Metabolic Diseases in Food Animals - 2

Metabolic Diseases in Food Animals

Pregnancy Toxemia

  • Definition: A disease primarily affecting small ruminants and beef cattle, also referred to as:

    • Sleepy sickness

    • Twin lamb disease

    • Lambing sickness

  • Pathophysiology:

    • Associated with ketosis during late pregnancy.

    • Increased energy demand arises from one or more fetuses.

    • The condition is more prevalent in animals carrying multiple fetuses.

    • Decreased ruminal fill is observed.

    • Often occurs in animals that are overconditioned in early pregnancy (ideal body condition is 2.5-3 / 5).

Signalment and History

  • Affected Species: Small ruminants (e.g., sheep and goats).

  • Body Condition: Can be thin or obese, with the issue often presenting in the last month of gestation.

    • Gestational Factors:

    • Single large fetus

    • Twins

    • Triplets

  • Fetal Growth: 70-80% of fetal growth occurs within the last 2 months of pregnancy.

  • Physiological Impact: Limited abdominal space due to increased fetal size leads to decreased ruminal fill.

Risk Factors

  • Diet:

    • Sudden sudden changes in dietary intake can predispose animals to the disease.

    • Environmental factors such as winter conditions leading to limited pasture access and poor-quality feed can contribute.

    • Sudden stresses such as storms, snow, predator attacks, or hauling can exacerbate the condition.

  • Example: A local farmer in China hauling sheep on a motorcycle, potentially causing unexpected stress on the animals.

Clinical Signs

  • Symptoms Includes:

    • Anorexia (lack of appetite)

    • Depressed mentation (reduced awareness)

    • Animals may separate from the herd

    • Possible grinding of teeth

    • Tremors observed during clinical examination

    • Star-gazing (abnormal posture of looking upwards)

    • Ataxia (lack of voluntary coordination of muscle movements)

    • Recumbency (inability to stand)

    • Blindness in some cases.

  • Note: Recumbency is often seen in the early stages of the disease.

Diagnosis

  • Key Diagnostic Indicators:

    • Ketonuria (presence of ketone bodies in urine)

    • Ketonemia (presence of ketones in the blood)

    • BHB (Beta-Hydroxybutyrate) levels greater than 0.8 - 1 mmol/L.

    • Signs of metabolic acidosis

    • Hypocalcemia (low calcium levels) in late gestation

    • Hypokalemia (low potassium levels) particularly in anorexic animals

    • Azotemia (elevated levels of nitrogen in the blood)

    • Increased liver enzyme levels indicate liver involvement.

    • Variability is noted among sheep.

Treatment

  • Goals of Treatment: Restore energy balance in affected animals.

  • Methods Include:

    • Providing energy-dense feed to affected animals.

    • Use of propylene glycol as a source of carbohydrates.

    • Transfaunation (introducing rumen contents from a healthy donor animal).

    • Intravenous administration of glucose and insulin.

    • Removal of fetuses which may be causing ongoing energy drain through:

    • Induction of labor.

    • C-section (cesarean section).

  • Conservative Treatment Options:

    • Oral propylene glycol (150-200 mL every 12 hours or 60 mL every 12 hours for 3-6 days).

    • +/- Oral CMPK (Calcium, Magnesium, Phosphorus, Potassium) paste.

  • Aggressive Treatment Options:

    • IV administration of dextrose (250-500 mL of 10-20% solutions).

    • Continuous IV dextrose CRI (constant rate infusion) of 2.5-5% dextrose in isotonic fluid.

    • +/- IV or oral calcium and potassium.

Prevention

  • Preventive Strategies:

    • Identify 'at-risk' animals and separate them for specialized feeding.

    • Use transabdominal ultrasound to count the number of fetuses.

    • Ensure dietary management with body condition scoring targeting 2.5-3 / 5 at parturition.

    • Implement a careful diet during late gestation.

    • Regular monitoring for ketones during the last month of gestation.

Negative Energy Balance

  • Definition and Concern:

    • A critical concern in high-producing dairy cows where energy intake is insufficient to meet demands, especially during transition periods.

Fatty Liver Disease (Hepatic Lipidosis)

  • Pathophysiology:

    • Characterized by a significant build-up of lipids in the liver, constituting 12-25% of the liver's wet weight.

    • This leads to:

    • Inflammation.

    • Scarring and hardening of liver tissue.

    • Increased susceptibility to additional diseases.

  • Visual Characteristics:

    • Presents with yellowish coloration and a spongy appearance with rounded edges during surgery (surgical examination).

Relationship Between Fatty Liver and Ketosis

  • Connection: The two conditions are interrelated as they both depict the cow’s metabolic response to negative energy balance.

  • Primary Concerns:

    • Fatty liver primarily involves compromised liver function due to fat accumulation.

    • Ketosis involves excessive production of ketones leading to metabolic acidosis.

  • Management Strategies:

    • Both conditions necessitate optimizing nutrition during transition periods, managing body condition scores, and reducing environmental and physiological stresses.

    • Supplementation with propylene glycol or other glucose precursors is helpful in managing ketosis.

    • Preventing fatty liver involves careful energy management prior to calving.

Diagnosis of Fatty Liver

  • Diagnostic Challenges: Often assessed indirectly through metabolic indicators and liver function markers.

  • Key Assessments Include:

    • Indirect indicators show the severity and duration of negative energy balance (NEB).

    • Elevated liver enzymes (e.g., AST and SDH) indicate possible liver dysfunction or failure.

    • Hypoglycemia levels below 75 mg/dL.

    • Increased levels of Non-Esterified Fatty Acids (NEFA), indicating less uptake.

    • Decreased serum triglycerides (VLDL) and low blood urea nitrogen (BUN) levels.

    • Hyperammonemia and elevated bile acids and bilirubin.

Liver Biopsy for Diagnosis

  • Process: A minimally invasive procedure that is the most reliable method for assessing fatty liver's severity in dairy cattle. It involves measuring:

    • Total lipid or triglyceride content of liver tissue.

    • Evaluation of liver TAG (triglyceride) levels.

  • Techniques Used:

    • Liver ultrasound to estimate fat content.

    • Necropsy as a diagnostic tool if necessary.

Miscellaneous Diagnostic Tools (Ultrasound Imaging)

  • Liver Imaging Assessment:

    • Transabdominal ultrasound used for guiding biopsies.

    • Best performed on the right side at the 6th-12th intercostal spaces (ICS).

    • The gall bladder should be located at the 10th-11th ICS, aiding in evaluation.

Ultrasound Grades for Liver Diagnosis

  • Grading System for Liver Appearance:

    • Normal: Bright liver pattern, absence of vessel blurring.

    • Grade 1 (Mild): Bright liver pattern, vessel blurring absent, no marked deep attenuation.

    • Grade 2 (Moderate): Bright liver pattern, presence of vessel blurring, potential diaphragm visibility but blurry.

    • Grade 3 (Severe): Bright liver, significant vessel blurring, marked deep attenuation; diaphragm invisible.

Liver Biopsy Procedures

  • Technique Description:

    • Visuals and steps demonstrating use of a standard tru-cutⓇ instrument to collect biopsy samples from the liver.

  • Histopathology:

    • Evaluation for the number of affected hepatocytes and the presence of macrovacuoles, which indicates abnormal triglyceride levels exceeding clinical thresholds.

    • A triglyceride content above 20% wet weight is considered significant, with samples floating in formalin if above 34%.

Treatment of Fatty Liver

  • Comprehensive Treatment Approach:

    • Treat concurrent underlying diseases.

    • Restore energy balance through dietary management with oral propylene glycol (300 g every 24 hours for 5 days) and optional Vitamin B12 administration.

    • IV bolus of glucose may not always be necessary depending on the clinical presentation.

Preventive Measures in Herd Management

  • Key Guidelines:

    • Conduct regular body condition scoring targeting a score of 3.5/5 at calving.

    • Herd management practices should reflect that more than 10% of the population with scores above 4/5 significantly increases the risk of fatty liver and ketosis.