 0.3% NPP elicited linear reductions (P < 0.01) in overall growth performance and tibia ash. Dietary effects also were observed for apparent retention of P and Ca, which decreased (P < 0.05) linearly or quadratically for birds receiving dietary treatments with Ca concentrations greater than 0.6%. In Experiment 2, diets were formulated to contain 3 concentrations of Ca (0.4, 1.0, or 1.6% of the diet) with NPP concentrations either constant at 0.45% or adjusted to maintain a dietary Ca-to-NPP ratio of 2:1 (6 treatments total). Growth performance was not influenced by Ca concentration or the Ca-to-NPP ratio. Tibia break force was lower (P < 0.01) in birds fed diets containing 0.4% Ca, regardless of the NPP concentration. Tibia ash increased (P < 0.01) as the dietary Ca concentration increased. Neither the dietary Ca nor NPP concentrations affected nitrogen retention (P > 0.05). Upon maintaining a constant 2:1 Ca-to-NPP ratio, P and Ca retention decreased (P < 0.01) at the highest Ca concentration. In conclusion, imbalanced Ca and NPP adversely influenced growth performance and nutrient retention of broilers, indicating the concentrations of Ca and NPP required to maximize bone structure and function may be higher than those required for performance.

The role of the beta-lactamase signal sequence in the secretion of proteins by Escherichia coli.

A derivative of pBR322 has been constructed that contains both a unique EcoRI restriction site right at the beginning of the signal codons of the beta-lactamase (bla) gene and a unique BstEII site just at the end of the bla signal codons. Although the signal peptide encoded by the new plasmid differs from the wild type (pBR322) by 2 amino acid residues (Ser 2 to Arg 2 and Ala 23 to Gly 23), the synthesis, transport, and processing of the beta-lactamase remain unchanged in Escherichia coli. Two deletion mutants, in which the bla signal codons have been almost completely excised, have also been constructed. Bacteria containing either of these plasmids produce, but do not secrete, an active beta-lactamase. Last, the bla signal codons have been precisely joined to the cDNA version of the triose phosphate isomerase (tpi) gene from chicken. Expression of this fusion gene in E. coli gives a hybrid protein that is neither secreted into the periplasm nor proteolytically processed. This result supports the view that there are characteristics of the mature protein that are necessary for the secretion across the inner membrane of E. coli.

Targeted point mutation that creates a unique Eco RI site within the signal codons of the beta-lactamase gene without altering enzyme secretion or processing.

A method has been developed for constructing site-specific mutations by using a strongly selectable marker on which to "piggy-back" a desired mutation that may be phenotypically silent. Using this approach, a new unique Eco RI restriction site has been generated at the beginning of the signal codons of the beta-lactamase gene of the plasmid pBR322. The consequential alteration of the second amino acid of the signal from Ser to Arg has no effect on either the transport or the processing of the beta-lactamase.

Antibody-dependent cell-mediated destruction of human erythrocytes sensitized in ABO and rhesus fetal-maternal incompatibilities.

Antibody-dependent cell-mediated cytotoxicity (ADCMC) was measured in a 51Cr-release assay with antibody-sensitized human red blood cells (RBC) as target cells and nonimmune isologous or autologous mononuclear peripheral blood leukocytes (MPBL) as effector cells. ADCMC was readily demonstrable within 6 hr and was independent of exogenous complement (C'). The specificity of the ADCMC reaction was determined by the antiserum employed. Anti-A, anti-B, anti-D, and anti-c sera were all active in ADCMC; the specific lysis was between 35 and 50% with antiserum dilution of 1/1,000, using 10(5) target cells and 10(6) MPBL. Anti-C, anti-E, and anti-e sera had no detectable activity. Sephadex column separation suggested that this activity was by antibodies of the IgG class. Cord RBC from infants with RhD fetal-maternal incompatibility were lysed by autologous or isologous MPBL in the absence of exogenous antiserum. ADCMC was between 22% and42% in cases with high direct Coombs' test, but was negative with low direct Coombs' test as in five cases of ABO incompatibility.