Expression and localisation of calbindin D28k in all intestinal segments of the laying hen

Heat stress and poultry production: a comprehensive review

The impact of global warming on poultry production has gained significant attention over the years. However, our current knowledge and understanding of the mechanisms through which heat stress (HS) resulting from global warming affects the welfare, behavior, immune response, production performance, and even transgenerational effects in poultry are still incomplete. Further research is needed to delve deeper into these mechanisms to gain a comprehensive understanding. Numerous studies have investigated various biomarkers of stress in poultry, aiming to identify reliable markers that can accurately assess the physiological status and well-being of birds. However, there is a significant amount of variation and inconsistency in the results reported across different studies. This inconsistency highlights the need for more standardized methods and assays and a clearer understanding of the factors that influence these biomarkers in poultry. This review article specifically focuses on 3 main aspects: 1) the neuroendocrine and behavioral responses of poultry to HS, 2) the biomarkers of HS and 3) the impact of HS on poultry production that have been studied in poultry. By examining the neuroendocrine and behavioral changes exhibited by poultry under HS, we aim to gain insights into the physiological impact of elevated temperatures in poultry.

Use of lactulose as a prebiotic in laying hens: its effect on growth, egg production, egg quality, blood biochemistry, digestive enzymes, gene expression and intestinal morphology

BACKGROUND

The rising popularity of eggs as an alternative source of protein to meat has led to significant increase in egg consumption over the past decade. To meet the increasing demand for eggs, poultry farmers have used antibiotics to treat infections and, to some extent, promote growth and egg production in raising layer. However, the emergence and global spread of antibiotic resistant bacteria has now necessitated antibiotic-free poultry farming. As alternatives to antibiotics, prebiotics are feed additives that can be used to improve the growth and laying performance of poultry which positively impacts their performance and general health. In this study we evaluated the effect of lactulose, formulated as Vetelact, on body weight, egg production, egg quality, blood biochemical parameters and expression of genes associated with reproductive performance in laying hens.

RESULTS

Vetelact supplementation improved egg weight, egg production as well as egg quality. Following Vetalact supplementation, the levels of total bilirubin, total protein, globulin and phosphorus were increased, while the activities of alkaline phosphatase and lipase enzymes were increased compared to control. Vetelact at 0.10 ml/kg body weight upregulated OCX-36, OVAL, CALB1, OC-116, OCX-32 and IL8 transcripts while downregulating the transcription of Gal-10, PENK and AvBD9. At this optimal inclusion rate of Vetalect, histomorphologic analyses of intestinal tissue showed increased villi length with more goblet cell distribution and obvious mucus covering a surface, increase in the depth of intestinal crypts produce digestive enzymes, as well as more developed muscle layer that promote improved nutrient absorption.

CONCLUSION

Vetelact at a dose of 0.10 ml/ kg body weight was effective in improving productive performance of laying hens. Adding lactulose (0.10 ml/ kg body weight) to layer diet is recommended to promote growth and improve egg laying performance in antibiotics-free poultry production.

Effects of rearing systems on the eggshell quality, bone parameters and expression of genes related to bone remodeling in aged laying hens

Public concerns regarding animal welfare are changing the selection of rearing systems in laying hens. This study investigated the effects of rearing systems on eggshell quality, bone parameters and relative expression levels of genes related to bone remodeling in aged laying hens. A total of 2,952 55-day-old Jing Tint Six pullets were randomly assigned to place in the conventional caging system (CCS) or aviary system (AVS) and kept until 95 weeks of age. The AVS group delayed the decrease of eggshell quality and alleviated the symptoms of osteoporosis in the humerus rather than in the femur. Eggshell breaking strength, thickness, weight, weight ratio, stiffness and fracture toughness were decreased linearly with age (from 55 to 95 weeks of age, p < 0.05). The AVS group had higher eggshell breaking strength, stiffness and fracture toughness than the CCS group (p < 0.05). Higher total calcium and phosphorus per egg were presented in the AVS group at 95 weeks of age (p < 0.05). At 95 weeks of age, the AVS group had a humerus with higher weight, volume, length, midpoint perimeter, cortical index, fat-free dry weight, ash content, total calcium per bone, total phosphorus per bone, average bone mineral density, strength, stiffness and work to fracture compared to the CCS group (p < 0.05). Such differences did not appear in the femur. The relative expression levels of alkaline phosphatase (ALP) and osteocalcin (OCN) genes in the femur and hormone receptors (vitamin D receptor (VDR), estrogen receptor alpha (ERα) and fibroblast growth factor 23 (FGF23)) genes in the humerus were significantly upregulated (p < 0.05) in the AVS group. The level of tartrate-resistant acid phosphatase (TRAP) transcripts was also increased (p < 0.05) in the femur of the AVS group. Overall, compared with the CCS, the AVS alleviated the deterioration of eggshell and bone qualities of aged laying hens, which may be related to the changes in the expression of genes associated with bone remodeling.

Dietary calcium levels regulate calcium transporter gene expression levels in the small intestine of broiler chickens

1. This study investigated the effect of dietary calcium (Ca) levels on growth performance, bone development and Ca transporter gene expression levels in the small intestine of broiler chickens.2. On the day of hatch, 350, Ross 308 male broilers were randomly allotted to one of five treatments with five replicate pens each and 14 birds per pen. Dietary Ca levels in feed were 5.0, 7.0, 9.0, 11.0 and 13.0 g/kg, in which 9.0 g/kg was in the control diet. All diets contained 4.5 g/kg non-phytate phosphorus (NPP).3. The increase in dietary Ca levels from 5.0 to 13.0 g/kg did not affect the growth performance of 1- to 18-day-old broilers (P > 0.05).4. Increasing the Ca levels linearly increased the ash weight and the contents of ash, Ca and phosphorus (P) in the tibia of broilers at 18 days of age (P < 0.05). The contents of ash, Ca and P in broilers fed with 9.0 g/kg Ca were higher than those in birds fed with 5.0 g/kg Ca (P < 0.05).5. Increasing the Ca levels linearly decreased mRNA expression levels of the Ca-binding protein 28-kDa (CaBP-D28k), plasma membrane Ca-transporting ATPase 1b (PMCAlb), sodium (Na)/Ca exchanger 1 (NCX1), nuclear vitamin D receptor (nVDR) and membrane vitamin D receptor (mVDR) in the duodenum of broilers at 18 d of age (P < 0.05). Similar results were seen in the jejunum and ileum. Broilers fed 9.0-13.0 g/kg Ca in feed had lower mRNA expression levels of CaBP-D28k and PMCAlb in the small intestine than birds fed 5.0 g/kg Ca in feed (P < 0.05).6. The data indicated that low levels of dietary Ca stimulated its transporter gene transcription and promoted absorption, but high levels of Ca inhibited transporter gene expression and prevented excessive absorption in the small intestine of broiler chickens.

Methionine supplementing effects on intestine, liver and uterus morphology, and on positivity and expression of Calbindin-D28k and TRPV6 epithelial calcium carriers in laying quail in thermoneutral conditions and under thermal stress

This study aimed to provide the performance, localization and expression of the epithelial calcium transporter channels Calbindin-D28k (Calb) and TRPV6, and of the morphology of the digestive and reproductive system of laying quail under heat stress (HS), and with methionine supplementation (MS). This study characterized the positivity (immunohistochemistry) and expression (real-time PCR) of calcium channels in the kidneys, intestine and uterus of 504 laying quails under different MS (100, 110 and 120%) and temperatures (20, 24, 28 and 32°C). The animals under HS (32°C) had lower villus height, villus:crypt ratio, and goblet cell index in the duodenum and jejunum, fewer secondary and tertiary uterine folds, smaller hepatic steatosis, and increased number of distal convoluted renal tubules (CT) positive to Calb, and increased positivity in proximal CTs. Deleterious effects of HS were minimized with MS for: duodenal crypts, number of goblet cells of the jejunum, number of uterine folds, decreased Calb positivity in intestines and kidney, increased positivity of Calb in the uterus and increased TRPV6 gene expression in the kidney (P≤0.05). Epithelial calcium transporters were altered due to less need for calcium absorption and reabsorption due to more calcium available with the MS, increasing egg production in HS and quality in termoneutrality (P≤0.05). MS further increased intestinal villus absorption area and height, increased steatosis, decreased Calb positivity in the intestine and kidney, increased uterine positivity of Calb, and increase Calb and TRPV6 expression in the kidney (P≤0.001) under thermoneutrality. It was concluded that the use of MS (120%) is justifiable in order to partially reverse the deleterious effects of HS on the production, in the epithelial calcium carriers, and in the digestory and reproductive morphology of laying quail.

1,25-Dihydroxycholecalciferol Improved the Growth Performance and Upregulated the Calcium Transporter Gene Expression Levels in the Small Intestine of Broiler Chickens

1,25-Dihydroxycholecalciferol (1,25-(OH)₂-D₃) is the final active product of vitamin D. This study aimed to investigate the effects of 1,25-(OH)₂-D₃ on growth performance, bone development, and calcium (Ca) transporter gene expression levels in the small intestine of broiler chickens. On the day of hatching, 140 female Ross 308 broilers were randomly allotted into two treatments with five replicates (14 birds per replicate). Two levels of 1,25-(OH)₂-D₃ (0 and 1.25 µg/kg) were added to the basal diet without vitamin D. Results showed that the addition of 1.25 µg/kg 1,25-(OH)₂-D₃ increased the average daily feed intake and the average daily gain and decreased the feed conversion ratio and mortality in 1- to 19-day-old broiler chickens compared with the basal diet without vitamin D (P<0.05). 1,25-(OH)₂-D₃ also enhanced the length, weight, ash weight, and the percentage contents of ash, Ca, and P in the tibia and femur of broilers (P<0.05). The mRNA expression levels of the Ca-binding protein (CaBP-D28k) in the duodenum, jejunum, and ileum of 19-day-old broilers increased to 88.1-, 109.1-, and 2.7-fold, respectively, after adding 1,25-(OH)₂-D₃ (P<0.05). The mRNA expression levels of the plasma membrane Ca ATPase 1b (PMCAlb) in the duodenum and the sodium (Na)/ Ca exchanger 1 (NCX1) in the duodenum and the jejunum were also enhanced to 1.57-2.86 times with the addition of 1,25-(OH)₂-D₃ (P<0.05). In contrast, the mRNA expression levels of PMCA1b and NCX1 in the ileum and that of vitamin D receptor (VDR) in the small intestine were not affected by 1,25-(OH)₂-D₃ (P>0.05). These data indicate that 1,25-(OH)₂-D₃ upregulated Ca transporter gene transcription and promoted Ca²⁺ absorption in the small intestine, especially in the proximal intestine (duodenum and jejunum), thereby improving growth performance and bone mineralization in broiler chickens.

Relationship between Bone Stability and Egg Production in Genetically Divergent Chicken Layer Lines

Impaired animal welfare due to skeletal disorders is likely one of the greatest issues currently facing the egg production industry. Reduced bone stability in laying hens is frequently attributed to long-term selection for increased egg production. The present study sought to analyse the relationship between bone stability traits and egg production. The study comprised four purebred layer lines, differing in their phylogenetic origin and performance level, providing extended insight into the phenotypic variability in bone characteristics in laying hens. Data collection included basic production parameters, bone morphometry, bone mineral density (BMD) and bone breaking strength (BBS) of the tibiotarsus and humerus. Using a multifactorial model and regression analyses, BMD proved to be of outstanding importance for bone stability. Only for the tibiotarsus were morphometric parameters and the bone weight associated with BBS. Within the chicken lines, no effect of total eggshell production on BBS or BMD could be detected, suggesting that a high egg yield itself is not necessarily a risk for poor bone health. Considering the complexity of osteoporosis, the estimated genetic parameters confirmed the importance of genetics in addressing the challenge of improving bone strength in layers.

Effects of dietary supplementation with Clostridium butyricum on laying performance, egg quality, serum parameters, and cecal microflora of laying hens in the late phase of production

This experiment was conducted to evaluate the effects of dietary supplementation with Clostridium butyricum on laying performance, egg quality, serum parameters, and cecal microflora of laying hens in the late phase of production. Jinghong-1 strain laying hens (n = 960; 48 wk of age) were randomly allocated to 5 treatment groups with 6 replicates of 32 hens. Hens were fed with basal diet (control) and basal diet supplemented with 2.5 × 104 (CB1), 5 × 104 (CB2), 1 × 105 (CB3), and 2 × 105 (CB4) cfu/g C. butyricum for 10 wk. The results showed that egg production, egg mass, and eggshell strength increased quadratically as supplemental C. butyricum increased, and these responses were maximized in the CB2 group (P < 0.05). Compared with the control group, the addition of C. butyricum resulted in quadratic effects on serum total protein, uric acid, calcium, complement component C3 and catalase concentrations, and these responses were maximized or minimized in the CB2 group (P < 0.05). Linear and quadratic increases were observed in serum IgM, total superoxide dismutase, and glutathione peroxidase concentrations, and these responses were maximized in CB2 or CB3 group (P < 0.05). The addition of C. butyricum in the CB2 group resulted in linearly increasing levels of serum IgG concentration as compared with the control group (P < 0.05). Spleen index increased (P < 0.05) in the CB2 group. Hens fed with C. butyricum reduced (P > 0.05) the population of E. coli, while Bifidobacterium counts increased quadratically and maximized in the CB2 group (P < 0.05). In conclusion, the results indicated that dietary supplementation with C. butyricum (5 × 104 or 1 × 105 cfu/g) could improve laying performance and egg quality by promoting immune function, enhancing antioxidative capacity, and benefiting the cecal microflora of laying hens in the late phase of production.

Non-linear increase of vitamin D content in eggs from chicks treated with increasing exposure times of ultraviolet light

Vitamin D fortified food can help to reduce the prevalence for vitamin D deficiency. Previous data provided evidence that eggs from hens exposed to ultraviolet (UV) light contain large quantities of vitamin D. In the current study, we assessed the efficacy of vitamin D enrichment in eggs upon increasing daily UVB exposure times. We further addressed the question whether extended UVB irradiation affects the skin content of 7-dehydrocholesterol. To this end, 35 hens were assigned to 7 groups of 5 animals each and were exposed to UVB light (76μW/cm(2)) for 0, 15, 30, 60, 120, 180 and 300min per day, respectively. Eggs from the treatment groups were collected at baseline and after 2, 3 and 4 weeks of treatment, respectively. Skin samples were gained at the end of 4 weeks. Vitamin D metabolites were quantified by liquid chromatography-tandem mass spectrometry. The contents of vitamin D3 and 25(OH)D3 in egg yolk raised non-linear in response to increasing daily UVB exposure times. The vitamin D3 content did not reach a clear-cut plateau within the chosen UVB treatment times. A daily UVB exposure time of 300min resulted in vitamin D3 contents of 28.6μg/100g egg yolk dry matter. In contrast to vitamin D3, the 25(OH)D3 content in the egg yolk achieved a maximum upon an UVB irradiation time of 60min/d. The cutaneous 7-dehydrocholesterol contents were not altered in response to the chosen UVB irradiation times. In conclusion, the data show a distinct non-linear dose-response relationship of UVB exposure times on the total vitamin D content in eggs. This article is part of a special issue entitled '17th Vitamin D Workshop'.

Localisation and expression of TRPV6 in all intestinal segments and kidney of laying hens

1. The aim of this study was to investigate the localisation and expression of the epithelial Ca2+ channel TRPV6 (transient receptor potential vanilloid channel type 6) in different intestinal segments and kidney of laying hens during peak lay. 2. Immunohistochemical analysis of the intestine indicated that TRPV6 was localised to the brush-border membranes of the duodenum, jejunum, ileum, caecum, and rectum. Expression was weaker in the rectum, and little or no expression was found in crypt and goblet cells. In addition, TRPV6 mRNA was quantified amongst different intestinal segments, and expression was highest in the duodenum and jejunum. Furthermore, Western blotting indicated that the duodenum expressed the greatest amount of TRPV6 and the rectum the least with the other segments expressing intermediate levels. 3. In the kidney, distinct immunopositive staining for TRPV6 was detected at the apical domain of the distal convoluted tubules (DCT) and medullary connecting tubules (CNT). Interestingly, distribution of TRPV6 extended to the proximal convoluted tubules (PCT). Furthermore, the kidney expressed lower TRPV6 mRNA and protein levels compared with that in the duodenum. 4. In conclusion, the epithelial Ca2+ channel TRPV6 is strongly expressed in the apical cells of the entire intestine and the renal tubules, suggesting that active Ca2+ transcellular transport plays a crucial role in dietary calcium (re)absorption in laying hens.

Calcium transport in strongly calcifying laying birds: mechanisms and regulation

Birds that lay long clutches (series of eggs laid sequentially before a "pause day"), among them the high-producing, strongly-calcifying Gallus gallus domesticus (domestic hen) and Coturnix coturnix japonica (Japanese quail), transfer about 10% of their total body calcium daily. They appear, therefore, to be the most efficient calcium-transporters among vertebrates. Such intensive transport imposes severe demands on ionic calcium (Ca2+) homeostasis, and activates at least two extremely effective mechanisms for Ca2+ transfer from food and bone to the eggshell. This review focuses on the development, action and regulation of the mechanisms associated with paracellular and transcellular Ca2+ transport in the intestine and the eggshell gland (ESG); it also considers some of the proteins (calbindin, Ca2+ATPase, Na+/Ca2+ exchange, epithelial calcium channels (TRPVs), osteopontin and carbonic anhydrase (CA) associated with this phenomenon. Calbindins are discussed in some detail, as they appear to be a major component of the transcellular transport system, and as only they have been studied extensively in birds. The review aims to gather old and new knowledge, which could form a conceptual basis, albeit not a completely accepted one, for our understanding of the mechanisms associated with this phenomenon. In the intestine, the transcellular pathway appears to compensate for low Ca2+ intake, but in birds fed adequate calcium the major drive for calcium absorption remains the electrochemical potential difference (ECPD) that facilitates paracellular transport. However, the mechanisms involved in Ca2+ transport into the ESG lumen are not yet established. In the ESG, the presence of Ca2+-ATPase and calbindin--two components of the transcellular transport pathway--and the apparently uphill transport of Ca2+ support the idea that Ca2+ is transported via the transcellular pathway. However, the positive (plasma with respect to mucosa) electrical potential difference (EPD) in the ESG, among other findings, indicates that there may be major alternative or complementary paracellular passive transport pathways. The available evidence hints that the flow from the gut to the ESG, which occurs during a relatively short period (11 to 14 h out the 24- to 25.5-h egg cycle), is primarily driven by carbonic anhydrase (CA) activity in the ESG, which results in high HCO3(-) content that, in turn, "sucks out" Ca2+ from the intestinal lumen via the blood and ESG cells, and deposits it in the shell crystals. The increased CA activity appears to be dependent on energy input, whereas it seems most likely that the Ca2+ movement is secondary, that it utilizes passive paracellular routes that fluctuate in accordance with the appearance of the energy-dependent CA activity, and that the level of Ca2+ movement mimics that of the CA activity. The on-off signals for the overall phenomenon have not yet been identified. They appear to be associated with the circadian cycle of gonadal hormones, coupled with the egg cycle: it is most likely that progesterone acts as the "off" signal, and that the "on" signal is provided by the combined effect of an as-yet undefined endocrine factor associated with ovulation and with the mechanical strain that results from "egg white" formation and "plumping". This strain may initially trigger the formation of the mammillae and the seeding of shell calcium crystals in the isthmus, and thereafter initiate the formation of the shell in the ESG.