Equis ISSN 2398-2977

Musculoskeletal: nutritional deficiencies

Contributor(s): Steve Adair, David Frape, Chris Whitton

Introduction

  • Cause: imbalance in one or more nutrients.
  • Signs: variable - weight loss   Weight loss: overview  , poor performance, lameness, ataxia, developmental orthopedic diseases, eg osteochondrosis   Bone: osteochondrosis  ; skeletal fractures, reduced ability to sweat, growth abnormalities   Hoof: biotin deficiency 02  .
  • Diagnosis: dietary assessment, radiography, blood plasma analysis.
  • Treatment: provide balanced diet appropriate to performance level.
  • Prognosis: depends on degree of pathology, eg degenerative joint changes   Musculoskeletal: osteoarthritis (joint disease)  ; generally good.

Pathogenesis

Etiology

  • Dietary imbalance.

Pathophysiology

Energy
  • Increased energy requirements for increasing level of performance - roughly, 25, 50 and 100% increase necessary for light (pleasure, equitation), medium (stockwork, jumping) and intense (race training, polo) exercise respectively.
  • Excess body fat   →   decreased speed (in humans, 5% increase in bodyweight (BW)    →   4% loss in performance); so small variations in weight carried will affect performance.
  • Restriction of energy intake in obese individuals   →   loss of fat tissue, but also up to 20% of weight loss might involve lean (muscle) tissue   →   loss of strength.
  • Restriction of energy intake in lean individuals   →   up to 50% of weight loss might involve lean (muscle) tissue   →   loss of strength.
  • Regular exercise maximizes fat loss and conserves lean tissue.

Protein

  • Catabolism can contribute to energy used in exercise.
  • Exercise   →   loss of significant amounts of nitrogen in sweat.
  • Also, hard-working horses have higher intake of dry matter   →   increased endogenous fecal nitrogen losses   →   higher protein intake required.
  • No accurate work done on protein requirements of adult horses.
  • 500 kg horse maintenance requirements - 650 g crude protein per day.
  • 500 kg horse in hard work - 1.8 x maintenance requirement.
  • Some evidence that horses recover from exercise faster if on a higher protein diet.
  • Requirement by weight of protein will decrease with increasing quality of protein, measured as lysine and threonine contents of protein.
  • Excess protein intake (>2 g/kg BW per day)   →   decreased water intake and increased urea in urine and plasma; may also decrease glycogen stores; increased urinary nitrogen   →   increased inspired ammonia in stabled horses   →   potential respiratory effects.

Calcium, phosphorus

  • Major bone minerals.
  • Calcium role in muscle contraction.
  • Highest requirements in young growing horses.
  • Adults have constant requirements for remodeling.
  • Daily requirement of 500 kg horse:
    • 30 g Ca for maintenance.
    • 50 g Ca for work.
    • 17 g P for maintenance.
    • 29 g P for work.
  • Imbalanced Ca:P ratio   →   abnormal bone physiology - but exact role in specific developmental orthopedic disorders not known.
  • Minor losses of calcium in sweat.
  • Ideal ratio of Ca:P is at least 1.7:1 to 1.8:1; excess phosphorus   →   decreased calcium absorption.
  • Sources of phosphorus differ in digestibility.
  • Some dietary combinations may promote imbalance:
    • Legume hays - high in calcium.
    • Cereal grains - low in calcium, high in phosphorus.
    • If working horse on high grain diet with some grass hay might   →   excessively high phosphorus and inadequate calcium intakes.
  • Excessive calcium appears to be of less importance, but intake should not exceed requirement by more than 25-35%.
  • Oxalates, phytates in feeds can reduce availability of minerals.
  • Tropical grass hays often high in oxalates.

Electrolytes

  • Role in thermoregulation, fluid balance, acid-base balance, muscle function, osmolarity of fluids.
  • Daily losses via urine, feces, sweat.
  • If diuretics administered - further losses.
  • Increased environmental temperatures, increased exercise   →   increased electrolyte losses.
  • Failure to replace sodium and potassium losses   →   decreased ability to sweat and thermoregulate; decreased food and water intake.

Trace minerals

  • Significance of deficiencies in performance horses not known.
  • Iron, copper and zinc important in hematopoiesis and blood cell metabolism.
  • Low copper or high zinc are related to an increased incidence of osteochondrosis   Bone: osteochondrosis  ; low copper intake is implicated as a causal factor in developmental orthopedic disease.
  • Losses of iron in human athletes exceed intake during training.
  • Most diets apparently more than adequate in iron.
  • Effect of iron supplement on oxygen-carrying capacity of hemoglobin not known - minimal benefit in terms of performance unlikely.
  • Selenium   Selenium  is an internal part of the muscle enzyme glutathione peroxidase. Dietary deficiencies and excesses cause abnormalities.
  • Iodine   Iodine  is required for thyroxine synthesis. Dietary deficiency or excess in the pregnant mare   →    disease in the neonatal foal.

Vitamins

  • Most horse feeds adequate, but old hay is deficient in ß-carotene, artificially-dried hay is deficient in vitamin D2 and silage is deficient in vitamin E   Vitamin E  .
  • Vitamin E   Vitamin E  - biological antioxidant protecting membranes against free radical damage; role in immune function; supplements required to meet recommended intake, but little evidence that increased intake is necessary.
  • B vitamins   Vitamin B1  - from diet or synthesized in hind gut of adult horses in adequate quantities.
  • Some horses have a high requirement for biotin   Biotin  to improve hoof horn structure.

Diagnosis

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Treatment

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Prevention

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Gee E K et al (2000) Changes in liver copper concentration of Thoroughbred foals from birth to 160 days of age and the effect of prenatal copper supplementation of their dams. Aust Vet J 78, 347-353 PubMed.
  • Knight D A et al (1990) The effects of copper supplementation on the prevelance of cartilage lesions in foals. Equ Vet J 22, 426-432 PubMed.
  • Kronfeld D S et al (1990) Dietary aspects of developmental orthopedic conditions in young horses. Vet Clin North Am 6, 451-466 SciDirect.

Other sources of information

  • Frape D (2004) Equine Nutrition and Feeding. 3rd edn. Blackwell Publishing Ltd, UK. ISBN: 1405105984.


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