Vitamin E and Immune Function in Horses

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Vitamin E and Immune Function in Horses

• Paul D. Siciliano, Ph.D.
• Dept. of Animal Sciences

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Vitamin E and Immune Function
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Overview

• Brief review of immunology
• General overview of vitamin E
• Vitamin E requirements of horses
• Effect of vitamin E on immune function in horses
• Immunostimulatory mechanisms of vitamin E
• Practical applications

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Review of Immunology
Categories of Immune Response
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Review of Immunology

• Three stages of the immune response
• Cognitive Phase (Induction)
• Amplification
• Effector Phase

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Review of Immunology

• The immune system generates pro-oxidants,
  potentially contributing to oxidative stress if
  left unchecked
• Part of normal metabolism
• Used as a defense mechanism

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Review of Immunology

• Reactive oxygen species produced as a part of
  normal metabolism

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Review of Immunology
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Review of Immunology

• Reactive oxygen species produced as a defense
  mechanism
• Oxidative burst
• Neutrophils and macrophages
• Produce superoxide, hydrogen peroxide and
  hypochlorite
• Bactericidal agents

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Review of ImmunologyOxidative Burst
NADPH Oxidase
bacteria
O2-?
NADP
Neutrophil/Macrophage Phagocytosis
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Cellular Antioxidant Defense Mechanisms
Cell Membrane
Reactive Oxygen Species
Lipid Oxidation
Cytosol
Hydrogen peroxide
Superoxide
Water
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Overview

• Brief review of immunology
• General overview of vitamin E
• Vitamin E requirements of horses
• Effect of vitamin E on immune function in horses
• Immunostimulatory mechanisms of vitamin E
• Practical applications

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Overview of Vitamin E

• Major Lipid Soluble Antioxidant
• Vitamin E containing compounds
• 4 tocopherols (alpha, beta, gamma, delta)
• 4 tocotrienols (alpha, beta, gamma, delta)

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RRR-Alpha-tocopherol
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Overview of Vitamin E
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Overview of Vitamin E
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Overview

• Brief review of immunology
• General overview of vitamin E
• Vitamin E requirements of horses
• Effect of vitamin E on immune function in horses
• Immunostimulatory mechanisms of vitamin E
• Practical applications

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Vitamin E Requirements of Horses

• Present requirements (NRC, 1989)
• Maintenance 50 IU/kg DM
• All others 80 IU/kg DM
• Past requirements
• NRC (1973) req. not established
• NRC (1978) 15 IU/kg DM

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Vitamin E Requirements of Horses

• Work contributing to the current requirement
• Estimates from depletion-repletion-depletion
  study (Roneus et al., 1986)
• Clinical signs of capture myopathy in Przewalski
  horses and zebra alleviated (NRC, 1989).
• Improved humoral immune response (Baalsrud and
  Overnes, 1986)

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Vitamin E Requirements of Horses

• Estimates from depletion-repletion-depletion
  study (Roneus et al., 1986)
• Mature idle Standardbreds
• 400 to 460 kg BW
• 2.5 mo depletion period (Basal diet 107 IU/d)
• Five Dietary Treatments (112 d n3/trt)
• Control (basal diet 107 IU/d)
• Basal 200 IU/d (switched to 5,400 IU/d at 2mo)
• Basal 600 IU/d
• Basal 1,800 IU/d
• Basal 5,400 IU/d
• 51-d depletion period

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Vitamin E Requirements of Horses

• Conclusions (Roneus et al., 1986)
• Optimization of tissue concentrations require
• 600 to 1,800 IU/d
• 70 to 209 IU/kg DM
• Assumes 430 kg BW DMI 2 BW

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Vitamin E Requirements of Horses
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Vitamin E Requirements of Horses

• Work contributing to the current requirement
• Estimates from depletion-repletion-depletion
  study (Roneus et al., 1986)
• Clinical signs of capture myopathy in Przewalski
  horses and zebra alleviated (NRC, 1989).
• Improved humoral immune response (Baalsrud and
  Overnes, 1986)

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Vitamin E Requirements of Horses

• Clinical signs of capture myopathy in Przewalski
  horses and zebra alleviated (NRC, 1989).
• Clinical signs (temporary to persistent muscle
  soreness and lameness) w/ diets containing 50
  IU/kg DM
• Clinical signs absent when fed diet containing
  100 IU/kg DM

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Vitamin E Requirements of Horses

• Information is limited and different criteria of
  adequacy support different conclusions,
  establishing a single minimum requirement for
  vitamin E is difficult.
• (NRC, 1989)

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Vitamin E Requirements of Horses

• One criterion that has not been examined in the
  horse in sufficient detail is the amount of
  vitamin E required for optimum immune function
• (NRC, 1989)

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Vitamin E Requirements of Horses

• Work contributing to the current requirement
• Estimates from depletion-repletion-depletion
  study (Roneus et al., 1986)
• Clinical signs of capture myopathy in Przewalski
  horses and zebra alleviated (NRC, 1989).
• Improved humoral immune response (Baalsrud and
  Overnes, 1986)

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Vitamin E Requirements of Horses

• Improved humoral immune response (Baalsrud and
  Overnes, 1986)
• Mature idle horses (600 kg BW)
• 4 Treatments for 168 d
• Control (18 IU E/kg DM 0.03 ppm DM Se) n4
• Vit. E (80 IU E/kg DM 0.03 ppm DM Se) n4
• Se (18 IU E/kg DM 0.5 ppm DM Se) n3
• Vit. E Se (80 IU E/kg DM 0.5 ppm DM Se) n4
• Vaccinated for influenza equi 1 2 and tetanus
  following 84 d of dietary treatment

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Vitamin E Requirements of Horses

• Improved humoral immune response (Baalsrud and
  Overnes, 1986)
• Vit. E or Vit. E Se resulted in greater
  antibody titers against influenza equi type 1 and
  2 as compared to Ctrl or Se
• No trt difference for tetanus

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Vitamin E and Immune Function in Horses

• Improved humoral immune response (Baalsrud and
  Overnes, 1986)
• Limitations
• Small number of horses/trt
• Inconsistent results between tetanus and
  influenza titer response
• Still provides evidence of an immunostimulatory
  effect of vitamin E

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Vitamin E and Immune Function in Horses

• Effect of E on mare colostrum immunoglobin
  concentration
• (Hoffman et al., 1999)
• Previous observation
• Mares suppl. w/ corn oil had 4.2 fold increase in
  colostrum IgG
• Hypothesized high E of corn oil (327 IU/kg)
  contributed to the effect

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Vitamin E and Immune Function in Horses

• Effect of E on mare colostrum immunoglobin
  concentration
• (Hoffman et al., 1999)
• 12 pregnant mares (TB and Morgan)
• Fed 80 vs 160 IU E/kg DM (n6/trt)
• 28 d prior to foaling
• 28 d post foaling

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Vitamin E and Immune Function in Horses

• Effect of E on mare colostrum immunoglobin
  concentration
• (Hoffman et al., 1999)
• Pre-suckled colostrum IgG concentration greater
  in mares fed 160 IU E/kg DM
• Tendency for greater serum IgG in foals suckling
  mares fed 160 IU E/kg DM

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Vitamin E and Immune Function in Horses

• Conclusions
• Some evidence for an immunostimulatory effect
  exists
• Specific dietary recommendations are not clear
  and require further clarification

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Overview

• Brief review of immunology
• General overview of vitamin E
• Vitamin E requirements of horses
• Effect of vitamin E on immune function in horses
• Immunostimulatory mechanisms of vitamin E
• Practical applications

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Immunostimulatory mechanisms of vitamin E

• Possible mechanisms
• Maintenance of cell membrane integrity

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Immunostimulatory mechanisms of vitamin E

• Possible mechanisms
• Maintenance of cell membrane integrity
• Effects on cell signal transduction
• E influences IL2 production
• IL2 critical for T cell proliferation and
  differentiation

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Immunostimulatory mechanisms of vitamin E

• Possible mechanisms
• Maintenance of cell membrane integrity
• Effects on cell signal transduction
• E influences IL2 production
• IL2 critical for T cell proliferation and
  differentiation
• Reduction of immunosuppressive PGE2
• PGE2 can inhibit T cell activation
• E can inhibit cyclooxygenase (rate limiting step
  in PGE2 synthesis

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Overview

• Brief review of immunology
• General overview of vitamin E
• Vitamin E requirements of horses
• Effect of vitamin E on immune function in horses
• Immunostimulatory mechanisms of vitamin E
• Practical applications

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Practical Applications

• Situations challenging the immune system
• Neonate
• Intense exercise
• Transport
• Old age
• Close confinement housing

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Practical Applications

• Recommendations?
• Limited information
• Confined to mature idle horses, broodmares and
  foals
• Available evidence suggests wide range
• 80 to 160 IU E/kg DM
• Consequences of over-supplementation?

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