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AN SC 464 > 13: Nutrient requirements of horses > Flashcards

13: Nutrient requirements of horses Flashcards

1
Q

What is a mature horse

A

Depends on breed/use
- can reach maturity as early as 2 years, late as 6-8 years
- horses reaching 20 years considered “aged”

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2
Q

What might be a better definition of mature horse

A

Development of skeleton (skeletal maturity)
Growth plate conversion to bone

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3
Q

Why might the definition of considering a horse ‘mature’ when they reach 86% of mature body weight at 36 months be problematic?

A

Growth is still required, so just feeding MER will not allow for growth

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4
Q

Factors that influence energy requirement of horses

A
  • Breed*
  • Age: growth, geriatric
  • Reproduction: gestation and lactation
  • Activity level: maintenance, exercise
  • Environment
  • Sex
  • Muscle mass
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5
Q

Energy is derived from which nutrients? In what proportion would the horse generally consume these nurients?

A

Macronutrients
- starch
- fiber
- protein
- fat

Fiber > starch > protein > fat

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6
Q

Slide 9

A

Look

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7
Q

What is the maintenance energy requirement? Does not include… In horses?

A

Amount of dietary energy needed to prevent change in total energy contained in the body of a horse

Does not include energy needed to support additional activity (gestation, lactation, growth, performance)

MER expressed as BW in horses (not metabolic BW); MER varied linearly

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8
Q

Seven factors of daily heat production

A
  • heat of basal metabolism
  • het of voluntary activity
  • heat of thermal regulation
  • heat of product formation
  • heat of digestion and absorption
  • heat of waste formation and excretion
  • heat of fermentation
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9
Q

Which parts of daily heat production form the “heat increment”

A
  • heat of product formation
  • heat of digestion and absorption
  • heat of waste formation and excretion
  • heat of fermentation
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10
Q

How does diet affect heat increment

A

Go up or down depending on diet (more fiber or protein = goes up, more starch or fat = goes down)
Depending on efficiency of conversion into E of the macronutrients (massive E losses in protein as excess needs to be converted to urea)

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11
Q

Slides 11, 12

A

Heat increment

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12
Q

Daily MER requirement of horses

A

30.3 kcal DE x kg BW

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13
Q

What type of energy is used to calculate horse MER? Why??

A

Digestible energy
It would be more difficult to calculate ME values in horses (would need to collect feces and urine daily)

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14
Q

MER in horses is calculated for… What problems could this cause?

A

Calculated for confined animals, used as minimum or base
Provides a low requirement, not accounting for moderate/regular activity of MER

Calculate average and elevated requirements using 33.3 kcal DE/kg for average (10% increase) and 36.3 kcal DE/kg for elevated (20% increase)

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15
Q

Slide 14

A

Minimum, average and elevated requirements

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16
Q

Five climatic variables that effect energy

A
  • ambient temperature
  • wind velocity
  • global solar radiation
  • precipitation
  • relative humidity
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17
Q

Physiologic, metabolic and behavioural responses to cold vs hot tempertures

A

Cold: increased eating, increased hair coat, decreased rectal temperature, decreased respiratory rate

Heat: increased sweating rate, increased respiratory rate, decreased feed intake (reduce heat increment), increased water intake

18
Q

What is the thermoneutral zone? What affects it/what are the values in horses

A

Metabolic heat production does not need to increase to maintain thermo-stability

Varies wit age, BCS, breed, season, adaption
- lower critical temp = 15C
- upper critical temp = 35C

19
Q

How can feed management help animals cope with hot or cold temperatures?

A

Heat increment
- if it is hot, prepare a diet that has more fat and starch (lower heat production)
- if it is cold add more protein and fiber. Also increase DE intake by 2.5% for each degree below LCT

20
Q

What is the main determinant of water intake in horses? Average maintenance water intake?

A

Body weight

5 L/100kg BW/d (but varies a lot)

21
Q

Four forms of water loss? What is water balance

A
  1. Fecal losses (more loss with hay diets)
  2. Urinary losses (varies due to diet, fluid availability, protein, moisture content of food)
  3. Respiratory losses
  4. Cutaneous losses

when water loss = water intake, water balance = 0

22
Q

Sources of water in horse diet

A
  1. Direct drinking
  2. Food (fresh pasture contains 80% moisture, hay and grain 10-15%): depends on amount eaten and dietary composition
  3. Metabolic water: produced during oxidation of energy-containing nutrients in the body
23
Q

Protein/amino acid requirements

A

Require individual amino acids rather than protein

Lysine first limiting aa

24
Q

Horse is sensitive to what related to protein?

A

Quality of protein in diet

25
Q

Adding urea or non-protein nitrogen sources to horse diets. Why is this different than cows?

A

Little no nutritional value

In ruminants, rumen microbes can convert some non-protein nitrogen back into microbial protein that can be degraded in the SI into individual aa’s
Might be some microbial protein production in horses, but it would be in the LI

26
Q

Slide 22

A

Look

27
Q

How to increase protein digestibility in horses? Why is ileal digestibility so low?

A

Increase CP in diet (add high quality protein sources)

Protein in forage has poor digestibility
Slide 24

28
Q

Slide 26

A

Look

29
Q

Effects of protein deficiency in horses

A
  • Decreased growth
  • Weight loss in adult horses
  • Fetal loss in pregnant mares
  • Decreased milk production in lactating mares
  • Loss of muscle in exercising horses
30
Q

Effects of protein excess in horses

A
  • Increases urea
  • Increases water loss
  • Decreases growth in young horses
  • Increases Ca and P loss in weanlings
31
Q

Principle source of E in horses?

A

Carbohydrates

Look at slide 28, 29

32
Q

What are fats and fatty acids used for in horse diets?

A
  • to increase energy density
  • improve energetic efficiency
  • enhance body condition
  • diminish excitability
  • help increase fat oxidation during exercise
33
Q

Essential fatty acids in horses? Requirements?

A

Linoleic acid and a-linolenic acid

No set requirements

34
Q

Fat digestibility of different sources of fat? How to increase fat digestibility

A

42-49% for forages
55-76% for grains
88-94% for added fats and oils

Increase fat digestibility with added fat or oil

35
Q

Fat is used to facilitate absorption of… and as a source of…

A

Vitamins A, D, E and K (fat soluble vitamins)

And as a source of essential fatty acids

36
Q

Why is calcium required?

A
  • Strength and rigidity of bones and teeth
  • Important for muscle contraction, cell membranes and enzymes
  • Homeostasis in blood is critical
37
Q

Why is phosphorus required? Ideal Ca:P ratio for horses?

A
  • important for energy reactions, and synthesis of nucleic acids

~1.4:1

38
Q

Dietary factors affecting Ca/P absorption? Examples of dietary components?

A

Phytates, oxalates; reduce availability of Ca/P

E.g. napier, guinea grass, pangola

39
Q

Mineral requirements in horses? What are their functions?

A

Potassium: intracellular cation, acid base balance, osmotic pressure

Sodium: CNS, action potentials, transport systems, electrolyte

40
Q

Vitamins required in horses and why

A

Vitamin A: role in night vision

Vitamin D: role in Ca absorption, met through sunshine

Vitamin E: for immune function

AN SC 464 (16 decks)

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