(T2) Lecture 8a - Nutrient requirements of exercising horses Flashcards
What does moderate exercise with rest cause?
Remodeling of long skeletal bones
- risk of microfractures and injury if intensity increased too rapidly
- full bone turnover takes approximately 6 months
What is needed to maintain healthy bone structure?
A reasonable amount of exercise
What does RBAE indicate?
measuring mineral density in bone structure
Which energy source is used anaerobically and which aerobically?
Anaerobic = glycogen and glucose
Aerobic = all of them, usually fat
What 3 fiber types are muscles made of?
- Type I: Slow-twitch for endurance
- aerobic
- oxidize triglycerides - Type IIA: Intermediate fast twitch
- anaerobic + aerobic
- can use both intramuscular glycogen and triglycerides - Type IIX: Fast-twitch for sprints
- anaerobic
- low oxidative potential
Horses have a sphenic reserve of red blood cells, why?
To increase the oxygen carrying capacity of blood to sustain aerobic energy process as long as possible.
What factors affect nutrient/energy requirements of working horses?
- Duration
- Intensity
- speed, ground resistance, incline - Other
- # and height of jumping efforts
- performance of extended and collected gaits
- amount of wt carried or pulled
Energy requirement for exercising horses
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
What are the 4 classifications of exercise? Why would they be used?
Light, Moderate, Heavy, Very Heavy
Trying to put a number on energy needs for exercise.
How can energy requirements be estimated from oxygen utilization? What is heart rate associated with?
Increase HR = Increase O2 = Increase energy use
How do energy requirements for exercise vary depending on exercise category?
For very heavy work there is a slightly greater maintenance requirement correcting for the increasing intensity and duration of exercise.
Carbohydrates for exercising horses
- 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
What feed types would replenish glycogen faster?
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
Linoleic acid forms ________________
Alpha-Linolenic forms ________________
- arachidonic acid
- EPA and DHA
Do horses require arachidonic acid?
No, they can make it themselves
What is protein metabolism estimated to be during exercise?
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
When do exercising horses require increased protein and AA?
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
What are calcium, phosphorus, and magnesium required for?
Bone development
- increased requirement met through additional feed for energy
- must be accompanied by exercise for metabolism
How does the link between mineral requirement and exercise work?
More energy used = more minerals being used
Why do requirements for potassium, sodium and chloride increase in exercising horses?
To replace loss in sweat.
- requirement is adjusted upwards with an increased intensity of exercise
Why are there so many vitamin supplements on the market if there are no clear requirements established for working horses?
Owners looking for easy fix for their horse to run faster
Water requirements for exercising horses
Dependent on conditions and duration
Intake can increase x2-3 over maintenance
4 Disorders Associated with Exercise
- Gastric Ulcers
- Post Exhaustion Syndrome
- Exertional Rhabdomyloysis Syndrome
- Polysaccharide Storage Myopathy
Gastric Ulcers
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
How would you prevent or treat a horse with gastric ulcers using dietary changes?
- reduce exercise
- let horse graze = increase forage = increase chewing and saliva = supporting recover of stomach wall
- take away concentrate
Post Exhaustion Syndrome
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
Exertional Rhabdomylosis Syndrome
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
Polysaccharide Storage Myopathy
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
How can you prevent polysaccharide storage myopathy?
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
Feeding behaviour of horses
- 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)
What is group feeding affected by?
- social status
- variation in appetites
- intake rates
Creates aggressive behaviour with limited feed provisions; may require separation into different groups.
What is grazing time affected by?
Environment
- seasonal eating
- rain, wind, high temps decrease grazing
- high humidity increases grazing
- snow cover can influence grazing
- seeking shelter
- infestation of insects
Anorexia
- 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)
Coprophagy
- not normal behaviour in horses
- will not graze in areas contaminated with feces
- exception: foals consume dams feces to establish healthy microbiome
Geophagia
Dirt-eating
- not uncommon
- may be used to acquire salt and trace minerals
- sand may create colic or diarrhea
Wood chewing
- 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
3 Stereotypic Behaviours of Horses
- Cribbing
- incisor teeth grip object, horse pulls back and gulps air
- associated with drop in stomach pH and incidence of gastric ulcers - Stall-walking
- constant movement in circles around an enclosed stall - Waving
- shifting wt while stationary
Why may forage alleviate stereotypic behaviour?
Add more fiber (bulk) to diet to reduce energy density
- animal spends more time eating and prolonged satiety
