Aves species have become valuable models for numerous experimental and biotechnological purposes due to their unique embryological and physiological traits. This review integrates recent progress and new insights into the molecular and physiological mechanisms of transgenic fowl production. Recent reports have indicated that birds are essential for studying vertebrate development and the conservation of endangered bird species, as well as serving as bioreactor hens. Over the last decade, germ cells and genetic modification have become pivotal components for the production of transgenic animals. Three prerequisites must be met for successfully producing transgenic fowl: the effective manipulation of various types of avian pluripotent cells without the loss of differentiation capacity, the manipulation of genes of interest without altering normal gene function, and increasing the efficiency of germ line chimera production. An understanding of the cellular and molecular signals that regulate germ cells as well as the development of a stable gene delivery method will make these species indispensable tools for basic research and biotechnological applications.
In this article we review the results of recent proteomic, transcriptomic and genomic analyses of the eggshell constituents and draw attention to the impact of this data on current understanding of eggshell mineralization. The most abundant constituents of the chicken eggshell have been identified. An exciting new approach is to determine which genes are upregulated during the onset of mineralization. New information from studies with purified native or recombinant eggshell proteins are necessary for in vitro tests to gain insight into the role of each isolated matrix component, and eventually to learn how they may function synergistically. One important goal will be to determine the impact and importance of posttranslational modification of matrix components (glycosylation, glycanation, phosphorylation, etc.), which could greatly alter their properties and interactions. These investigations will continue to provide new insights into function of integrated defense strategies that operate at biomineralized barriers. Genes involved in the physical or chemical defense of the egg are functional candidates for marker assisted selection to improve egg and eggshell quality.
The present study was conducted to investigate the effects of varying dietary protein levels on amino acid digestibility at different sites of fistulized chicken intestines. Chickens were fistulized to either the middle part of the jejunum (MJ), the distal end of the jejunum, the middle part of the ileum, the distal end of the ileum or the distal end of the rectum (DR). Intestinal digesta were collected from each site of the intestine, and contents of amino acids were measured. The true digestibilities of all amino acids in intestinal digesta at MJ were significantly lower than those at DR in the 10% protein group. In the 15% protein group, the true digestibilities of Asp, Thr, Glu, Pro, Gly, Val, Met and Ile in intestinal digesta at MJ were significantly lower than those at DR. The true digestibility of Ser in intestinal digesta at MJ was significantly lower than that at DR in the 20% protein group. In the 30% protein group, there was no significant difference in the true digestibilities of amino acids in intestinal digesta between the sites of the intestine. The true digestibilities of all amino acids in intestinal digesta at MJ in the 10% protein group were significantly lower than those in other groups. These results clearly demonstrated that dietary protein levels influence amino acid digestibility at MJ in chickens.
The present study was conducted to investigate the effects of varying dietary fat levels (3%-10%) on amino acid digestibility at different sites of fistulized chicken intestines. Chickens were fistulized to either the middle part of the jejunum (MJ), the distal end of the jejunum (DJ), the middle part of the ileum, the distal end of the ileum or the distal end of the rectum. Intestinal digesta were collected from each site of the intestine, and contents of amino acids were measured. True digestibilities of individual amino acids were not affected by the sites of intestines in the 3, 5 and 8% fat groups. The true digestibility of total amino acid in intestinal digesta at the MJ was significantly lower than that at the DJ in the 10% fat group. In addition, true digestibilities of individual amino acids at the MJ tended to be lower than those at the DJ in the 10% fat group. Comparison of the data at the MJ between groups showed that the true digestibilities of total amino acid and Met in intestinal digesta in the 10% fat group were significantly lower than those in other groups. The true digestibilities of all amino acids, except for Met, in intestinal digesta at the MJ in the 10% fat group tended to be lower than those in other groups. These results suggest that dietary fat levels influence the digestion of amino acids at the proximal part of the jejunum in chickens.
The influence of varying dietary proteins levels from 0% to 18%, which is the level of dietary protein requirement, on plasma IGF-I concentration and tissue IGFBP-2 and -4 gene expression was examined. Body weight gain was gradually lowered by decreasing dietary protein levels from 18% to 4.5%, and body weight was lost when chickens fed a protein-free diet. Plasma IGF-I concentration of chickens fed the 18% crude protein diet was the highest of all, and it was gradually decreased by reducing dietary protein concentrations. Gene expression of IGFBP-2 in the gizzard was elevated by decreasing dietary protein levels from 18% to 9%, and the further reduction in dietary protein content lowered gizzard IGFBP-2 gene expression. No significant change in hepatic IGFBP-4 gene expression was observed in chickens fed experimental diets with varying dietary protein levels. Multiple linear regression analysis revealed that the influence of the change in plasma IGF-I concentration and gizzard IGFBP-2 gene expression on body weight change of chickens fed varying amounts of dietary protein seemed to be independent because the interactive effect of both factors on body weight change was not significant.
An experiment was conducted to compare the effect of non-encapsulated liquid lactic acid produced by Bacillus coagulans fermented molasses and its encapsulated form of lactic acid on broiler performances, intestinal characteristics and intestinal microflora. Ninety six 1-day-old COBB broiler chicks were subjected to 8 different dietary groups, namely 2 forms of acidifier (non-encapsulated liquid and encapsulated) lactic acid and 4 levels of inclusion (0.2, 0.4, 0.6 and 0.8%). The results showed that encapsulated lactic acid significantly improved (P<0.01) broiler performances, reduced (P<0.05) intestinal pH, increased (P<0.05) intestinal villi length and reduced (P<0.05) only the number of Salmonella sp. With regard to level of lactic acid in the diet, it significantly affected (P<0.01) villi number and length, the number of lactic acid bacteria, and Escherichia coli. It is concluded that the use of 0.6% encapsulated lactic acid might be included in the broiler diet to improve performances.
The experiment was conducted to determine the apparent metabolizable energy (AME) or nitrogen-corrected metabolizable energy (AMEn) content of a high protein meat and bone meal (MBM) in broiler diets contain graded levels of wheat. Two hundred eighty-eight 14-d old broilers were allocated to six dietary treatments in a randomized complete block design and a2×3 factorial arrangement of treatments namely two levels of MBM (0 and 80g/kg) and three levels of wheat (0, 100 and 200g/kg). Wheat replaced part of corn and soybean meal and MBM was added at 0 or 80g/kg at each level of wheat. The birds received the diets for 7 d, and excreta were collected on d 19 to 21. The substitution of corn and SBM by wheat (200g/kg) increased the total NSP content in the diet by 11g/kg. There was a 5% decrease in both AME and AMEn when the level of wheat in the corn-SBM was increased to 200g/kg but this decrease was not significant. On the average, irrespective of wheat levels, AME and AMEn of the MBM were 2,734 and 2,586kcal/kg, respectively. Dietary AME and AMEn were greater in the diets with 200g/kg wheat compared to corn-SBM diet (P<0.05), and N excretion was greater (P<0.01) in the diets with MBM. Our results suggest that replacing part of corn and soybean meal with up to 200g/kg of wheat similar to what was used in the current study would have no effect on metabolizable energy of MBM.
The aim of this study was to examine whether treatments of chicks with probiotics affect the population of cells containing interleukin-6 (IL-6) and IgA in the intestine of broiler chicks. The diets with probiotics, Streptococcus faecalis, Clostridium buthricum, Bacillus mesentericus, were fed from day 0 to 10 of age. The sections of duodenum, pouch and tonsil region of cecum and colon were immunostained for IL-6 and IgA. The IL-6 immunoreaction products were identified in the leukocytes locating in the subepithelial tissues under the mucosal and crypt epithelium and lamina propria, and occationally in the the mucosal and crypt epithelium, in all birds. The density of immunoreactive (ir) IL-6 cell population in the mucosa tended to be lowest in the duodenum and highest in the colon. The density did not differ between control and probiotics groups on day 5; however, that in the cecum pouch and colon was significantly greater in the probiotics group than control on day 10. The IgA immunoreaction products were identified in the mucosal and crypt epithelial cells in all segments of the intestine, and some IgA-positive cells were localized in the lymphoid tissue in the cecum tonsil, whereas differences in their localization were not observed between probiotics and control groups. In conclusion, we suggest that probiotics increases the population of irIL-6 cells in the cecum and colon mucosal tissues of chicks. Because IL-6 is multifunctional cytokine for immune system, the increased IL-6 secretion may affect the immune functions in the intestinal mucosal tissues.
Maternal immunoglobulin (Ig) Y, the avian counterpart of mammalian IgG, is efficiently transported into the yolks of maturing oocytes. We have previously shown that the Fc region plays a critical role in the IgY transport into avian egg yolks. The aim of this study was to produce recombinant IgY-Fc and to evaluate its transport ability into avian egg yolks. Two basic expression vectors were constructed: one mainly expressed three constant regions of chicken IgY heavy chain (Fcυ2-4) that contained three cysteine residues (C252, C340, C347) involved in inter-heavy chain disulfide bonds; and the other mainly expressed two constant regions (Fcυ3-4) that contained two cysteine residues (C340, C347). SDS-PAGE and Western blotting analyses indicated that both Fcυ2-4 and Fcυ3-4 were separated into multiple protein bands under non-reducing conditions, suggesting incomplete formation of inter-chain disulfide bonds. To prevent the incomplete disulfide bond formation, C340 and C347 were mutated individually to serine by site-directed mutagenesis. As expected, each of the mutated recombinant IgY-Fc produced a single protein band by SDS-PAGE analysis. When intravenously-injected into laying quail, the two mutants, Fcυ2-4C347S and Fcυ3-4C340S, were transported into the egg yolks at high levels, whereas the other two mutants, Fcυ2-4C340S and Fcυ3-4C347S, were transported into the egg yolks at lower levels. In conclusion, we have succeeded in producing a recombinant IgY-Fc retaining a high transport ability into the avian egg yolks; this protein will be provided as a useful tool for studying the mechanism of IgY transport into egg yolks.
Considering that a study of bioequivalence is not compulsory for drug registration in many Latin-American countries, a trial using a bioequivalent preparation of enrofloxacin (bENR) and a non-bioequivalent one (nbENR) was carried out in broilers to assess the maximum serum concentrations (Cmax) and area under the plasma drug-concentration vs. time profiles (AUC) obtained. Three levels of drug handling when delivering the medicated water to the birds have been identified in poultry producing units in Mexico i.e., poor, medium and high. The trial was carried out in eight thousand, divided in six groups with three replicates per group. Variables included in handing the medicated water were grouped to integrate the poor, medium and high groups. The highest AUC and Cmax values were obtained with the bENR handled under high standards (P<0.05). The nbENR, similarly handled, failed to achieve adequate values in these variables. Medium and poor drug management either with bENR or nbENR resulted in low to very low Cmax and AUC values, reaching a lowest value of Cmax of 0.17μg/mL, equivalent to 7% of the best Cmax (2.43μg/mL). It is concluded that excepting in the bENR handled with high standards, all groups showed insufficient Cmax/MIC and AUC/MIC ratios. Relevance of these findings for clinical efficacy and for the emergence of bacterial resistant strains is discussed.