Nutrition in Animal Disease Etiology

• Criteria for assessing nutrition's role in animal disease etiology include dietary deficiency evidence, signs of deficiency in the animal, and whether supplementation prevents or cures the condition.
• Causes of nutritional deficiencies include diet issues, abnormal nutrient absorption or utilization, and unusual nutrient requirements

Dietary Factors

• Body stores of dietary factors can delay the appearance of clinical signs of deficiency.
• Specific deficiencies are linked to soil types.
• Heavy nitrogen fertilizer reduces copper, cobalt, molybdenum, and manganese in pastures.
• Lime application reduces plant copper, cobalt, zinc, and manganese, while increasing molybdenum.
• Drying immature forage preserves vitamin A but may lead to vitamin D deficiency.

Abnormal Absorption

• Excess phosphate decreases calcium absorption.
• Excess calcium decreases iodine absorption.
• Lack of bile salts reduces absorption of fat-soluble vitamins.
• Chronic enteritis diminishes absorption of most dietary essentials.
• Calcium can interfere with the absorption of fluorine, lead, zinc, and cadmium, but also reduces their toxicity.

Abnormal Utilization

• Molybdenum and sulfate impair copper storage.
• Vitamin E can reduce the need for vitamin A.
• Thiamin reduces the requirements for essential fatty acids.

Abnormal Requirements

• Increased requirements due to stimulation of growth, pregnancy and lactation.

Diagnosing Deficiencies

• Clinical signs and necropsy findings from experimental studies are valuable indicators.
• Specific clinical signs and laboratory tests aid in diagnosis like impaired night vision for vitamin A deficiency.
• Radiographic examination is useful for diagnosing rickets.
• Electrocardiographic examination can help diagnose thiamin and vitamin E deficiencies.
• Measuring nutrient levels in blood, urine, and liver can help reveal deficiencies.
• Observing the effects of specific additions to the diet can be a diagnostic test for suspected nutritional deficiencies.
• Poor curative response may be due to inadequate dosage or advanced tissue damage.
• Spontaneous recovery or complications with other factors can occur.
• Preparations used might have pharmacological activity, which can improve the disease without addressing a deficiency.

Energy and Protein Deficiencies

• Energy deficiency is the most common nutritional deficiency affecting the performance of farm animals.
• Causes include inadequate feed amounts, low feed quality or digestibility, insufficient feed supply due to overgrazing, drought, or cost.
• Forage with high water content can limit total energy intake.
• Clinical signs of energy deficiency depend on the animal's age, pregnancy or lactation status, concurrent deficiencies, and environmental factors.

Clinical Signs of Energy Deficiency

• Retarded growth
• Delayed puberty
• Reduced milk production including insufficient colostrum
• Shortened lactation
• Loss of body weight (especially during late pregnancy and early lactation)
• Prolonged anestrus periods affecting reproductive performance
• Prolonged deficiency during late gestation leads to undersized, weak neonates
• Abomasal impaction during cold weather on poor-quality roughage
• Hyperlipemia in fat, pregnant or lactating ponies with declining nutrition
• Sudden energy deficiency in fat, pregnant beef cattle and ewes can result in starvation ketosis and pregnancy toxemia.
• Weakness, recumbency, and death

Protein Deficiency

• Commonly occurs with energy deficiency.
• Clinical signs: reduced appetite, inferior growth rate, lack of muscle development, prolonged time to reach maturity, and decreased milk production.
• Clinical pathology: decreased hemoglobin concentration, PCV, and total serum protein.

Diagnosis

• Relies on clinical signs, estimation of energy and protein concentration in feed, and feed analysis.
• Metabolic profile tests can detect marginal energy and protein deficiencies.

Treatment

• Specific treatment for protein-energy malnutrition in livestock is not usually undertaken due to high costs and prolonged recovery.
• Oral and parenteral fluid and electrolyte therapy can be administered.
• Providing high-quality feeds appropriate to the species is recommended.