Transcriptomic Profiles of Pectoralis major Muscles Affected by Spaghetti Meat and Woody Breast in Broiler Chickens.

Spaghetti meat (SM) and woody breast (WB) are breast muscle myopathies of broiler chickens, characterized by separation of myofibers and by fibrosis, respectively. This study sought to investigate the transcriptomic profiles of breast muscles affected by SM and WB. Targeted sampling was conducted on a flock to obtain 10 WB, 10 SM, and 10 Normal Pectoralis major muscle samples from 37-day-old male chickens. Total RNA was extracted, cDNA was used for pair-end sequencing, and differentially expressed genes (DEGs) were determined by a false discovery rate of <0.1 and a >1.5-fold change. Principal component and heatmap cluster analyses showed that the SM and WB samples clustered together. No DEGs were observed between SM and WB fillets, while a total of 4018 and 2323 DEGs were found when comparing SM and WB, respectively, against Normal samples. In both the SM and WB samples, Gene Ontology terms associated with extracellular environment and immune response were enriched. The KEGG analysis showed enrichment of cytokine-cytokine receptor interaction and extracellular matrix-receptor interaction pathways in both myopathies. Although SM and WB are macroscopically different, the similar transcriptomic profiles suggest that these conditions may share a common pathogenesis. This is the first study to compare the transcriptomes of SM and WB, and it showed that, while both myopathies had profiles different from the normal breast muscle, SM and WB were similar, with comparable enriched metabolic pathways and processes despite presenting markedly different macroscopic features.

Experimental infection of aquatic bird bornavirus 1 (ABBV-1) in Canada geese (Branta canadensis).

Aquatic bird bornavirus 1 (ABBV-1) has a high prevalence of infection in certain North American populations of Canada geese (Branta canadensis), suggesting a possible role of these birds as an ABBV-1 reservoir. The goal of this study was to evaluate the ability of Canada geese to become experimentally infected with ABBV-1, develop lesions, and transmit the virus to conspecifics. One-week-old Canada geese (n, 65) were inoculated with ABBV-1 through the intramuscular (IM) or cloacal (CL) routes, with the control group receiving carrier only. An additional 6 geese were added to each group to test horizontal transmission (sentinel birds). Geese were monitored daily, and selected birds were euthanized at 1, 8, and 15-weeks post infection (wpi) to assess virus replication in tissues and lesion development. At 15 wpi, over 70% of IM birds were infected, while the CL route yielded only 1 infected goose. Of the infected IM geese, 26% developed encephalitis and/or myelitis after 8 wpi. No clinical signs were observed, and no sentinel birds became infected in any group. Only 1 oropharyngeal swab (IM group) tested positive for ABBV-1 RNA, while the water from the enclosures was consistently negative for virus RNA. This study documents successful experimental infection of Canada geese with ABBV-1, with findings comparable to what is described in infection trials with other waterfowl species. However, minimal shedding and lack of environmental dispersal indicate that Canada geese have little potential to disseminate the virus among wild waterfowl, and that other species could be better suited to act as chronic ABBV-1 shedders in the wild.

Experimental pathogenesis of aquatic bird bornavirus 1 in Pekin ducks.

Aquatic bird bornavirus 1 (ABBV-1) is a neurotropic virus that causes persistent infection in the nervous system of wild waterfowl. This study evaluated whether Pekin ducks, the most common waterfowl raised worldwide, are susceptible to ABBV-1 infection and associated disease. Groups of Pekin ducks were inoculated with ABBV-1 through the intracranial (IC; n, 32), intramuscular (IM; n, 30), and choanal (CH; n, 30) routes. Controls (CO; n, 29) received carrier only. At 1, 12, and 21 weeks postinfection (wpi), 7-14 birds were euthanized to assess virus distribution and lesions. Infection rates in the IC and IM groups were over 70%, while only 4 ducks in the CH group became infected. Neurological signs were observed in 8 ducks only, while over 25% of IC and IM birds had encephalitis and/or myelitis. Seroconversion was highest in the IC and IM groups, and mucosal ABBV-1 RNA shedding was most frequent in the IC group (53%). None of the fertile eggs laid during the experiment tested positive for ABBV-1 RNA. This study shows that Pekin ducks are permissive to ABBV-1 infection and partly susceptible to associated disease. While mucosal shedding may be an important route of transmission, congenital infection appears unlikely.

Effects of broiler chilling methods on the occurrence of pale, soft, exudative (PSE) meat and comparison of detection methods for PSE meat using traditional and Nix colorimeters.

The aims of this study were to i) estimate the occurrence of pale, soft, and exudative (PSE) meat in modern commercial Ontario broiler flocks, ii) determine the effects of the chilling method (water vs. air) on PSE meat, and iii) investigate a new inexpensive colorimeter (10% of the price of traditional color meters), the Nix Color Sensor, as an objective color measurement of chicken meat. Between June 2019 to March 2020, a total of 17 different broiler flocks were processed. The color of 1,700 boneless skinless Pectoralis major muscles was randomly measured (100/flock), where 255 samples were also measured for pH, water-holding capacity (WHC), cooking loss, and penetration force. In addition, a traditional Minolta colorimeter was used to measure random 95 samples from a single water-chilled flock and subsequently compared the values obtained with the Nix Color Sensor. Strong correlations of L* values (rho = 0.75; P < 0.001), a* values (rho = 0.72; P < 0.001), and b* values (rho = 0.80; P < 0.001) were observed. When an L* value of 43 was used as the cut-off for the Nix, 12.5% of fillets were classified as PSE meat. Statistical differences (P < 0.05) were observed between the air and water-chill methods for L*, pH, and WHC. However, there were no significant differences observed between the 2 methods for cooking loss and penetration force values. The study indicated that PSE meat is still a challenge in Ontario broilers, and that the L*, pH, and WHC of breast meat (all indicate meat quality) are affected by the chilling method. In addition, the Nix was found to be an affordable, objective, and convenient sensor for measuring chicken meat color.

Textural and physical properties of breast fillets with myopathies (wooden breast, white striping, spaghetti meat) in Canadian fast-growing broiler chickens.

The combined effects of different severities of Wooden Breast (WB), White Striping (WS), and Spaghetti Meat (SM) were examined in 300 chicken breast fillets from 10 flocks. Severity (0 = absent, 1 = mild, noticeable upon close inspection, 2 = severe), noticeably altered from normal breast fillet (NB). Results showed that any combination of myopathies and severity resulted in significantly elevated compression force, pH and peak counts measured by the shear force test. With the exception of mild WB + mild WS, all combinations resulted in significantly higher drip loss, cooking loss and lightness value. Overall, the quality of fillets was affected the least by WS, while negatively affected the most by SM. There were limited effects on fillet quality from mild WB but major deleterious effects from severe WB.

Characterization of dorsal recumbency syndrome associated with woody breast in broiler flocks from Ontario, Canada.

A dorsal recumbency syndrome (DRS) has been recently described in market-age broiler chickens. Affected broilers fall onto their backs, and are unable to right themselves, and eventually die of cardiopulmonary insufficiency. These broilers are referred to as turtle chickens. A previous report and anecdotal evidence suggest that breast myopathies, such as woody breast (WB), may be associated with DRS due to impaired contractility of the pectoral muscles. In this study, we aimed to provide additional evidence to document DRS in broilers, and its possible association with breast myopathies. A total of 64 broilers (Ross 708), 33 DRS-affected and 31 controls, were culled between 42 and 48 d of age from 3 different commercial farms over 4 visits. All broilers underwent postmortem analysis; breast muscles were scored grossly and/or histologically to determine the presence and severity of myopathies, and sera were used to determine the level of aspartate aminotransferase (AST) and creatine kinase (CK). A gross diagnosis of WB was moderately associated with DRS broilers, and DRS broilers displayed a greater microscopic severity of lesions (P < 0.001) in the Pectoralis major, as typically observed with WB. Levels of AST and CK were greater (P < 0.001) in the sera of DRS-affected compared to control broilers, consistent with muscular damage. The frequency of cardiac changes, such as mild hydropericardium and right ventricular dilation, or severity of microscopic pulmonary lesions, such as edema, were not significantly different between the 2 groups. The odds of DRS increased with the histology score of the P. major (OR = 1.37, 95% CI 1.02-1.85). The data presented in this study support an association between DRS and muscular damage of the P. major, suggesting that WB may predispose broilers to DRS. DRS might be a cause of broiler death, and this syndrome could be responsible for significant financial loss to the farmers and to the whole poultry industry.

Experimental infection of aquatic bird bornavirus in Muscovy ducks.

Aquatic bird bornavirus (ABBV-1), an avian bornavirus, has been reported in wild waterfowl from North America and Europe that presented with neurological signs and inflammation of the central and peripheral nervous systems. The potential of ABBV-1to infect and cause lesions in commercial waterfowl species is unknown. The aim of this study was to determine the ability of ABBV-1 to infect and cause disease in day-old Muscovy ducks (n = 174), selected as a representative domestic waterfowl. Ducklings became infected with ABBV-1 through both intracranial and intramuscular, but not oral, infection routes. Upon intramuscular infection, the virus spread centripetally to the central nervous system (brain and spinal cord), while intracranial infection led to virus spread to the spinal cord, kidneys, proventriculus, and gonads (centrifugal spread). Infected birds developed both encephalitis and myelitis by 4 weeks post infection (wpi), which progressively subsided by 8 and 12 wpi. Despite development of microscopic lesions, clinical signs were not observed. Only five birds had choanal and/or cloacal swabs positive for ABBV-1, suggesting a low potential of Muscovy ducks to shed the virus. This is the first study to document the pathogenesis of ABBV-1 in poultry species, and confirms the ability of ABBV-1 to infect commercial waterfowl.

Prevalence of breast muscle myopathies (spaghetti meat, woody breast, white striping) and associated risk factors in broiler chickens from Ontario Canada.

Spaghetti meat (SM), woody breast (WB), and white striping (WS) are myopathies that affect the pectoral muscle of fast-growing broiler chickens. The prevalence and possible risk factors of these myopathies have been reported in other countries, but not yet in Canada. Thus, the objective of this study was to assess the prevalence and risk factors associated with these myopathies in a representative population of Canadian broilers. From May 2019 to March 2020, 250 random breast fillets from each of 37 flocks (total, 9,250) were obtained from two processing plants and assessed for the presence and severity of myopathies. Demographic data (e.g., sex and average live weight), environmental conditions during the grow-out period (e.g., temperature), and husbandry parameters (e.g., vaccination) were collected for each flock. Associations between these factors and the myopathies were tested using logistic regression analyses. The prevalence of SM, severe WB, and mild or moderate WS was 36.3% (95% CI: 35.3-37.3), 11.8% (95% CI: 11.2-12.5), and 96.0% (95% CI: 95.6-96.4), respectively. Most (85.1%) of the fillets showed multiple myopathies. Regression analyses showed that the odds of SM increased with live weight (OR = 1.30, 95% CI 1.01-1.69) and higher environmental temperature during the grow-out period (OR = 1.75, 95% CI 1.31-2.34). The odds of WB increased with live weight (OR = 1.23, 95% CI 1.03-1.47) and when flocks were not vaccinated against coccidia (OR = 1.86, 95% CI 1.51-2.29). This study documents for the first time a high prevalence of myopathies in Ontario broilers, and suggests that these lesions may have a significant economic impact on the Canadian poultry industry. Our results indicate that environmental conditions and husbandry are associated with the development of breast myopathies, in agreement with the current literature. Future studies are needed to determine how risk factors can promote the occurrence of these conditions, in order to implement possible mitigating strategies.

Characteristics of broiler chicken breast myopathies (spaghetti meat, woody breast, white striping) in Ontario, Canada.

Spaghetti meat (SM), woody breast (WB), and white striping (WS) are myopathies affecting breast muscle of broiler chickens, and are characterized by a loss of myofibers and an increase in fibrous tissue. The conditions develop in intensive broiler chicken production systems, and cause poor meat process-ability and negative customer perception leading to monetary losses. The objectives of the present study were to describe the physical and histological characteristics of breast myopathies from commercial broiler chicken flocks in Ontario, Canada, and to assess the associations between the severity of myopathies with the physical and histological characteristics of the affected breast muscle fillets. Chicken breast fillets (n = 179) were collected over 3 visits from a processing plant and scored macroscopically to assess the severity of myopathies, following an established scoring scheme. For each fillet, the surface area, length, width, thickness, weight, and hardness (compression force) were measured. A subset of 60 fillets was evaluated microscopically. Multinomial logistic regression models were built to evaluate associations between physical parameters and macroscopic scores. The odds of SM co-occurring with severe WB (SM1WB2) were significantly associated with increased fillet thickness (OR = 1.59, 95% CI 1.31-1.94) and weight (OR = 1.06, 95% CI 1.03-1.09). Histologically, myopathies had overlapping lesions consisting of polyphasic myodegeneration, perivascular inflammatory cuffing and accumulation of fibrous tissue and fat. The pairwise correlation between macroscopic and microscopic scores was moderate (rho 0.45, P < 0.001). This is the first study to characterize breast myopathies in Canadian broiler flocks. Results show that the morphologic and microscopic changes of fillets from this cohort are similar to data from other countries, and provide database to benchmark these parameters in future studies. Our standardized categorization can be applied to broiler breast fillets in other regions of the world.