Expression of small intestinal nutrient transporters in embryonic and posthatch turkeys.

Nutrients are absorbed in the small intestine through a variety of transporter proteins, which have not been as well characterized in turkeys as in chickens. The objective of this study was to profile the mRNA expression of amino acid and monosaccharide transporters in the small intestine of male and female turkeys. Jejunum was collected during embryonic development (embryonic d 21 and 24, and d of hatch (DOH)) and duodenum, jejunum, and ileum were collected in a separate experiment during posthatch development (DOH, d 7, 14, 21, and 28). Real-time PCR was used to determine expression of aminopeptidase N (APN), one peptide (PepT1), 6 amino acid (ASCT1, b(o,+)AT, CAT1, EAAT3, LAT1, y(+)LAT2) and 3 monosaccharide (GLUT2, GLUT5, SGLT1) transporters. Data were analyzed by ANOVA using JMP Pro 11.0. APN, b(o,+)AT, PepT1, y(+)LAT2, GLUT5, and SGLT1 showed increased expression from embryonic d 21 and 24 to DOH. During posthatch, all genes except GLUT2 and SGLT1 were expressed greater in females than males. GLUT2 was expressed the same in males as females and SGLT1 was expressed greater in males than females. All basolateral membrane transporters were expressed greater during early development then decreased with age, while the brush border membrane transporters EAAT3, GLUT5, and SGLT1 showed increased expression later in development. Because turkeys showed high-level expression of the anionic amino acid transporter EAAT3, a direct comparison of tissue-specific expression of EAAT3 between chicken and turkey was conducted. The anionic amino acid transporter EAAT3 showed 6-fold greater expression in the ileum of turkeys at d 14 compared to chickens. This new knowledge can be used not only to better formulate turkey diets to accommodate increased glutamate transport, but also to optimize nutrition for both sexes.

Expression of digestive enzymes and nutrient transporters in Eimeria-challenged broilers.

Avian coccidiosis is a disease caused by the intestinal protozoa Eimeria. The site of invasion and lesions in the intestine is species-specific, for example E. acervulina affects the duodenum, E. maxima the jejunum, and E. tenella the ceca. Lesions in the intestinal mucosa cause reduced feed efficiency and body weight gain. The growth reduction may be due to changes in expression of digestive enzymes and nutrient transporters in the intestine. The objective of this study was to compare the expression of digestive enzymes, nutrient transporters and an antimicrobial peptide in broilers challenged with either E. acervulina, E. maxima or E. tenella. The genes examined included digestive enzymes (APN and SI), peptide and amino acid transporters (PepT1, ASCT1, b(0,+)AT/rBAT, B(0)AT, CAT1, CAT2, EAAT3, LAT1, y(+)LAT1 and y(+)LAT2), sugar transporters (GLUT1, GLUT2, GLUT5 and SGLT1), zinc transporter (ZnT1) and an antimicrobial peptide (LEAP2). Duodenum, jejunum, ileum and ceca were collected 7 days post challenge. E. acervulina challenge resulted in downregulation of various nutrient transporters or LEAP2 in the duodenum and ceca, but not the jejunum or ileum. E. maxima challenge produced both downregulation and upregulation of nutrient transporters and LEAP2 in all three segments of the small intestine and ceca. E. tenella challenge resulted in the downregulation and upregulation of nutrient transporters and LEAP2 in the jejunum, ileum and ceca, but not the duodenum. At the respective target tissue, E. acervulina, E. maxima and E. tenella infection caused common downregulation of APN, b(0,+)AT, rBAT, EAAT3, SI, GLUT2, GLUT5, ZnT1 and LEAP2. The downregulation of nutrient transporters would result in a decrease in the efficiency of protein and polysaccharide digestion and uptake, which may partially explain the weight loss. The downregulation of nutrient transporters may also be a cellular response to reduced expression of the host defense protein LEAP2, which would diminish intracellular pools of nutrients and inhibit pathogen replication.

Removal of Mycobacterium avium subspecies hominissuis (MAH) from drinking water by coagulation, flocculation and sedimentation processes.

UNLABELLED: There has been a growing concern over human exposure to Mycobacterium avium subspecies hominissuis (MAH) through drinking water due to its ubiquitous presence in natural waters and remarkable resistance to both chemical and physical disinfectants in drinking water treatment processes. However, little is known about the effectiveness of physico-chemical water treatment processes to remove MAH. Therefore, we determined the removal of MAH by alum coagulation, flocculation and sedimentation processes in optimized drinking water treatment conditions using standard jar test equipment. Contrary to the prevailing hypothesis, the results of this study show that removal of MAH by coagulation, flocculation and sedimentation processes was only moderate (approx. 0.65 log10) under low turbidity treatment conditions and the removal of MAH was actually lower than that of Escherichia coli (reference bacterium) in all the waters tested. Overall, the results of this study suggested that coagulation, flocculation and sedimentation processes may not be a reliable treatment option for removing MAH, and more efforts to find an effective control measures against MAH should be made to reduce the risk of MAH infection from drinking water. SIGNIFICANCE AND IMPACT OF THE STUDY: Despite a growing concern over human exposure to Mycobacterium avium subspecies hominissuis (MAH) through drinking water and its remarkable resistance to water disinfectants, little is known about the effectiveness of physico-chemical water treatment processes to remove MAH. Contrary to the prevailing hypothesis, the results of this study suggest that coagulation, flocculation and sedimentation processes may not be a reliable treatment option for MAH removal. As these processes have been the last remaining conventional drinking water treatment processes that might be effective against MAH, more efforts should be urgently made to find an effective control measures against this important waterborne pathogen.

Changes in expression of an antimicrobial peptide, digestive enzymes, and nutrient transporters in the intestine of E. praecox-infected chickens.

Coccidiosis is a major intestinal disease of poultry, caused by several species of the protozoan Eimeria. The objective of this study was to examine changes in expression of digestive enzymes, nutrient transporters, and an antimicrobial peptide following an Eimeria praecox challenge of chickens at days 3 and 6 post-infection. Gene expression was determined by real-time PCR and analyzed by one-way ANOVA. In the duodenum, the primary site of E. praecox infection, a number of genes were downregulated at both d3 and d6 post-infection. These genes included liver expressed antimicrobial peptide 2 (LEAP2), the cationic (CAT1), anionic (EAAT3), and L-type (LAT1) amino acid transporters, the peptide transporter PepT1 and the zinc transporter ZnT1. Other transporters were downregulated either at d3 or d6. At both d3 and d6, there was downregulation of B(o)AT and CAT1 in the jejunum and downregulation of LEAP2 and LAT1 in the ileum. LEAP2, EAAT3, and ZnT1 have been found to be downregulated following challenge with other Eimeria species, suggesting a common cellular response to Eimeria.

Expression profiles of muscle genes in postnatal skeletal muscle in lines of chickens divergently selected for high and low body weight.

Long-term genetic selection for BW has generated high weight select (HWS) and low weight select (LWS) lines of chickens. These lines show an approximate 10-fold difference in BW at selection age (d 56). The objective of this study was to profile the expression of master regulators of early lineage specification (Pax3, Pax7) and myogenic regulatory factors (Myf5, MyoD1, MyoG, and Mrf4) on day of hatch and d 7, 28, and 56 in pectoralis major and gastrocnemius muscles. There was a line × age interaction for expression of all 6 genes in both muscles. In pectoralis major muscle, Pax3, MyoD1, and Mrf4 showed greater expression in LWS than HWS at day of hatch, whereas all 6 genes showed greater expression in HWS than LWS at d 28. In gastrocnemius muscle, Pax3, Myf5, MyoD1, and MyoG showed greater expression in LWS than HWS at day of hatch, whereas Pax7, Myf5, MyoD1, and Mrf4 showed greater expression in HWS than LWS at d 28. At day of hatch there was no difference in fiber number in gastrocnemius muscle between HWS and LWS; however, HWS had greater fiber diameter than LWS. These results indicate that in LWS there is enhanced expression of genes that are necessary for proliferation of progenitor muscle cells and muscle cell differentiation at day of hatch compared with HWS, but by d 28 these genes are expressed greater in HWS than LWS. Thus, long-term selection for growth has altered the pattern of muscle gene expression.

Expression of digestive enzymes and nutrient transporters in Eimeria acervulina-challenged layers and broilers.

Avian coccidiosis is a disease caused by intestinal protozoa in the genus Eimeria. Clinical signs of coccidiosis include intestinal lesions and reduced feed efficiency and BW gain. This growth reduction may be due to changes in expression of digestive enzymes and nutrient transporters in the intestine. The objective of this study was to examine the differential expression of digestive enzymes, transporters of amino acids, peptides, sugars, and minerals, and an antimicrobial peptide in the small intestine of Eimeria acervulina-infected broilers and layers. Uninfected broilers and layers, in general, expressed these genes at comparable levels. Some differences included 3-fold and 2-fold greater expression of the peptide transporter PepT1 and the antimicrobial peptide LEAP2 (liver expressed antimicrobial peptide 2), respectively, in the jejunum of layers compared with broilers and 17-fold greater expression of LEAP2 in the duodenum of broilers compared with layers. In the duodenum of Eimeria-infected broilers and layers, there was downregulation of aminopeptidase N; sucrase-isomaltase; the neutral, cationic, and anionic amino acid transporters b(o,+)AT/rBAT, B(o)AT, CAT2, and EAAT3; the sugar transporter GLUT2; the zinc transporter ZnT1; and LEAP2. In the jejunum of infected layers there was downregulation of many of the same genes as in the duodenum plus downregulation of PepT1, b(o,+)AT/rBAT, and the y(+) L system amino acid transporters y(+) LAT1 and y(+) LAT2. In the ileum of infected layers there was downregulation of CAT2, y(+)LAT1, the L type amino acid transporter LAT1, and the sugar transporter GLUT1, and upregulation of APN, PepT1, the sodium glucose transporter SGLT4, and LEAP2. In E. acervulina-infected broilers, there were no gene expression changes in the jejunum and ileum. These changes in intestinal digestive enzyme and nutrient transporter gene expression may result in a decrease in the efficiency of protein digestion, uptake of important amino acids and sugars, and disruption of mineral balance that may affect intestinal cell metabolism and Eimeria replication.

Expression of the peptide transporters PepT1, PepT2, and PHT1 in the embryonic and posthatch chick.

Peptide transporters 1 and 2 (PepT1 and PepT2) and peptide/histidine transporter 1 (PHT1) are all members of the proton-coupled oligopeptide transporter family, which are important for the transport of amino acids in peptide form. The PepT1 acts as a low-affinity/high-capacity transporter and PepT2 as a high-affinity/low-capacity transporter for di- and tri-peptides. The PHT1 transports di- and tri-peptides as well as histidine. The objective of this study was to profile PepT1, PepT2, and PHT1 mRNA expression in the proventriculus, duodenum, jejunum, ileum, ceca, large intestine, brain, heart, bursa of Fabricius, lung, kidney, and liver in layer chicks on embryonic d 18 and 20 and d 1, 3, 7, 10, and 14 posthatch. Absolute quantification real-time PCR was used to measure gene expression. Expression of PepT1 was greatest in the duodenum, jejunum, and ileum. Expression of PepT1 increased in the duodenum, jejunum, and ileum from late embryonic stages to posthatch and in the large intestine from late embryonic stages to d 10 posthatch. In the ceca, PepT1 expression increased from embryonic d 20 to d 1 posthatch and then decreased. Expression of PepT2 was greatest in the brain and kidney. Expression of PepT2 increased from d 10 to 14 in the bursa of Fabricius and decreased in the proventriculus, duodenum, jejunum, and liver from late embryonic stages to posthatch. In the small intestine and liver, PepT2 may function to transport di- and tri-peptides during embryogenesis. The PHT1 was expressed in all tissues analyzed. Expression of PHT1 increased in the jejunum, large intestine, brain, and liver posthatch and decreased in the proventriculus from embryonic stages to posthatch. A tissue × age interaction was observed for all genes. The uptake of peptides in the developing chick is regulated by peptide transporters that are expressed in a tissue- and development-specific manner.

Expression of digestive enzymes and nutrient transporters in the intestine of Eimeria maxima-infected chickens.

Infection with the intestinal protozoa Eimeria causes destruction of intestinal epithelia, resulting in reduced feed efficiency and BW gain. The objective of this study was to investigate the effect of Eimeria maxima infection on the expression of 20 digestive enzymes as well as macro- and micronutrient transporters in the intestine. Expression of the brushborder membrane amino acid transporters EAAT3 (excitatory amino acid transporter 3) and b(o+)AT (Na(+)-independent neutral amino acid transporter) was decreased to 35 to 39% and 20% of control, respectively, in the intestine of E. maxima-infected chickens. Expression of the basolateral amino acid transporter LAT1 and the amino acid transporter ASCT1 was upregulated 17- to 19-fold and 12-fold, respectively, in E. maxima-infected chickens, whereas the zinc transporter was decreased to 20 to 44% of control. In addition, expression of the antimicrobial peptide LEAP-2 (liver-expressed antimicrobial peptide-2) was reduced to 5 to 24% of control. The other 13 digestive enzymes or nutrient transporters examined were unaffected. Together these results suggest a model whereby, upon infection, Eimeria causes a downregulation of LEAP-2. In response, there are changes in expression of the amino acid transporters that would result in a depletion of the energy source (glutamate) and some essential amino acids, which may lead to death of the cell and inhibition of pathogen replication.

Research Note: Junctional adhesion molecule A is expressed in epithelial cells of the crypt and villi whereas junctional adhesion molecule 2 is expressed in vascular cells.

A functional intestinal barrier is essential for a healthy intestine. This barrier includes an apical tight junctional complex between adjacent intestinal epithelial cells. The tight junctions (TJ) are multiprotein junctional complexes that consist of a number of members of the occludin, claudin, zona occludens, and junctional adhesion molecule families. The mRNA expression of junctional adhesin molecule A (JAMA) and junctional adhesion molecule 2 (JAM2) are 2 TJ mRNAs that are often used to assess intestinal barrier integrity. The objective of this study was to use in situ hybridization to identify cells that express JAMA and JAM2 mRNA in the small intestine of chickens. In the jejunum of a 21 d old broiler, JAMA mRNA was highly expressed in the epithelial cells of the villi and crypt. By contrast, JAM2 mRNA was located in the vascular system in the center of the villi and in the lamina propria. These results demonstrate that JAMA and not JAM2 is the appropriate gene to use when assessing TJ between intestinal epithelial cells.

Effects of high incubation temperature on tight junction proteins in the yolk sac and small intestine of embryonic broilers.

During the transition from incubation to hatch, the chicks shift from obtaining nutrients from the yolk sac to the intestine. The yolk sac tissue (YST) and small intestine serve as biological barriers between the yolk or gut contents and the blood circulation. These barriers must maintain structural integrity for optimal nutrient uptake as well as protection from pathogens. The objective of this study was to investigate the effect of high incubation temperature on mRNA abundance of the tight junction (TJ) proteins zona occludens 1 (ZO1), occludin (OCLN), claudin 1 (CLDN1), and junctional adhesion molecules A and 2 (JAMA, JAM2) and the heat shock proteins (HSP70 and HSP90) in the YST and small intestine of embryonic broilers. Broiler eggs were incubated at 37.5°C. On embryonic day 12 (E12), half of the eggs were switched to 39.5°C. YST samples were collected from E7 to day of hatch (DOH), while small intestinal samples were collected from E17 to DOH. The temporal expression of TJ protein mRNA from E7 to DOH at 37.5°C and the effect of incubation temperature from E13 to DOH were analyzed by one-way and two-way ANOVA, respectively and Tukey's test. Significance was set at P < 0.05. The temporal expression pattern of ZO1, OCLN, and CLDN1 mRNA showed a pattern of decreased expression from E7 to E13 followed by an increase to DOH. High incubation temperature caused an upregulation of ZO1 and JAM2 mRNA in the YST and small intestine. Using in situ hybridization, OCLN and JAMA mRNA were detected in the epithelial cells of the YST. In addition, JAMA mRNA was detected in epithelial cells of the small intestine, whereas JAM2 mRNA was detected in the vascular system of the villi and lamina propria. In conclusion, the YST expressed mRNA for TJ proteins and high incubation temperature increased ZO1 and JAM2 mRNA. This suggests that the TJ in the vasculature of the YST and intestine is affected by high incubation temperature.

Temporal expression of avian ß defensin 10 and cathelicidins in the yolk sac tissue of broiler and layer embryos.

The yolk sac is a multifunctional organ, which not only participates in nutrient absorption, but also plays an important role in immune function. The objective of this study was to compare the mRNA abundance of avian ß-defensin 10 (AvBD10) and 3 cathelicidins (CATH1, CATH2, and CATH3) in the yolk sac tissue (YST) of commercial broilers and white egg and brown egg commercial layers. AvBD10 and CATH mRNA abundance was analyzed using two-way ANOVA and Tukey's test, with P < 0.05 being considered significant. AvBD10 and CATH mRNA showed similar temporal expression patterns in the YST of both broiler and layers, with an increase from embryonic day (E) 7 to E9 through E13 followed by a decrease to day of hatch. AvBD10 mRNA showed a breed × age interaction with greater expression in the YST of both layers compared to broilers at E9 and E11. CATH1 mRNA was greater in the YST of brown egg layers than broilers. CATH2 mRNA showed a breed × age interaction, with greater expression in the YST of brown egg layers than broilers at E11. CATH3 mRNA showed no difference in the YST between layers and broilers. Because broilers and brown egg layers are genetically related, these results show that selection for production parameters (broiler vs. layer) and not genetic relatedness (white egg layer vs. brown egg layer and broilers) is the basis for the differences in AvBD10, CATH1, and CATH2 mRNA in the YST of broilers and layers. The yolk-free body weights of broiler embryos were greater than that of both brown and white egg layers from E9 to 17. One possible explanation is that the reduced expression of AvBD10, CATH1 and CATH2 mRNA in the YST of broilers compared to layers at E9 and 11 may be due to faster embryonic growth at the expense of host defense peptide expression in broilers compared to layers.

Gene expression of nutrient transporters and digestive enzymes in the yolk sac membrane and small intestine of the developing embryonic chick.

Chick embryos derive nutrients from the yolk during incubation and transition to intestinal absorption of nutrients posthatch. The uptake of nutrients is mediated by a variety of membrane-bound transporter proteins. The objective of this study was to determine the expression profiles of nutrient transporters and digestive enzymes during incubation in the yolk sac membrane (YSM) and embryonic intestine of egg-laying (Leghorn) and meat-producing (Cobb) chickens derived from 22 to 30 wk (young) and 45 to 50 wk (old) breeder flocks. Transporters examined included the peptide transporter PepT1, the glutamate/aspartate (EAAT3), cationic (CAT-1) and neutral (B0AT) amino acid transporters, and the fructose (GLUT5) and glucose (SGLT1) transporters. Digestive enzymes included aminopeptidase N (APN) and sucrase-isomaltase (SI). Expression of these genes was assessed by real-time PCR using the absolute quantification method in YSM at embryonic day (E) 11, 13, 15, 17, 19, 20, and 21 and intestine at E15, 17, 19, 20, and 21. The PepT1 and APN gene expression in the YSM increased until E15 and then decreased until E21, whereas expression in the intestine increased from E15 to E21. The B0AT showed a similar pattern, with greatest expression in the YSM occurring at E17/E19. The CAT1 and GLUT5 genes showed decreased expression in the YSM and increased expression in the intestine until E17/E19 and then a decrease until E21. Expression of SGLT1 and EAAT3 showed increased gene expression over time in both the intestine and YSM. Expression of SI showed little to no gene expression in the YSM, whereas the intestine exhibited consistently high levels of gene expression. In YSM and intestine, SI expression was greater in Leghorn than Cobb, whereas CAT1 and GLUT5 expression was greater in Cobb than Leghorn. Expression of the APN, CAT1, and SI genes was greater in embryos from young flocks than old flocks in YSM and intestine. These results demonstrate that the YSM expresses many of the digestive enzymes and nutrient transporters typically associated with the intestine and that these genes show tissue- and development-specific patterns of expression.

Expression of the chicken peptide transporter 1 and the peroxisome proliferator-activated receptor α following feed restriction and subsequent refeeding.

The peptide transporter 1 (PepT1) transports di- and tripeptides from the lumen of the small intestine into the enterocyte. Expression of this transporter is affected by numerous factors, including feed restriction. During a fasting state, PepT1 is thought to be regulated by peroxisome proliferator-activated receptor α (PPARα). The objective of this study was to evaluate the effects of a feed restriction-refeeding regimen on expression of chicken PepT1 and PPARα. Ten-day-old broiler chicks were placed on a 24-h feed restriction with 6 birds sampled before and after the restriction. Following feed restriction, the remaining birds were divided into 3 groups: continuously fasted, refed-food withdrawn, and refed ad libitum. The duodenum, jejunum, and ileum were sampled 1, 2, 3, 5, and 7 h post feed restriction. Expression of PepT1 and PPARα increased almost 2-fold post feed restriction (P < 0.002). A significant group × time interaction was observed for PPARα, with the continuously fasted group showing a peak at 29 h postrestriction (P = 0.002). A group × segment interaction was found for both PepT1 (P = 0.002) and PPARα (P = 0.01); within the continuously fasted group, PepT1 expression was greatest in the jejunum (P < 0.001) and ileum (P = 0.01) when compared with the duodenum. No difference was observed between the jejunum and ileum. The PPARα expression was greatest in the jejunum (P = 0.03) when compared with the duodenum, with no difference between the jejunum and ileum or between the duodenum and ileum. The increase in PepT1 expression during a time of reduced feed intake suggests the importance of having transporters ready to scavenge any available luminal nutrients. The concurrent increase in PPARα suggests a possible regulatory role for this receptor in the regulation of PepT1 during feed restriction.

An antimicrobial peptide is downregulated in the small intestine of Eimeria maxima-infected chickens.

Avian coccidiosis is a major disease of poultry caused by the intestinal protozoa Eimeria. Infection leads to reduced feed efficiency and BW gain, resulting in severe economic losses for the poultry industry. Aviagen line A and line B birds show a differential response to Eimeria infection, with line B birds exhibiting higher lesion scores and mortality. The objective of this study was to examine differential intestinal gene expression between 2-wk-old line A and B chicks in response to a challenge with Eimeria maxima. After challenge with 1 × 10(4) oocysts/chick, more than 40% of line A chicks had lesion scores of 0 to 1 (scale of 0 to 4), similar to control chicks. In contrast, all line B chicks challenged at this same dose had lesion scores of 2 to 4. Total RNA was extracted from the jejunum of control and challenged chicks from both lines A and B. Microarray analysis revealed that liver-expressed antimicrobial peptide 2 (LEAP-2), a component of the innate immune system, was downregulated 20-fold in line A challenged chicks with lesion scores of 2 to 4 compared with line A control chicks, and was downregulated 11- to 71-fold in line B challenged chicks with lesion scores of 2 to 4 compared with line B control chicks. Liver-expressed antimicrobial peptide 2 was downregulated less than 2-fold in line A challenged chicks with lesion scores of 1 compared with line A control chicks, indicating that these chicks were similar to control chicks in their expression level of LEAP-2. Other genes (cytochrome P450, heat shock protein 25, keratin 19, and amino acid transporter ASCT1) showed different patterns of over- or underexpression. The expression of LEAP-2 was verified using real-time PCR, revealing a correlation between lesion score and magnitude of LEAP-2 downregulation for both line A and line B chicks. Thus, LEAP-2 may serve as a useful marker for identification of chickens resistant to E. maxima infection and potentially other Eimeria spp.

Centennial Review: The chicken yolk sac is a multifunctional organ.

The yolk sac (YS) consists of the yolk, which supplies nutrients, and the YS tissue, which surrounds the yolk and provides essential metabolic functions for the developing embryo. The YS tissue is derived from the midgut of the embryo and consists of a layer of endodermal epithelial cells (EEC) in contact with the yolk contents, a mesodermal layer that contains the vascular system and an outer ectodermal layer. The YS tissue is a multifunctional organ that provides essential functions such as host immunity, nutrient uptake, carbohydrate and lipid metabolism, and erythropoiesis. The YS tissue plays a role in immunity by the transport of maternal antibodies in the yolk to the embryonic circulation that feeds the developing embryo. In addition, the YS tissue expresses high mRNA levels of the host defense peptide, avian ß-defensin 10 during mid embryogenesis. Owing to its origin, the YS EEC share some functional properties with intestinal epithelial cells such as expression of transporters for amino acids, peptides, monosaccharides, fatty acids, and minerals. The YS tissue stores glycogen and expresses enzymes for glycogen synthesis and breakdown and glucogenesis. This carbohydrate metabolism may play an important role in the hatching process. The mesodermal layer of the YS tissue is the site for erythropoiesis and provides erythrocytes before the maturation of the bone marrow. Other functions of the YS tissue involve synthesis of plasma proteins, lipid transport and cholesterol metabolism, and synthesis of thyroxine. Thus, the YS is an essential organ for the growth, development, and health of the developing embryo. This review will provide an overview of the studies that have investigated the functionalities of the YS tissue at the cellular and molecular levels with a focus on chickens.

Research Note: Intestinal morphology and gene expression changes in broilers supplemented with lysolecithin.

Lysolecithin is used as a feed additive to aid fat digestion and absorption in broiler chickens. Previous research has shown that dietary fat source influences how broilers respond to lysolecithin supplementation. Therefore, the objective of this study was to investigate the effect of lysolecithin on a diet formulated with soybean oil on jejunum morphology and expression of selected genes in broiler chickens. Male Cobb 500 chickens were fed a Control diet or the Control diet supplemented with lysolecithin (TRT) from day of hatch to day 28. Jejunal samples were collected at day 10 for morphological and gene expression analysis. Feeding the TRT diet did not affect BW, villus height (VH), crypt depth (CD) or VH/CD ratio compared to Control fed chickens. Differential gene expression in the jejunum was analyzed using a custom microarray. Using a t test, 36 genes were found to be upregulated in TRT fed chickens compared to chickens fed the Control diet. The two most upregulated genes were carbonic anhydrase VII and interleukin 8-like 2, which are associated with healthy intestines. In summary, lysolecithin supplementation in a diet formulated with soybean oil caused no morphological changes but upregulated a number of genes in the jejunum.

Dietary protein composition influences abundance of peptide and amino acid transporter messenger ribonucleic acid in the small intestine of 2 lines of broiler chicks.

This study evaluated the effect of dietary protein composition on mRNA abundance of a peptide transporter (peptide transporter 1, PepT1), amino acid (AA) transporters [Na(+)-independent cationic and zwitterionic AA transporter (b(o,+)AT), excitatory AA transporter 3 (EAAT3), Na(+)-independent cationic and Na(+)-dependent neutral AA transporter 2 (y(+)LAT2), L-type AA transporter 1 (LAT1), and cationic AA transporter 1 (CAT1)], and a digestive enzyme (aminopeptidase N) in 2 lines (A and B) of broilers that differentially express PepT1 mRNA (line B > line A). From d 8 to 15 posthatch, birds were fed 1 of 3 diets. Protein sources included whey protein concentrate, a whey partial hydrolysate (WPH), or a mixture of free AA (AA) identical to the composition of whey. Quantities of mRNA were assayed by real-time PCR in the small intestine of males at d 8, 9, 11, 13, and 15. For all genes except LAT1, abundance of mRNA was greatest in line B birds that consumed the WPH diet (P < 0.006). When mRNA abundance was normalized to beta-actin quantities, this effect disappeared, demonstrating a generalized effect on gene expression in line B birds that consumed the hydrolysate. There was a greater villus height:crypt depth ratio (P < 0.05) in line B birds fed the WPH diet as compared with line A. In conclusion, line B birds, which express greater PepT1, displayed enhanced intestinal mucosal absorptive surface area and differential regulation of PepT1, AA transporters, and aminopeptidase N in response to dietary protein composition.

Delayed access to feed affects broiler small intestinal morphology and goblet cell ontogeny.

Broilers are often deprived of feed and water for up to 48 h after hatch. This delayed access to feed (DAF) can inhibit small intestine development. The objective of this study was to determine the effects of DAF on small intestinal morphology, mRNA abundance of the goblet cell marker Muc2 and absorptive cell marker PepT1, and the distribution of goblet cells in young broilers. Cobb 500 chicks, hatching within a 12-h window, were randomly allocated into 3 groups: control with no feed delay (ND), 24-h feed delay (DAF24), and 36-h feed delay (DAF36). Morphology, gene expression, and in situ hybridization analyses were conducted on the duodenum, jejunum, and ileum at 0, 24, 36, 72, 120, and 168 h after hatch. Statistical analysis was performed using a t test for ND and DAF24 at 24 h. A 2-way ANOVA and Tukey's HSD test (P < 0.05) were used for ND, DAF24, and DAF36 from 36 h. At 24 to 36 h, DAF decreased the ratio of villus height/crypt depth (VH/CD) in the duodenum but increased VH/CD in the ileum due to changes in CD, whereas at 72 h, DAF decreased VH/CD due to a decrease in VH. The mRNA abundance of PepT1 was upregulated, while Muc2 mRNA was downregulated in DAF chicks. Cells expressing Muc2 mRNA were present along the villi and in the crypts. The ratio of the number of goblet cells found in the upper half to the lower half of the villus was greater in DAF chicks than in ND chicks, suggesting that DAF affected the appearance of new goblet cells. The number of Muc2 mRNA-expressing cells in the crypt, however, was generally not affected by DAF. In conclusion, DAF transiently affected small intestinal morphology, upregulated PepT1 mRNA, downregulated Muc2 mRNA, and changed the distribution of goblet cells in the villi. By 168 h, however, these parameters were not different between ND, DAF24, and DAF36 chicks.

Changes with age in density of goblet cells in the small intestine of broiler chicks.

Goblet cells secrete mucin 2 (Muc2), which is a major component of the mucus that lines the intestinal tract and creates a protective barrier between pathogens and the intestinal epithelial cells and thus are important for chick health. The objectives of this study were to determine the age-specific and intestinal segment-specific expression of Muc2 mRNA and changes in the number of goblet cells from late embryogenesis to early after hatch. Small intestinal samples from the duodenum, jejunum, and ileum were collected from Cobb 500 broilers at embryonic day 19 (e19), day of hatch (doh), and day 2 and 4 after hatch. Cells expressing Muc2 mRNA and mucin glycoprotein were detected by in situ hybridization or alcian blue and periodic acid-Schiff staining, respectively. Along the villi, there were many more cells expressing Muc2 mRNA than those stained for mucin glycoprotein. In the crypt, cells expressing Muc2 mRNA did not stain for mucin glycoprotein. There was an increase in the density of goblet cells in the villi and Muc2 mRNA expressing cells in the crypts of the jejunum and ileum from e19 to doh and day 2 to day 4, with no change between doh and day 2. In contrast, in the duodenum, the density of goblet cells in the villi and Muc2 mRNA expressing cells in the crypts remained constant from e19 to day 4. At day 4, the villi in the ileum had a greater density of goblet cells than the duodenum. In the crypt, the ileum had a greater density of Muc2 mRNA expressing cells than the duodenum at doh, and the ileum and jejunum both had greater densities of Muc2 mRNA expressing cells than the duodenum at day 4. These results indicate that the population of goblet cells has reached a steady state by doh in the duodenum, whereas in the jejunum and ileum, a steady-state population was not reached until after hatch.