Enteral/Parenteral Nutrition in Foals and Adult Horses VCNA

How long can a healthy, adult horse tolerate food deprivation (protein/calorie malnutrition [PCM] or simple starvation) for with few systemic effects?

72 hours

Glucose Sources During Starvation

During the first hours to days of starvation, glycogen stores are used from various tissues (liver, kidney, muscle) for glucose production

As glucose becomes limited, many body tissues begin to rely on fatty acid oxidation and the production of ketone bodies as energy sources

Glycerol produced from lipid degradation, lactate from the Krebs cycle, and amino acids provided from muscle tissue breakdown continue to be used for gluconeogenesis to provide energy to glucose-dependent tissues (CNS and RBCs)

This response to starvation correlates with an increase in circulating levels of growth hormone, glucagon, epinephrine, leptin, and cortisol and a decrease in insulin and thyroid hormones

Hunger Drive and Metabolism in Protein/Calorie Malnutrition

There is an increased drive to eat and a decrease in energy expenditure

Metabolism slows in an effort to conserve body fuels, and the body survives primarily on fat stores, sparing lean tissue until such a time as refeeding occurs

Response to Protein/Calorie Malnutrition in the Neonate

The healthy newborn foal should have neough liver glycogen to support energy needs for several hours of life

Glycogen stores at birth can vary significantly with illness or prematurity

Lack of nutritional reserves can result in hypoglycemia and hypothermia and quickly affect the ability to maintain normal function and behavior

Metabolic Response to Injury in the Horse

The metabolic response to injury is characterized by an increased metabolism and the onset of a catabolic process leading to excessive breakdown of tissue proteins, which are used as metabolic fuel

Insulin resistance develops and hyperglycemia may occur despite the absence of food intake

Designed to provide endogenous substrates for gluconeogenesis, wound healing, immune cell replication, and synthesis of acute phase

Long-term muscle breakdown results in loss of muscle strength, visceral orang dysfunction secondary to loss of structural and enzymatic proteins, impaired wound healing, immunosuppression, and compromise to overall health

Effects of Nutritional Response to Catabolic State

Nutritional supplementation will reverse the catabolic processes occurring during simple starvation, but will not completely reverse those occurring during metabolic stress because as long as tissue injury persists, catabolic processes are maintained

Goals of Nutritional Support in Critical Illness

Save life

Maintain muscle mass

Preserve and improve cellular and tissue function

Speed recovery

Indications for Nutritional Support

Patients with an increased metabolic rate (young growing animals), a history of malnutrition or hypophagia, underlying metabolic abnormalities that could worsen with food deprivation (equine metabolic syndrome, hyperlipidemia), and disorders such as severe trauma, sepsis, burns, or strangulating bowel obstruction that result in an increased energy demand

Underweight horses require nutritional support earlier

Obese or overconditions individuals, particularly pony breeds, miniature horses, and donkeys, individuals with Cushings or EMS, and pregnant or lactating mares are at risk for hyperlipidemia and should receivenutritional support to try to prevent or minimize hyperlipidemia

Benefits of Enteral Feeding

Provides most of the nutrition to the gut

Has been shown to improve gut barrier integrity, gut mass, protein content, gut motility, and function

Metabolic Needs of Sick Patients

May fall more closely within the range of the resting to maintenance energy requirements or normal healthy individuals

• Exceptions are individuals with extreme trauma, burns or severe sepsis, surgical conditions that require intestinal resection, and large areas of devitalized tissue (eg clostridial myositis patients that undergo multiple fasciotomy procedures)

Resting Energy Requirements

The amount of energy needed to maintain an individual (no weight gain or loss) in a thermoneutral environment without the metabolic demands of digestion

Maintenance Energy Requirements

The amount of energy needed to maintain an individual (no weight gain or loss) in a thermoneutral environment with the metabolic demands of digestion

What % higher than resting energy requirements are maintenance energy requirements?

About 30%

Estimate for Resting Energy Requirement

22-23 kcal/kg/day for the average full sized horse

Estimate for Maintenance Energy Requirement

30-35 kcal/kg/day

Protein Requirement of the Healthy Adult Horse

0.5-1.5 g/kg/day

Protein Requirement for the Growing Foal

7 g/kg/day

Lysine requirements of growing horses are higher than for mature horses

Protein Considerations in Critically Ill Horses

During critical illness or severe injury, protein catabolism and utilization of amino acids as a source of fuel continue despite the presence of energy stores so recommended to provide the higher end of the estimated need

Supplementation of nonessential amino acids that may improve the outcome in illness

• Glutamine supplementation has been shown to improve clinical outcome

  • Used as a fuel for enterocytes and other rapidly dividing cells

• Branched chain amino acids and arginine supplementation

  • Arginine is a precursor to nitric oxide, is an important vasodilating agent, upregulates immune function and secretion of several hormones, and may reduce ischemia-reperfusion injury

Advantages of Complete Pelleted Feeds

Relatively inexpensive and well balanced for the maintenance requirements of an adult horse

Contain fiber, which is beneficial for intestinal motility, increasing colonic blood flow, enzymatic activity, and colonic mucosal cell growth and absorption

Disadvantages of Complete Pelleted Feeds

Difficulty involved in giving them via NG intubation

Disadvantages of Powdered Commercial Diets

Cost over complete pelleted diets

Associations with Liquid Diets in Horses

Studies in healthy horses have found that the feeding of liquid diets is associated with decreased intestinal transit time and decreased prececal starch and fat digestion

• Avoid high starch (>25% DE) and high fat (>6% DE) diets

• Use highly digestible carbohydrate sources (processed corn starch

Similarities between Mare’s and Goat’s Milk

The major whey protein in both goat’s and mare’s milk is B-lactoglobulin

• The major whey protein in cow’s milk is a-lactoglobulin

Recommendations for Milk Replacer for Foals

Choose a replacer that is developed for foals rather than all-species

Use replacers that contain whey protein rather than other protein sources because of digestibility concerns

Provide a source of fresh water as they are much higher in salt than natural mare’s milk and hypernatremia can develop if a water source is not provided

Metabolic Demands of a Sick Neonates

5-10% of its bodyweight (500-100 kcal/kg/d)

Advantages of Parenteral Nutrition

Ability to supply nutrition when the enteral route is unavailable

Ability to tailor the types of nutrition provided for each individual animal

Decreases weight loss, particularly lean body mass, and improves wound healing, immune function, and outcome in human and animal studies when the enteral route cannot be used

Candidates for Parenteral Nutrition

In the adult horse, to supply partial nutrition when oral intake is insufficient or the oral route cannot be used

Individuals that are recumbent or dysphagic, have GI disease, or have pre-existing protein/calorie malnutrition

Disadvantages of Parenteral Nutrition

Expense

Loss of the beneficial effect of enteral nutrition on maintaining the gut function and mass

What are carbohydrates and lipids used for in parenteral nutrition?

To meet the horse’s energy needs

What are amino acids used for in parenteral nutrition?

Wound healing, immune function, and muscle maintenance

What are lipids for parenteral nutrition composed of?

Come in 10%, 20%, and 30% emulsion

Composed primarily of soybean oil (or safflower), egg yolk phospholipids, and glycerin

When should lipids be added to the parenteral nutrition solution?

Last, to avoid destabilization of the emulsion because of an acidic environment

What % of nonprotein calories can lipids provide in parenteral nutrition?

Up to 30-60% of the nonprotein calories

When is adding lipids to parenteral nutrition beneficial?

In patients with persistent hyperglycemia or hypercapnia, reducing dependency on glucose as the principal energy source

When should lipids be avoided in parenteral nutrition?

In horses with known hyperlipidemia or in horses suspected of being lipid intolerant

• Lipid intolerance can be seen in patients with systemic inflammation, sepsis, or underlying metabolic derangements

What should the ratio of nonprotein calories (NPC) to nitrogen be in the final solution?

At least 100:1 to limit the use of protein as an energy source

Parenteral Nutrition Recipe for a Neonatal Foal

Adult Horse Parenteral Nutrition Recipe

What are additional components that can be added to parenteral nutrition or given separately to supplement?

Electrolyte solutions and vitamin and mineral supplements

• Recommended to supplement water-soluble B vitamins daily as deficiencies can exacerbate problems associated with refeeding

• Some vitamins are best given orally (vitamins C and E) or added to separate crystalloid solutions (B vitamins)

• Fat-soluble vitamins suchs ad E, D, and A are stored in body tissue so they are generally not supplemented unless an individual is off feed for a prolonged period or has an illness that may result in greater use or need

  • Antioxidant benefits of vitamin E may make it worth providing oral supplementation in early illness

• Minerals, if required, are best supplemented in separate crystalloid solutions, as divalent cations may destabilize lipid emulsions

Infusion Rate for Parenteral Nutrition

Generally start with an infusion rate targeting approximately 25% of the calculated goal

If blood glucose concentrations are within reference ranges, then the rate can be increased by an additional 25% every 4-8 hours

Complications Associated with Hyperglycemia

Hyperglycemia both at admission and during hospitalization has been associated with an increased risk of complications including infections and renal failure, longer hospital stays, and reduced survival in humans and horses with critical illness or injury

Insulin Therapy in Response to Hyperglycemia

Complications Associated with Lipid Infusions

Lipid infusions have been associated with allergic reactions, hyperlipidemia, alterations in liver function, and fat embolism

• The risk of fat embolism is higher in larger droplet emulsions or in emulsions that have been stored too long and have begun to destabilize

Thrombocytopenia, coagulopathy, fat embolization ,thrombocytopenia, and alterations in cellular immunity are reported with lipid infusions

Triglyceride levels and platelet counts should be monitored regularly when lipids are added to parenteral nutrition solutions

Complications Associated with Parenteral Nutrition

Hyperammonemia and elevations in serum urea nitrogen level from excess protein catabolism, hypercapnia caused by excess carbohydrate metabolism, thrombophlebitis caused by hypertonicity and pulmonary embolism (thought to be caused by destabilized lipid emulsions), and sepsis