Identify Candidate Genes Associated with the Weight and Egg Quality Traits in Wenshui Green Shell-Laying Chickens by the Copy Number Variation-Based Genome-Wide Association Study.

Copy number variation (CNV), as an essential source of genetic variation, can have an impact on gene expression, genetic diversity, disease susceptibility, and species evolution in animals. To better understand the weight and egg quality traits of chickens, this paper aimed to detect CNVs in Wenshui green shell-laying chickens and conduct a copy number variation regions (CNVRs)-based genome-wide association study (GWAS) to identify variants and candidate genes associated with their weight and egg quality traits to support related breeding efforts. In our paper, we identified 11,035 CNVRs in Wenshui green shell-laying chickens, which collectively spanned a length of 13.1 Mb, representing approximately 1.4% of its autosomal genome. Out of these CNVRs, there were 10,446 loss types, 491 gain types, and 98 mixed types. Notably, two CNVRs showed significant correlations with egg quality, while four CNVRs exhibited significant associations with body weight. These significant CNVRs are located on chromosome 4. Further analysis identified potential candidate genes that influence weight and egg quality traits, including FAM184B, MED28, LAP3, ATOH8, ST3GAL5, LDB2, and SORCS2. In this paper, the CNV map of the Wenshui green shell-laying chicken genome was constructed for the first time through population genotyping. Additionally, CNVRs can be employed as molecular markers to genetically improve chickens' weight and egg quality traits.

Subchronic toxicity of oral deltamethrin in laying chickens.

Pyrethroid pesticides, with low toxicity to birds and mammals and short persistence in the environment, are widely used now. With the development of intensive poultry farming, pesticide application leads to residues in poultry products and pollution in ecological environment. The aim of the present study was to examine deltamethrin subchronic toxicity in laying chickens. One hundred and twelve laying chickens were randomly assigned to 14 groups including 13 groups medicated with deltamethrin (n = 8) and one unmedicated group used as control (n = 8). Tissue samples were collected during and after administration for weighing and histopathological analysis. A single dose of deltamethrin (20 mg·kg-1·BW·d) was administered orally to laying chickens for 14 days. The results showed that deltamethrin has no significant effect on the relative organ weight of laying chickens (p > 0.05). The activities of aspartate aminotransferase and cholinesterase in the plasma gradually decreased over time in the medicated group (p < 0.05). Plasma concentrations of urea nitrogen, uric acid, cholesterol, triglycerides, and creatinine significantly increased during treatment (p < 0.05), and significant liver damage and loss of intestinal villous epithelium were observed. The intestinal wall thickness, villus height, and crypt depth of laying chickens were altered by deltamethrin treatment. During treatment was withdrawn, the intestinal repair was more extensive than the liver repair.

Eimeria infections among commercial laying chickens in Nigeria: the prevalence and clinico-histopathological changes.

Coccidiosis is known to affect a wide range of animals including chickens. This study was designed to determine the nation-wide prevalence and clinico-histopathological changes associated with Eimeria infections in commercial laying birds in Nigeria. One Thousand eight hundred and forty-three (1843) commercial laying chickens from 28 states and the Federal Capital Territory (FCT) of Nigeria, between 2007 and 2016 were examined for the presence of Eimeria parasites and for clinicopathological lesions. Simple flotation and the McMaster techniques were used to confirm the presence of Eimeria oocysts and estimate the oocyst load. Positive samples were sporulated for the purpose of species differentiation. Gross and histopathology were carried out accordingly. Two hundred and seven (207) faecal samples/carcasses were positive for Eimeria infections (11.23%; 95% CI = 9.87-12.75). Eimeria tenella and E. necatrix were the most prevalent species. The highest mean oocyst per gram (OPG) was recorded in E. acervulina (5260.87 (± 1838.35)). The prevalence of Eimeria infections in commercial laying birds within the states ranged between 4.4% (Kaduna State), and 33% (Ebonyi and Lagos States), and 21.1% in FCT. There was a higher prevalence of Eimeria infections in commercial laying birds that are less than 1 year compared to those above a year. Eimeria infections was 2.19 times more likely to occur during the wet season compared to the dry season (95% CI = 1.59-3.06; χ2 = 23.29; P = < 0.01). One hundred and eighty-five (185) carcasses showed moderate petechiae to ecchymotic intestinal/caecal mucosa, while 22 carcasses showed severe petechiae to ecchymotic intestinal/caecal mucosa with bloody intestinal lumen. This study appears to be the first nation-wide study on the prevalence and clinico-histopathological changes associated with Eimeria infections in commercial laying chickens in Nigeria.

In vivo typing of Escherichia coli obtained from laying chickens with the E. coli peritonitis syndrome.

Fourteen genetically different chicken Escherichia coli strains were biotyped in hens to examine if any E. coli strain at high dose can induce the E. coli peritonitis syndrome (EPS). Moreover, biotyping was performed in embryos and the median lethal dose (LD50) of three strains was determined in hens. Nine strains were obtained from femur marrow and one strain from caecum of hens that had died from EPS. One strain originated from the inflamed pericardium of a broiler and three strains from the cloaca of specified pathogen-free (SPF) broiler breeders. Strains were inoculated intratracheally into separate groups of 32 productive SPF White Leghorn (WL) hens at a dose of 7.8-9.2 log10 colony forming units (CFU) per hen and into the allantoic cavity of separate groups of 20 SPF WL embryos incubated during 14 days in a dose of 4.2-4.6 log10 CFU per embryo. The embryo test was replicated. Bone marrow and pericardium strains induced EPS, the other strains did not. Based on mortality in hens, EPS-inducing strains could be classified as very virulent (59-100% mortality), moderately virulent (38% mortality) and low virulent (6% mortality). In productive SPF WL hens, the LD50 of three very virulent strains ranged from <2.7 to 5.3 log10 CFU. Virulent and avirulent strains killed 60-95% and 0-30% of embryos, respectively. The embryo lethality test, which showed good reproducibility, did not discriminate within virulent strains, but can nevertheless be considered as a useful alternative for biotyping E. coli in productive hens.RESEARCH HIGHLIGHTSEven at high doses, no E. coli strain could induce EPS.Substantial differences in virulence exist within very virulent E. coli strains.The embryo lethality test is a useful alternative for biotyping E. coli in laying hens.Broiler colibacillosis may represent a source of EPS strains for layers and vice versa.

Triple La Sota re-vaccinations can protect laying chickens for 3 months against drop in egg production caused by velogenic viscerotropic Newcastle disease virus infection.

One hundred and ten Isa Brown layers were vaccinated with La Sota, once at point of lay at 18 weeks and three times at peak of lay which occurred at 27-29 weeks of age. Thereafter, they were weekly monitored for haemagglutination inhibition (HI) antibody decline. The first batch A of the layers were challenged with velogenic viscerotropic Newcastle disease (vvND) virus (vvNDV) on day 24 post-vaccination (PV), when the geometric mean titre (GMT) was 84.4, batch B were challenged on day 48 PV at GMT of 42.2, while batch C were challenged on day 97 PV at GMT of 21.1. The individual chicken HI antibody titres of the 10 layers in batch C at the day of challenge were: 7 layers had HI titres of 16, 2 layers had HI titres of 32 and 1 layer had HI titres of 64. Each challenge in the three batches produced no clinical signs including drop in egg production. But there was initial swelling of the spleen followed by atrophy with high antibody responses. The virus was recovered in all the cloacal swabs on days 3-9 post-challenge (PC) at low titres. On days 145 PV and 48, post-Batch C challenge the remaining hyperimmunized unchallenged layers demonstrated a drop in total % egg production (p < .05) and changes in egg quality. The HI GMT was 256. The virus was recovered in all the cloacal swabs on days 3-9 following appearance of clinical signs. There was no mortality in the experiment. Based on the above observations, it is concluded that triple La Sota re-vaccination can protect layers against a drop in egg production in areas where vvNDV infection is enzootic.

Association of Beta2-Positive Clostridium perfringens Type A With Focal Duodenal Necrosis in Egg-Laying Chickens in the United States.

Focal duodenal necrosis (FDN) is a poorly understood intestinal disease of egg layers, and has been associated with drops in egg production and decreased egg weights. The etiology of this disease is still unknown, but the condition has been associated with Clostridium colinum and Clostridium perfringens. In order to investigate the etiology, duodenal samples were taken from hens with FDN. The hens originated from table egg layer farms in three states. The samples were examined by histopathology, bacteriology, and immunohistochemistry. Macroscopically, all samples contained focal to multifocal, variably sized, reddened or brownish gray areas of mucosal erosion. Histopathology revealed mild to severe heterophilic and lymphoplasmacytic enteritis with loss of enterocytes at the villous tips, luminal fibrinonecrotic exudate, and variable numbers of Gram-positive and Gram-negative rod-shaped bacteria within the lesions in 16/30 samples. Clostridium perfringens was isolated by anaerobic bacteriology from 4/13 samples that had characteristic microscopic lesions of FDN. Polymerase chain reaction (PCR) revealed that all four isolates were Type A C. perfringens, positive for beta2 gene and negative for necrotic enteritis toxin B and enterotoxin genes. PCR for Clostridium colinum applied to DNA extracted from frozen intestinal samples yielded negative results in 14/14 duodenal samples. Immunohistochemistry (IHC) for 7C. perfringens, alpha and beta2 toxins stained a few to numerous long rod-shaped bacteria present in the lesions. IHC for alpha and beta2 toxins also stained enterocytes at the villous tips, inflammatory cells in the lamina propria, as well as degenerated and sloughed enterocytes present within the luminal exudate. These findings suggest that C. perfringens may play a role in the development of FDN. Experimental challenge studies with these isolates still need to be performed in order to reproduce the disease and fulfill Koch's postulates.

Cutaneous mucinosis in a strain of brown-egg laying chickens.

Cutaneous mucinosis is a cutaneous disorder described in humans, dogs, and rarely cats but never reported in birds. Twenty-six brown egg-laying chickens between ages 43 and 46 weeks had a history of feather loss, scaly, dry skin, weight loss, and decreased egg production. Microscopic findings in the skin included fragmentation of collagen bundles and interstitial, periadnexal, and perivascular dermal accumulation of wispy, mildly basophilic material that was also occasionally observed within the follicular epithelium. A moderate lymphoplasmacytic and heterophilic perivascular dermatitis was also observed. The wispy to granular material was diffusely Alcian blue positive and periodic acid-Schiff negative (consistent with mucin), suggesting a diagnosis of primary or secondary cutaneous mucinosis. The cause of this condition could not be determined.