Abomasal Ulcers and Abomasitis

Abomasal ulcers and abomasitis are common, economically significant disorders of the bovine abomasum, the true glandular stomach of ruminants. Abomasitis refers to inflammation of the abomasal mucosa, often with varying degrees of erosion, ulceration, and hemorrhage. Abomasal ulcers are localized defects in the mucosal lining that can be classified into four types based on depth and clinical severity: Type I (non-perforating, superficial erosions), Type II (non-perforating, deep ulcers with hemorrhage), Type III (perforating with localized peritonitis), and Type IV (perforating with diffuse peritonitis). These conditions occur across all production stages but are particularly prevalent in high-producing dairy cows during the periparturient period and in young calves, especially those fed high-concentrate diets or subjected to stress. The economic impact stems from reduced milk production, decreased weight gain, treatment costs, increased culling, and mortality, particularly in severe cases. Abomasal ulcers and abomasitis are often part of a complex of digestive disorders linked to ruminal acidosis, stress, and management practices.

The etiology of abomasal ulcers and abomasitis is multifactorial. Primary causes include dietary factors such as high concentrate-to-forage ratios, finely ground grains, and low fiber content, which lead to increased production of volatile fatty acids (VFAs) and a drop in abomasal pH. Excessive fermentation in the rumen can produce histamine and other vasoactive amines that may contribute to mucosal damage. Stress, including parturition, transport, overcrowding, and social regrouping, is a major trigger, often associated with elevated cortisol levels that reduce mucosal protective mechanisms. Bacterial involvement is significant, particularly with Clostridium perfringens type A, which produces alpha toxin, and type C, which produces beta toxin, both implicated in abomasitis and ulceration, especially in calves. Viral agents such as bovine viral diarrhea virus (BVDV) and bovine coronavirus can cause mucosal damage and immunosuppression, predisposing to secondary bacterial invasion. Fungal infections, particularly with Aspergillus species, can occur in immunocompromised animals. Parasitic infections, such as ostertagiasis, can cause abomasal damage, though less commonly associated with ulcers. Nutritional deficiencies, including copper, selenium, and vitamin E, may impair mucosal integrity. Additionally, the use of non-steroidal anti-inflammatory drugs (NSAIDs) can cause ulceration due to inhibition of prostaglandin synthesis, which is cytoprotective.

Abomasal ulcers and abomasitis are reported worldwide, with a higher incidence in intensively managed dairy herds and feedlot cattle. In dairy cattle, the prevalence of abomasal ulcers at slaughter ranges from 5% to 20%, with higher rates in high-producing cows, particularly during the first few weeks after calving. The condition is more common in mature cows (second lactation and greater) than in heifers. In calves, abomasitis is often seen in the first few weeks of life, especially in those fed large volumes of milk or milk replacer, or those subjected to stress. Seasonal patterns may exist, with increased cases in winter when cows are housed indoors and fed high-concentrate diets. Morbidity can be high in affected herds, with clinical cases occurring in 1-5% of cows annually, but subclinical ulcers are much more common. Mortality is significant in cases of perforation, with case fatality rates exceeding 50% for Type IV ulcers. Economic losses include reduced milk yield (estimated at 10-20% in affected cows), increased veterinary costs, premature culling, and death loss.

The pathophysiology of abomasal ulcers and abomasitis involves a complex interplay of mucosal injury, impaired protective mechanisms, and systemic consequences. Under normal conditions, the abomasal mucosa is protected by a mucus-bicarbonate barrier, rapid cell turnover, and adequate mucosal blood flow. High-concentrate diets lead to increased production of VFAs, particularly propionic and butyric acids, which can diffuse into mucosal cells, causing intracellular acidification and cell damage. A drop in abomasal pH below 2.0 can overwhelm the buffering capacity, leading to direct mucosal injury. Histamine, released from mast cells and dietary sources, can cause vasoconstriction and increased vascular permeability, exacerbating ischemia and edema. Stress-induced cortisol elevation reduces mucosal blood flow and mucus production, impairing repair mechanisms. Bacterial toxins, such as Clostridium perfringens alpha and beta toxins, cause direct cellular damage and necrosis. In calves, abomasitis often results from excessive milk feeding, leading to abomasal distension, delayed emptying, and fermentation, which produces lactic acid and volatile fatty acids, further damaging the mucosa. Ulceration can lead to hemorrhage, which may be acute and severe, resulting in anemia and shock. Perforation allows abomasal contents to leak into the peritoneal cavity, causing localized or diffuse peritonitis, which can be rapidly fatal due to endotoxemia and septic shock.

Predisposing factors for abomasal ulcers and abomasitis include intrinsic and extrinsic elements. Intrinsic factors include high milk production, which increases metabolic demands and stress on the digestive system; parity, with older cows more susceptible; genetics, as certain bloodlines may have a higher incidence; and transition period stress, which involves hormonal changes, negative energy balance, and immunosuppression. Extrinsic factors are primarily management-related: ration formulation errors such as excessive concentrate, insufficient effective fiber, and poor feed particle size; abrupt diet changes; inadequate bunk space leading to slug feeding; poor feed hygiene with mycotoxins; overcrowding and poor ventilation; dirty bedding and unhygienic conditions; and stressful events like calving, transport, and regrouping. Additionally, the use of NSAIDs for other conditions can predispose to ulceration. In calves, factors include overfeeding, feeding inconsistent milk temperatures, and poor colostrum management leading to failure of passive transfer and increased susceptibility to infections.

Clinical signs of abomasal ulcers and abomasitis vary depending on the severity and type of lesion. Type I ulcers are often subclinical and may only be detected at slaughter. Type II ulcers present with signs of blood loss, including pale mucous membranes, tachycardia, tachypnea, weakness, and melena (dark, tarry feces). In severe hemorrhage, cows may show signs of shock, such as cold extremities, depression, and collapse. Type III and IV ulcers cause peritonitis, with signs including fever, anorexia, decreased rumen motility, abdominal pain (grunting, kicking at the abdomen), and a 'ping' on percussion over the abomasum due to gas accumulation. In calves with abomasitis, signs include abdominal distension, pain, diarrhea, dehydration, and sometimes sudden death. On herd examination, affected cows may be separated from the group, show reduced feed intake, and have a drop in milk production. Rumen motility is often decreased or absent. Fecal examination may reveal dark, tarry stools due to digested blood. In cases of perforation, there may be a localized or diffuse peritonitis, with a painful response on deep palpation of the abdomen.

Differential diagnoses for abomasal ulcers and abomasitis include: 1) Traumatic reticuloperitonitis (hardware disease), which presents with similar signs of abdominal pain and peritonitis, but is differentiated by the presence of a metallic foreign body in the reticulum, detectable by radiography or ultrasonography, and a characteristic 'ping' over the reticulum. 2) Abomasal displacement (left or right), which can cause a 'ping' but is usually not associated with hemorrhage or peritonitis; diagnosis is confirmed by auscultation and percussion over the left or right flank. 3) Intestinal obstruction (e.g., intussusception, volvulus), which presents with acute abdominal pain, distension, and lack of feces; differentiation is via rectal palpation and ultrasonography. 4) Peritonitis from other causes, such as uterine rupture or liver abscess, which may have a history of recent calving or other abdominal surgery. 5) Salmonellosis, which causes diarrhea and fever, but is differentiated by fecal culture and the presence of inflammatory cells in feces. 6) Bovine viral diarrhea (BVD), which can cause mucosal lesions and diarrhea, but is differentiated by serology and virus isolation. 7) Clostridial enterotoxemia, especially in calves, which presents with sudden death and abomasitis; diagnosis is via toxin detection and necropsy findings. 8) Heavy metal toxicity (e.g., lead), which can cause gastrointestinal signs and neurological signs, differentiated by blood lead levels. 9) Uremia due to kidney failure, which can cause oral ulcers and gastrointestinal bleeding, differentiated by blood urea nitrogen and creatinine levels. 10) Rumen acidosis, which can cause similar dietary history and systemic signs, but is differentiated by rumen fluid pH and absence of abomasal lesions on necropsy.

The diagnostic approach to abomasal ulcers and abomasitis involves a stepwise process: 1) Obtain a thorough herd history, including diet, recent management changes, calving history, and any previous cases. 2) Perform a complete physical examination, including assessment of vital parameters, rumen motility, abdominal auscultation and percussion for 'pings', and rectal palpation. 3) Evaluate fecal color and consistency; melena suggests upper gastrointestinal bleeding. 4) Perform a rumenocentesis or rumen fluid analysis to assess rumen pH and VFA profile; a pH below 5.5 indicates acidosis. 5) Collect blood samples for CBC, serum biochemistry, and blood gas analysis; look for anemia, leukocytosis or leukopenia, elevated fibrinogen, and electrolyte imbalances. 6) If peritonitis is suspected, perform abdominocentesis and analyze peritoneal fluid for protein, cell count, and cytology. 7) Use ultrasonography to evaluate the abomasum, liver, and peritoneal cavity; look for abomasal wall thickening, free fluid, and abscesses. 8) In cases of suspected perforation, radiography may be helpful to detect free gas in the abdomen. 9) In calves, consider specific tests for Clostridium perfringens toxins in feces or intestinal contents. 10) If the animal dies or is euthanized, perform a thorough necropsy to confirm the diagnosis and identify the type of ulcer.

Laboratory findings in abomasal ulcers and abomasitis include: Blood BHB (beta-hydroxybutyrate) levels may be elevated (>1.2 mmol/L) in cows with concurrent ketosis, but this is not specific. Ionized calcium may be low (<1.0 mmol/L) due to decreased feed intake and acidosis. Magnesium and phosphorus may be altered. NEFA (non-esterified fatty acids) are often elevated in periparturient cows due to negative energy balance. Rumen fluid analysis typically shows a pH below 5.5, reduced protozoal motility, and a prolonged methylene blue reduction time (>6 minutes). Gram stain may show a shift towards Gram-positive bacteria. CBC may reveal anemia (decreased PCV, hemoglobin) in cases of hemorrhage, leukocytosis with a left shift in peritonitis, or leukopenia in severe endotoxemia. Fibrinogen levels are often elevated (>700 mg/dL) in inflammatory conditions. In cows with concurrent mastitis, the California Mastitis Test (CMT) may be positive, and somatic cell count (SCC) may be elevated (>200,000 cells/mL). However, these findings are not specific to abomasal ulcers.

Ultrasonography is a valuable tool in diagnosing abomasal ulcers and abomasitis. Findings may include thickening of the abomasal wall (>5 mm), which can be seen as a hypoechoic or heterogeneous layer. In cases of perforation, free fluid with echogenic particles may be present in the peritoneal cavity, and there may be evidence of localized abscesses. The abomasum may be displaced, and its position can be assessed. Ultrasonography can also evaluate the liver for lipidosis, which is often concurrent. Radiography is less commonly used in adult cattle due to size, but in calves, it can detect free gas in the abdomen or a metallic foreign body. Endoscopy or laparoscopy may be used in research settings or for direct visualization of the abomasal mucosa, but is not routinely performed in practice.

Cytological examination of peritoneal fluid in cases of peritonitis typically shows increased protein (>3 g/dL), elevated nucleated cell count (>10,000 cells/µL), and a predominance of neutrophils, often with degenerative changes. Histopathology of abomasal tissue obtained at necropsy or biopsy reveals mucosal erosion, ulceration, and necrosis, with infiltration of neutrophils and mononuclear cells. In cases of clostridial infection, there may be evidence of bacterial colonization and toxin-induced damage. Hepatic histopathology may show lipid vacuolation in cows with fatty liver. In calves, histopathology of the abomasum may show necrotizing abomasitis with thrombosis and hemorrhage.

Treatment of abomasal ulcers and abomasitis depends on the severity and type. For mild cases (Type I), dietary management is key: reduce concentrate, increase forage, and provide a high-fiber diet. For Type II ulcers with hemorrhage, emergency stabilization is required: administer IV fluids (e.g., isotonic crystalloids) to correct shock and anemia, and consider blood transfusion if PCV is very low (<15%). Use systemic hemostatic agents such as vitamin K1 (1 mg/kg SC) and aminocaproic acid (5-10 g IV). For Type III and IV ulcers with peritonitis, aggressive therapy is needed: broad-spectrum antibiotics (e.g., ceftiofur 2.2 mg/kg IM q24h, or oxytetracycline 10 mg/kg IV q24h) and anti-inflammatory drugs (e.g., flunixin meglumine 1.1-2.2 mg/kg IV q24h). Surgical intervention may be necessary for perforated ulcers, involving exploratory laparotomy and closure of the perforation, but prognosis is poor. In calves with abomasitis, treatment includes fluid therapy, antibiotics, and supportive care. Nutritional support with oral electrolytes and gradual reintroduction of milk is essential. In all cases, correct any underlying metabolic disturbances, such as ketosis, with propylene glycol (250-300 mL PO q24h) or dextrose IV.

The prognosis for abomasal ulcers and abomasitis varies. Type I ulcers have a good prognosis with dietary correction. Type II ulcers have a guarded prognosis, as severe hemorrhage can be fatal; however, with prompt treatment, many cows recover. Type III ulcers have a fair to guarded prognosis, as localized peritonitis may resolve with medical therapy. Type IV ulcers have a poor prognosis, with high mortality despite surgical intervention. In calves, abomasitis can be fatal if not treated early, but with aggressive therapy, recovery is possible. Negative prognostic indicators include severe anemia (PCV <15%), hypothermia, recumbency, and evidence of diffuse peritonitis. Cows that recover may have reduced milk production in the current lactation but can return to normal in subsequent lactations.

Follow-up care for affected cows includes monitoring for recurrence of clinical signs, serial blood work (PCV, fibrinogen, BHB) to assess recovery, and gradual reintroduction of a balanced diet. Herd-level follow-up involves reviewing the ration formulation to ensure adequate fiber and particle size, minimizing stress, and improving hygiene. For cows with concurrent ketosis, monitor BHB levels weekly until normalized. For calves, monitor weight gain and fecal consistency. Implement a transition cow management program to reduce the incidence of abomasal disorders.

Clinical pearls: 1) A 'ping' over the right flank in the abomasal region may indicate abomasal displacement or ulcer with gas accumulation; differentiate by auscultation and percussion. 2) Melena is a classic sign of abomasal ulcer hemorrhage; check the tail and perineum for dark, tarry feces. 3) In cases of peritonitis, abdominocentesis is crucial; a sample with foul odor and high protein indicates a poor prognosis. 4) Always check for concurrent diseases like ketosis and fatty liver, as they complicate treatment. Pitfalls: 1) Do not use NSAIDs in cows with suspected ulcers, as they can worsen the condition. 2) Avoid oral administration of medications in cows with severe abomasal disease, as it may exacerbate the condition. 3) Do not delay surgical intervention in cases of perforation, as the prognosis deteriorates rapidly. 4) In calves, do not overfeed milk replacer, as it can cause abomasitis; follow feeding guidelines strictly.

Current drug protocols for abomasal ulcers and abomasitis include: 1) Fluid therapy: Isotonic crystalloids (e.g., lactated Ringer's solution) at 40-60 mL/kg IV over 1-2 hours for shock, then maintenance at 80-120 mL/kg/day. Hypertonic saline (7.2% NaCl) at 4-5 mL/kg IV over 10-15 minutes for rapid volume expansion, followed by oral water. 2) Calcium supplementation: 23% calcium borogluconate (500 mL IV slowly) for hypocalcemia, if present. 3) Propylene glycol: 250-300 mL PO q24h for 3-5 days for ketosis. 4) Antibiotics: Ceftiofur (2.2 mg/kg IM q24h for 3-5 days), Oxytetracycline (10 mg/kg IV q24h), Ampicillin (10-20 mg/kg IM q12h), or Penicillin G procaine (20,000 IU/kg IM q24h). 5) Anti-inflammatory: Flunixin meglumine (1.1-2.2 mg/kg IV q24h for 1-3 days) or Meloxicam (0.5 mg/kg SC once). 6) Gastroprotectants: Sucralfate (20-30 mg/kg PO q8h) or Omeprazole (1 mg/kg PO q24h) may be used, though evidence is limited. 7) Vitamin K1 (1 mg/kg SC) for hemorrhage. 8) In calves, oral electrolytes and antibiotics (e.g., amoxicillin 10 mg/kg PO q12h) are used. Withdrawal times must be observed for milk and meat.

Evidence-based literature on abomasal ulcers and abomasitis is limited but includes key studies: 1) A study by Constable et al. (2009) in 'Veterinary Medicine' highlighted the role of ruminal acidosis in the pathogenesis of abomasal ulcers. 2) Research by Divers and Peek (2008) in 'Rebhun's Diseases of Dairy Cattle' provided comprehensive clinical descriptions and treatment recommendations. 3) A field trial by Staufenbiel et al. (2010) demonstrated that feeding a total mixed ration with adequate particle size reduced the incidence of abomasal ulcers in dairy cows. 4) Studies on Clostridium perfringens in calves have shown that vaccination of dams can reduce the incidence of abomasitis in calves. 5) The AABP (American Association of Bovine Practitioners) has published guidelines on the management of digestive disorders in cattle, emphasizing prevention through nutrition and stress reduction. 6) A meta-analysis by LeBlanc et al. (2005) on transition cow diseases found that subclinical ketosis is a risk factor for abomasal displacement, which is often associated with ulcers. Overall, the evidence supports a multifactorial approach to prevention and treatment.