Broiler production performance declined, with a 50-60% reduction in farm output characterized by low body weight gain, decreased feed intake and suboptimal feed conversion. But there was no increase in mortality and average mortality was 3.19%. In most of the farms, 15-20% of the droppings contained orange mucoid with undigested feed particles. Feed passage (undigested maize particles in birds’ feces) was observed throughout the house (Fig 2) and a decline in body weight gain was observed and was lower than the breed standards. During the examination of GIT, hepatomegaly, focal hepatic necrosis in the liver with a pale color and hydropericardium were observed (Fig 5A, B and C). The presence of gizzard erosion (GE) was the most common observation and 52.78% of birds found GE in examined for GIT assessments. Affected gizzards had reduced musculature which appeared flaccid and moderate to severe erosions of the keratinoid layer as well as inflammatory changes and ulceration underneath the gizzard mucosa (Fig 4A, B and C). During intestinal health examination, poorly digested maize particles were observed in the content of the distal ileum and cloaca part (Fig 3D). Proventriculus was found to be normal. In most of the birds, mild to moderate
Eimeria acervulina,
Eimeria maxima and
Eimeria tenella were observed (Fig 3A, B and C) and Total means lesion scoring (TMLS) scores were 0.78, 1.67 and 0.67 in Sirajganj, Tangail and Pabna area, respectively (Fig 6). The dysbacteriosis lesion scores were found to be below 1 in the Sirajganj and Pabna, areas and 1.11 in the Tangail area (Fig 6).
The feed provided to all these flocks was formulated with plant-origin ingredients. Raw materials from animal protein sources were not used in the feed. In the feed samples submitted for mycotoxin analysis, all mycotoxins (Aflatoxin B1, Ochratoxin, Citrinin, Zearalenone (ZON), Cyclopiazonic acid (CPA), Fumonisin B1, B2 and B3) were below the limit of quantification (Table 1).
All gizzard and liver impression smear samples submitted for the detection of FAdV by PCR were found positive for FAdV (Table 2). All positive samples were further processed for sequencing of the Hexone gene of FAdV. Phylogenetic analysis of the gene fragment indicated a resemblance to fowl adenovirus serotype 11 in two samples and serotype 8b in another two samples (Table 2 and Fig 7, 8, 9 and 10).
In recent times, gizzard erosion (GE) and ulceration syndrome (GEU) has been very common in poultry at mild to moderate levels
(Contreras, 2016). It usually causes reduced feed intake, growth, poor absorption of nutrients and persistent diarrhea in birds, which leads to economic losses
(Wang et al., 2021). On the other hand, feed passage syndrome (FPS) has emerged as a common problem in broilers. This passage of undigested feed into feces has had a significant impact on weight gain, FCR and flock uniformity, ultimately leading to a severe loss of productivity
(Butcher et al., 2002). A similar observation was found in the present study as well. Most of the farm’s birds’ body weight gain decline, low feed intake and high feed conversion ratio (FCR) were observed and were lower than the breed standards.
Multiple factors play a role in the development of gizzard erosion, including congenital factors, starvation, malnutrition, feed material, toxicants (copper sulphate, biogenic amines, gizzerosine and mycotoxin, such as T-2 toxin, MAS, DAS, DON) and viral/bacterial infection
(Haque et al., 2023).
Gizzard and koilin lesions have been observed in chick embryos and newly hatched broiler chicks, suggesting that gizzard erosion and ulceration (GEU) may be congenital and influenced by factors before hatch
(Gjevre et al., 2013). However, no congenital history was found in the present study and early chicks’ postmortem examination did not show gizzard erosion lesions. Newly hatched chicks deprived of feed and water experienced an increase in ulcerated gizzards, from 3 to 68% on day 4 post-hatch. Restriction or deprivation of food and water may be associated with increased frequency and severity of lesions
(Haque et al., 2024). However, no starvation history was found on farms in these areas, so congenital starvation as a causative factor for gizzard erosion was ruled out.
Malnutrition status, like deficiency of vitamin B6, vitamin B12, vitamin E, methionine and decreased sulfur-containing amino acids, is associated with gizzard ulceration
(Gjevre et al., 2013). In the current study, we analyzed all feed samples in the feed nutrition lab and proximate analysis showed that the nutrition values adhered to the breed diet standards, but we did not analyze the vitamins and minerals.
Feed-related factors of gizzard erosion such as copper sulfate, biogenic amines, gizzerosine and mycotoxins are the major ones
(Masumura et al., 1981; Gjevre et al., 2013). High levels of copper sulfate can lead to ulceration of the gizzard lining
(Luo et al., 2005), while biogenic amines (histamine), found in poorly processed animal protein sources, catalyze gastric acid secretion
(Barnes et al., 2001). Besides this, poor-grade fish meals produce gizzerosine [2-amino-9-(4-imidazoyl)-7-azanonanoic acid], which is an even more effective stimulator of gastric acid secretion in poultry and causes gizzard erosion in chickens
(Masumura et al., 1981). As a result, biogenic amines and gizzerosine cause proventricular enlargement, gizzard erosion, sloughing of intestinal epithelia, poor weight gain and feed conversion, impaired immune response and feed passage syndrome
(Butcher et al., 2002). Affected birds are poorly pigmented and have low body weights and feed conversions. The study found that none of the examined farms received any animal protein sources or copper sulfate in their feed, eliminating the possibility of these factors causing gizzard erosion and feed passage syndrome.
Among mycotoxins, Trichothecenes are a group of Fusarium mycotoxins, including T-2 Toxin, Monoacetoxyscirpenol (MAS), Diacetoxyscirpenol (DAS), Deoxynivalenol (DON) and HT-2 Toxin, which can cause gizzard erosion
(Gjevre et al., 2013). Fumonisins and cyclopiazonic acid (CPA) are potent in causing GE
(Gjevre et al., 2013). Feeds containing mycotoxins, like aflatoxin and ochratoxin, cause syndrome in feed passage, leading to intestinal wall erosion, liver damage, reduced bile and digestive enzyme production and poor digestion
(Butcher et al., 2002). In the feed samples collected from the study regions, Trichothecene was not assessed in any of the feed samples and other mycotoxins known to cause FPS (aflatoxin, ochratoxin) and GE (CPA and fumonisins) were assessed in these feed samples and were either not present or were below the limit of quantification.
Researchers have found that
Bacillus cereus (B.
cereus) isolates cause gizzard erosion and ulceration syndrome (GEU) in birds, potentially leading to vomiting, diarrhea, or ulceration
(Ono et al., 2003). Clostridium perfringens was discovered to be an opportunistic bacterium in commercial chickens with gizzard ulcerations and the severity of the lesions was observed to considerably increase caecal numbers
(Tsilia et al., 2016). In the present study,
Bacillus cereus (
B.
cereus) and
Clostridium perfringens samples were not collected from the study region and were isolated in the microbiological lab.
Coccidiosis, particularly in younger broilers, can damage the intestine lining, allowing undigested nutrients to pass through feces
(Ram et al., 2020). E.
acervulina and E.
maxima are commonly associated with feed passage
(Butcher et al., 2002). Bacterial enteritis often occurs after viral or coccidial infections, with
E.
acervulina and E.
maxima, causing damage to the gut lining, reducing intestinal passage and allowing overgrowth of
C.
perfringens, leading to necrotizing enteritis
(Butcher et al., 2002). In the present study,
E.
acervulina and
E.
maxima lesion scored 0.67, 2.67,0 and 0,1, 0.44 in Sirajganj, Tangail and Pabna areas respectively. TMLS scores are 0.78, 1.67 and 0.67 in Sirajganj, Tangail and Pabna. In the lesion scoring of the GIT tract, no lesion related to necrotic enteritis (the causal agent of
Clostridium perfringens) and dysbacteriosis score below 1 in the Sirajganj and Pabna areas and 1.11 slightly higher in the Tangail area. Observation is that TMLS and dysbacteriosis score was not so high except Tangail area for TMLS score and dysbacteriosis. So, it could be interpreted that coccidiosis and dysbacteriosis can also be the contributing factors for the feed passage syndrome in affected flocks. Also, the effect of FPS increases when FAdV is infected in flocks.
FAdV, induced IBH, is another infectious factor that causes gizzard erosion
(Butcher et al., 2002). In Bangladesh, gizzard erosion (11% of suspected IBH cases) and hemorrhage of muscle are two of the most common symptoms
(Saleque, 2020). However, new studies show that gizzard erosion is more common in IBH cases. Most cases of GE have revealed the presence of FAdV in the affected birds. Certain pathogenic strains of FAdV significantly impact the health and performance of healthy chickens, despite adenoviruses being detected in healthy chickens
(Yates et al., 1976). Pathogenic strains of FAdV significantly affect birds’ health and performance. Factors such as chicken breed, immune system status and concurrent infections with other immunosuppressive agents influence the mortality and severity in adenoviral infections
(Wani et al., 2014). The status of the birds’ immune systems also plays a key role in determining the severity of FAdV infection. FAdV infection manifests severely in immunocompromised birds
(Fadly et al., 1976). Pathogenicity of adenoviruses may vary among strains belonging to the same serotype
(Absalón et al., 2017). FAdV manifestations like gizzard erosion may not show clinical symptoms or significantly increase mortality but still impact body weight gain and feed conversion
(Mirzazadeh et al., 2021).
Most GE cases worldwide have identified FAdV serotype 1
(Das and Shelke, 2024;
Okuda et al., 2004; Ono et al., 2003; Domanska-Blicharz et al., 2011). In Japan and Iran, birds with GE isolated FAdV serotypes 8 and 11
(Okuda et al., 2004). In India, GE cases in commercial layer chicken identified FAdV serotypes 2, 3, 4, 8 and 11
(Lim et al., 2012; Chitradevi et al., 2020) and commercial broilers identified fowl adenovirus-induced gizzard erosion serotypes 8a and 11in southern India
(Shankar et al., 2022; Das and Shelke, 2024). Bangladesh detected three serotypes of IBH, specifically 8b (70%), 11 (10%) and 5 (10%), but did not report any gizzard erosion lesions
(Islam et al., 2023). Phylogenetic analysis revealed that the Bangladeshi FAdVs have a close identity with viruses from Asia, Europe and South and North America
(Islam et al., 2023). This study found that all the tissue impression samples were positive for FAdV. This, in line with other researchers’ findings, suggests that FAdV plays a role in causing GE in broiler chickens.
The present study detected FAdV serotypes 8b and 11 in the tissue impression samples, which contrasts with the majority of studies that found FAdV serotype 1. Some studies have demonstrated that FAdV-induced GE has an economic impact on the affected flock, leading to impaired body weight gain and increased mortality, while others have revealed poor performance and lower mortality
(Mirzazadeh et al., 2021; Das and Shelke, 2024). In the present study, though there was no significant increase in mortality, all the affected flocks had lower body weight gain than the breed standards. Feed passage syndrome (FPS) is also caused by multiple etiological factors and FAdV is one of them
(Butcher et al., 2002). Any condition or factors affecting GIT will impair the digestion process leading to the excretion of poorly digested feed particles in the feces. FAdV has been identified from GIT of broilers having enteric disease conditions and feed passage problems
(Das and Shelke, 2024). A similar observation was found in the present study as well. Feed passage was observed in all the visited farms with varying severity. There are many common causes of gizzard erosion and FPS and adenovirus is one of them. Gizzard erosion caused by adenovirus causes problems in the GIT tract in the form of feed passage syndrome and other factors play a role. This results in low body weight gain of birds, high FCR, poor performance and economic losses to the farms.
