(T2) Lecture 8a - Nutrient requirements of exercising horses

Question 1

What does moderate exercise with rest cause?

Answer 1

Remodeling of long skeletal bones
- risk of microfractures and injury if intensity increased too rapidly
- full bone turnover takes approximately 6 months

Question 2

What is needed to maintain healthy bone structure?

Answer 2

A reasonable amount of exercise

Question 3

What does RBAE indicate?

Answer 3

measuring mineral density in bone structure

Question 4

Which energy source is used anaerobically and which aerobically?

Answer 4

Anaerobic = glycogen and glucose

Aerobic = all of them, usually fat

Question 5

What 3 fiber types are muscles made of?

Answer 5

1. Type I: Slow-twitch for endurance
   - aerobic
   - oxidize triglycerides
2. Type IIA: Intermediate fast twitch
   - anaerobic + aerobic
   - can use both intramuscular glycogen and triglycerides
3. Type IIX: Fast-twitch for sprints
   - anaerobic
   - low oxidative potential

Question 6

Horses have a sphenic reserve of red blood cells, why?

Answer 6

To increase the oxygen carrying capacity of blood to sustain aerobic energy process as long as possible.

Question 7

What factors affect nutrient/energy requirements of working horses?

Answer 7

1. Duration
2. Intensity
   - speed, ground resistance, incline
3. Other
   - # and height of jumping efforts
   - performance of extended and collected gaits
   - amount of wt carried or pulled

Question 8

Energy requirement for exercising horses

Answer 8

Energy for maintenance + energy for daily exercise effort

Variable depending on:
- horse
- level of training
- type of exercise
- rider wt and experience
- climate
- ground conditions

Question 9

What are the 4 classifications of exercise? Why would they be used?

Answer 9

Light, Moderate, Heavy, Very Heavy

Trying to put a number on energy needs for exercise.

Question 10

How can energy requirements be estimated from oxygen utilization? What is heart rate associated with?

Answer 10

Increase HR = Increase O2 = Increase energy use

Question 11

How do energy requirements for exercise vary depending on exercise category?

Answer 11

For very heavy work there is a slightly greater maintenance requirement correcting for the increasing intensity and duration of exercise.

Question 12

Carbohydrates for exercising horses

Answer 12

• Important source of energy!!!!
• Increased intensity = increased CHO use
• due to recruitment of fast-twitch muscle fibers (anaerobic)
• muscle glycogen depletion related to exercise intensity and duration
• must maintain adequate availability bc fatigue resistance is reduced when glycogen is depleted

Question 13

What feed types would replenish glycogen faster?

Answer 13

Rapidly digestible CHOs (starch and sugars)
- we also try to have as much fat oxidation as possible so we want adipose tissue; better the horse is at beta-oxidation to support exercise the longer muscle glycogen will be maintained and the longer the horse will be able to run

Question 14

Linoleic acid forms ________________
Alpha-Linolenic forms ________________

Answer 14

1. arachidonic acid
2. EPA and DHA

Question 15

Do horses require arachidonic acid?

Answer 15

No, they can make it themselves

Question 16

What is protein metabolism estimated to be during exercise?

Answer 16

Only 5-15% of energy expenditure
- serum concentrations of branched-chain AA are reduced after prolonged exercise (oxidized for energy)
- no proven detrimental effects of high protein intake on performance

Question 17

When do exercising horses require increased protein and AA?

Answer 17

For developing and repairing muscles; need an ideal AA profile for muscle repair

CP increases for exercises depending on category

If protein req goes up, so does lysine

Question 18

What are calcium, phosphorus, and magnesium required for?

Answer 18

Bone development
- increased requirement met through additional feed for energy
- must be accompanied by exercise for metabolism

Question 19

How does the link between mineral requirement and exercise work?

Answer 19

More energy used = more minerals being used

Question 20

Why do requirements for potassium, sodium and chloride increase in exercising horses?

Answer 20

To replace loss in sweat.
- requirement is adjusted upwards with an increased intensity of exercise

Question 21

Why are there so many vitamin supplements on the market if there are no clear requirements established for working horses?

Answer 21

Owners looking for easy fix for their horse to run faster

Question 22

Water requirements for exercising horses

Answer 22

Dependent on conditions and duration

Intake can increase x2-3 over maintenance

Question 23

4 Disorders Associated with Exercise

Answer 23

1. Gastric Ulcers
2. Post Exhaustion Syndrome
3. Exertional Rhabdomyloysis Syndrome
4. Polysaccharide Storage Myopathy

Question 24

Gastric Ulcers

Answer 24

Erosion of the squamous mucosa due to exposure to gastric acid, reduces appetite.

Causes
- contracted stomach
- continuous HCl secretions
- contraction of abdominal muscles
- high rapidly digestible CHO meals
- fasting and amylolytic bacteria

Question 25

How would you prevent or treat a horse with gastric ulcers using dietary changes?

Answer 25

1. reduce exercise 2. let horse graze = increase forage = increase chewing and saliva = supporting recover of stomach wall 3. take away concentrate

Question 26

Post Exhaustion Syndrome

Answer 26

Very severe muscle damage resulting in muscle stiffness and reluctance to move post-exercise. Cause - muscular accumulation of lactate, depletion of glycogen = severe anaerobic metabolas Prevention - electrolytes - calcium carbonate - increase conditioning - slow down after heavy exercise - IV

Question 27

Exertional Rhabdomylosis Syndrome

Answer 27

Muscle pain and cramping during or immediately after exercise, can be sporadic or chronic Diagnosis - myogloburia (muscle material in urine) - creatinine kinase - lactate dehydrogenase - aspartate aminotransferase Cause - overtraining, deficiencies in vit E and selenium - can be recurrent

Question 28

Polysaccharide Storage Myopathy

Answer 28

Genetic disorder of PSSM1 or PSSM2 Cause - high concentrations of glycogen and glucose-6-phosphate in muscles Signs - exercise intolerance - muscle stiffness/pain - lameness - camped-out stance - colic symptoms - muscle atrophy

Question 29

How can you prevent polysaccharide storage myopathy?

Answer 29

Want to prevent glycogen buildup = feed less starch and sugar, more fiber, and use FAT as an energy source. - remove concentrates - implement daily exercise regimen

Question 30

Feeding behaviour of horses

Answer 30

- graze continuously - do not adjust food intake to diet energy density (seasonal pattern) - voluntary intake greatly distorted by palatability (alfalfa > grass hay) - highly selective eaters (preference for what is known)

Question 31

What is group feeding affected by?

Answer 31

1. social status 2. variation in appetites 3. intake rates Creates aggressive behaviour with limited feed provisions; may require separation into different groups.

Question 32

What is grazing time affected by?

Answer 32

Environment - seasonal eating - rain, wind, high temps decrease grazing - high humidity increases grazing - snow cover can influence grazing - seeking shelter - infestation of insects

Question 33

Anorexia

Answer 33

- typically indicative of an illness (link btw immune system and brain = cytokines) - may be caused by dental problems - can be a learned behaviour (typically limited)

Question 34

Coprophagy

Answer 34

- not normal behaviour in horses - will not graze in areas contaminated with feces - exception: foals consume dams feces to establish healthy microbiome

Question 35

Geophagia

Answer 35

Dirt-eating - not uncommon - may be used to acquire salt and trace minerals - sand may create colic or diarrhea

Question 36

Wood chewing

Answer 36

- undecided if normal or predecessor to cribbing - may cause intestinal obstruction - typically caused by inclement weather or lack of fiber - horse may be stressed, attention seeking, or not getting enough opportunities to graze

Question 37

3 Stereotypic Behaviours of Horses

Answer 37

1. Cribbing - incisor teeth grip object, horse pulls back and gulps air - associated with drop in stomach pH and incidence of gastric ulcers 2. Stall-walking - constant movement in circles around an enclosed stall 3. Waving - shifting wt while stationary

Question 38

Why may forage alleviate stereotypic behaviour?

Answer 38

Add more fiber (bulk) to diet to reduce energy density - animal spends more time eating and prolonged satiety