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ANSC 464 - Companion Animal Nutrition > (T2) Lecture 7b - Nutrient requirements of horses > Flashcards

(T2) Lecture 7b - Nutrient requirements of horses Flashcards

1
Q

What is the definition of a mature horse dependent on?

A

Breed and use
- can reach maturity as early as 2yr, or as late as 6-8yr
- horses reaching 20yr considered “aged”

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2
Q

How do you define maintenance energy requirements?

A

Talking about an ADULT animal, NOT growing or reproducing, and expressing NORMAL activity level within their TNZ.
- 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)

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3
Q

What is the definition of a mature horse?

A

Maturity ~ Skeletal maturity
- growth-plate conversion to bone
- conversion goes from bottom up

OR

Reach 86% of mature body weight at 36 months
- considered mature but that means you are no longer allocating energy for growth

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4
Q

What are 4 factors influencing energy requirements of horses?

A
  1. Breed
  2. Age
    - growth
    - geriatric
  3. Reproduction
    - gestation and lactation
  4. Activity level
    - maintenance
    - exercise

*Some other factors: body composition, environment, disease

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5
Q

What is energy derived from?

A

Macronutrients
1. Starch
2. Fiber
3. Protein
4. Fat

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6
Q

What macronutrient do horses generally consume the most of?

A

FIBER!
- herbivorous species using fiber as an energy source; massive fermentation takes place in intestine

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7
Q

How is MER established/expressed in horses?

A
  • Can be expressed as metabolic BW (BW^0.75 or BW^0.67)
  • In equids, MER varied linearly with BW so there is not an urgent need to use metabolic body weight.
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8
Q

What forms the heat increment?

A
  1. heat of product formation
  2. heat of digestion and absorption
  3. heat of waste formation and excretion
  4. heat of fermentation
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9
Q

What would influence heat of fermentation (HfE)? Aka what macronutrient is associated with an increase in heat increment (heat loss goes up)?

A

Fiber and protein
- lower HI when starch and fat go up in diet
- if we want to increase the horse’s ability to maintain body temp in a colder temp we would increase protein and fiber (increase HI).

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10
Q

What factors influence the energy requirements of horses?

A

Heat production increased with hay vs. mixed diets (grain)
- fermentation
- gut size: more fiber = more fermentation = thicker gut wall = more metabolic tissue

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11
Q

What are five climatic variables that effect energy?

A
  1. ambient temperature
  2. wind velocity
  3. global solar radiation
  4. precipitation
  5. relative humidity

*horse must maintain constant core body temperature

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12
Q

What responses do extreme temperature changes cause?

A

Physiologic, metabolic, and behavioural responses

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13
Q

What are the physiologic, metabolic, and behavioural responses to cold weather?

A
  1. increased eating
  2. increased hair coat
  3. decreased rectal temperature
  4. decreased respiratory rate
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14
Q

What are the physiologic, metabolic, and behavioural responses to hot weather?

A
  1. increased sweating rate
  2. increased respiratory rate
  3. decreased feed intake
  4. increased water intake
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15
Q

How does cold increase eating?

A

Animal needs more energy to stay warm.

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16
Q

Thermoneutral zone

A

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

LCT = -15
UCT = +35

*varies with age, BCS, breed, season, adaptation

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17
Q

How much should DE intake increase for each degree below LCT?

A

DE intake should increase 2.5%
- no established requirements for conditions above UCT

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18
Q

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

A

Below LCT: Add fiber and protein, take out starch and fat

Above UCT: Take out fiber and protein, add starch and fat

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19
Q

What is total body water in adult horses?

A

62-68%
- decreases linearly as horse ages

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20
Q

Can horses tolerate water restriction for extended periods?

A

Yes
- most tolerated with lack of feed
- total lack of water more fatal than lack of feed

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21
Q

When is water balance achieved?

A

If: water loss = water intake

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22
Q

What are 4 reasons for water losses?

A
  1. Fecal losses
    - more loss with hay diets
  2. Urinary losses
    - total loss varies due to diet, fluid availability and metabolic responses to temperature, exercise, and health
  3. Respiratory losses
  4. Cutaneous losses
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23
Q

How can diet influence water loss?

A

High protein diet means more AA need to be deaminated; N bind together in urea and need to be excreted = more water needed to get rid of the extra N from the body.

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24
Q

What are 3 sources of water intake?

A
  1. Direct drinking
  2. Food
    - fresh pasture > hay and grain
    - dependent on amount eaten and dietary composition
  3. Metabolic water
    - produced during oxidation of energy-containing nutrients in the body
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25
Q

What are 3 water requirement guidelines for horses?

A
  1. Body weight is the main determinant of total water intake
  2. Healthy horses readily self-regulate water intake
    - extreme cold can decrease intake
  3. Always access to fresh, clean drinking water
26
Q

How would water intake change if you switched the horse from hay to pasture?

A

Pasture (fresh) grass = would consume less fresh water

Hay = would consume more fresh water

27
Q

What are the protein requirements of a horse?

A
  1. Require individual AA rather than proteins
  2. Horse is sensitive to quality (digestibility) of protein in diet
    - direct correlation btw blood and dietary AAs
    - thought to be little to no nutritional value of added urea or non-protein nitrogen sources
28
Q

What is the first limiting AA for a horse?

A

Lysine

29
Q

Why can you feed ruminants non-protein nitrogen (to meet AA requirements) but potentially not horses?

A
  • Rumens are designed for converting fiberous material into microbial protein and serve as AA source digested in the SI.
  • Monogastrics do not have this system. But what about horses? Some uncertainty how this happens. Hypothesis: protein in the diet can only absorb essential AA in the SI, in the LI the essential AA cannot be absorbed.
30
Q

What contributes to evidence that AA in the hindgut may contribute to homeostasis? (aka does the horse actually absorb some essential AA in the LI).

A
  1. Microbes can use non-protein nitrogen to produce AA
  2. AA transporters in jejunum = expression in the cecum and colon
  3. Maximal lysine transport velocity across the large colon = to jejunum
  4. Free AA detected in colon of humans
31
Q

What is protein digestibility correlated to?

A

Dietary CP content
- increase CP = increase protein digestibility
- prececal digestibility (SI) = ~51%; total tract digestibility = ~79%

32
Q

Why is prececal protein digestibility so low in a horse?

A

Plant based diet and protein = not just free protein, substantial amount bound in the fiber that will only get released in the LI

33
Q

How are protein requirements determined for a horse?

A

Determined through linear and non-linear regression
- increase in N = increase in protein synthesis up to a certain point

34
Q

What are 3 propesed levels of DE energy for a horse at maintenance?

A

Minimum, Average, Elevated
- minimum = -15%
- elevated = +15%

35
Q

How are lysine requirements estimated?

A

Based on dietary Lys content

36
Q

What is a relatively crude way of getting a handle of AA requirements for a horse?

A

Ideal Protein
- based on formulating diet with proper AA rations and amounts
- defined as including the minimum quantity of each AA with maximum utilization of the protein as a whole
- compare all essential AAs to lysine (lys = 100)
- use ratios to estimate requirements for essential AA

37
Q

What happens if a horse experiences a protein deficiency?

A

Deficiency decreases growth, despite adequate energy.
- weight loss in adult horses
- fetal loss in pregnant mares
- decrease milk production in lactating mares
- loss of muscle in exercising horses

38
Q

What happens if a horse consumes excess protein?

A

Excess increases urea
- increases water loss
- decrease growth in young horses
- increase Ca and P loss in weanling horses

39
Q

What would excess protein intake do to water requirements?

A

more protein = more urea loss, no ability to concentrate urea in the urine = have to increase H2O to get rid of nitrogen

40
Q

What is the principal source of energy for horses?

A

Carbohydrates
- fiber, starch, sugars

41
Q

What are some examples of CHO containing feeds?

A

hay, grass, grain

42
Q

How are fiber, starch, sugars (aka CHOs) similar? How are they variable?

A

Contain similar amounts of gross energy. Variable amounts of DE, ME, and NE.

43
Q

What fractioning systems are currently used for carbohydrates? What would be a limitation of these ‘systems’?

A

Non Detergent Fiber (NDF) and Non Fiber CHO (NFC)
- systems only determine total amount of fraction in the diet and don’t say anything about how fast or slow they are digested or absorbed

44
Q

What are the 3 new proposed systems with 3 fractions?

A
  1. Hydrolyzable CHO (CHO-H): digested in SI
  2. Rapidly Fermented CHO (CHO-Fr): readily available for fermentation
  3. Slowly Fermented CHO (CHO-FS): slow fermentation by microbes
45
Q

What can meet up to 50-70% of MER?

A

Cecal VFA production
- up to 70% of MER can come from digesting fiber

Digestion and metabolism of structural CHO may meet MER
- additional energy needed for exercise, growth, lactation, etc.

46
Q

What are fats and fatty acids used for in the diet of a horse?

A

Generally used to increase energy density
- improve energetic efficiency
- enhance body condition
- diminish excitability
- help increase fat oxidation during exercise

47
Q

What are the 2 essential fatty acids for a horse

A
  1. linoleic acid
  2. alpha-linolenic acid
48
Q

How can fat digestibility be increased?

A

With added fats or oils
*does not affect digestibility of other nutrients

49
Q

What are fats used to facilitate absorption of?

A

Vitamins A, D, E, and K , and source of EFA

50
Q

What ratio should calcium and phosphorus be given in?

A

Calcium and phosphorus
~1.4:1

51
Q

Calcium

A
  • 99% found in bones and teeth for strength and rigidity
  • important for muscle contraction, cell membranes, and enzymes
  • homeostasis in blood is critical
52
Q

Phosphorus

A
  • 14-17% found in bone
  • important for energy reactions and synthesis of nucleic acids
53
Q

What dietary factors affect Ca/P absorption? How?

A
  1. Phytates
  2. Oxalates
    - binds divalent cations
    - rich in tropical grasses

Reduce availability

Examples
- napier
- guinea grass
- buffel
- pangola
- millet
- lucern

54
Q

How can minerals be provided to a horse?

A

In a premix or block
- plant based materials are rich in phytate and oxalates that bind minerals and make them inaccessible to the horse

55
Q

What 4 minerals do horses require?

A

Calcium, phosphorous, potassium, sodium

56
Q

Potassium

A
  • major intracellular cation
  • acid base balance
  • osmotic pressure
  • typically met through forages
57
Q

Sodium

A
  • important for CNS, action potentials, transport systems, electrolytes
  • Na and chloride requirements met with supplementation of salt; can provide a salt block
58
Q

What 3 vitamins have hard requirements for horses?

A
  1. Vitamin A
    - important role in night vision
  2. Vitamin D
    - key role in Ca absorption
    - typically met through sunshine
  3. Vitamin E
    - for immune fxn
59
Q

What is a possible mineral toxicity in prairies?

A

Selenium

60
Q

When are horses susceptible to Selenosis?

A

If grazed on high selenium soil

61
Q

What are 3 characteristics of selenium toxicity?

A
  1. corrugated hoof lesions
  2. hoof necrosis
  3. tail alopecia

ANSC 464 - Companion Animal Nutrition (20 decks)

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