5a Nutrient Requirements of Horses 2 Flashcards
How much body weight do horses carry on their front limbs?
60-65%
What are the 3 muscle fibre types and what are they for?
type 1: slow twitch for endurance; beta oxidation of fat
type 2A and 2X: fast twitch for sprint; glucose
Describe the respiration rate during gallop?
1 breath: 1 stride
Why would horses require a reserve of red blood cells?
- blood cells can be released from the spleen during exercise
- higher capacity to carry oxygen, more oxygen to muscles
- natural blood doping
How does exercise affect bones?
- remodelling of long skeletal bones
- risk of micro fractures and injury if intensity increased too rapidly
- full bone turnover takes approximately 6 months
- bone tissue becomes more active and as a result, reduction in bone density
What factors affect exercise?
- duration
- intensity (speed, ground resistance, incline)
- other (number and height of jumping efforts, performance of extended and collected gaits, amount of weight carried or pulled)
Describe the energy requirement of exercising horses?
- energy for maintenance + energy for daily exercise effort
- variable depending on: horse, level of training, type of exercise, rider weight and experience, climate, ground conditions)
Describe the ‘light’ exercise category.
- 1-3 hours/week
- recreational riding
Describe the ‘moderate’ exercise category.
- 3-5 hours/week
- school horses, polo, ranch work
Describe the ‘heavy’ category of work.
- 4-5 hours/week
- frequent show horses, race training
Describe the ‘very heavy’ category of work.
- ranges from 1hr/week of speed work to 6-12hr/week of slow work
- racing, elite 3 day event
What is oxygen utilization closely related to, and what is it used to measure?
- closed related to heart rate
- used to measure energy expenditure
- linearly related to speed
What does oxygen utilization for account for at high heart rates?
- does not account for anaerobic energy
Describe the relationship between heart rate, oxygen utilization and energy utilization.
- HR increases linearly
- exponential increases in oxygen utilization and energy utilization
What are the energy requirement equations for each level of exercise?
- light work: DE = (0.0333 x BW) x 1.3
- moderate: DE = (0.0333 x BW) x 1.4
- heavy: DE = (0.333 x BW) x 1.6
- very heavy: DE = (0.0363 x BW) x 1.9
Why does carb use increase as exercise intensity increases?
- recruitment of fast twitch muscle fibres
Where are carbohydrates derived from during exercise?
- muscle glycogen, blood glucose, hepatic glycogenolysis or hepatic gluconeogenesis
- muscle glycogen depletion related to exercise intensity and duration
Does ‘carb loading’ work in horses?
- muscles have a certain capacity to capture glycogen so only works to a certain extent
At 68 hr post exercise, what percentage of muscle glycogen is replenished?
- 85%
- more desirable to enhance fat utilization and spare glycogen
What feed types would replenish glycogen faster?
- starch digested as glucose
- grains like oats or sugar
How is fat supplementation believed to affect glucose?
- glucose sparing effect
- response may only occur during low and moderate exercise
- requires 2-3 months for full adaptation
- true effects undetermined
What is another name for omega 6 fatty acids and what does it form?
- linoleic acid
- arachidonic acid
What is another name for omega 3 fatty acid and what does it form?
- alpha-linolenic acid
- forms EPA and DHA
What are some of the beneficial responses of supplementation of EPA and DHA?
- alters cell membrane of platelets, erythrocytes, neutrophils and monocytes
- increase fluidity of red blood cells
- decrease inflammatory response
- reduction in omega 6 and increase in omega 3 related to decrease in prostaglandins and dampening of inflammation
How does exercise affect plasma concentrations of branched chain AA?
- increases it
- oxidized for energy
Are there any detrimental effects of high protein intake on performance?
- none proven
- may reduce glycogen
- may excess capacity of urea cycle
Why does exercise require increased protein?
- developing and repairing muscle
- must also account for N loss in sweat
What is the lysine requirement?
4.3 x CP requirement
What is the importance of calcium, phosphorous and magnesium in exercise?
- all required for bone development
- increased requirement met through additional feed for energy
- must be accompanied by exercise for metabolism
What is the role of potassium, sodium and chloride in exercise?
- increased requirements to replace loss in swear
- met through increased intake to meet energy requirements
- can provide electrolyte supplement if necessary
What vitamin requirements are there for working horses?
- none…
- most likely met through increased feed intake
Water can account for what percentage of body weight loss during performance?
3.6-7.7%
How does sweat change in a dry versus humid environment?
hot, dry: 1.5L/100kg BW
hot, humid: 2-2.5L/100kg BW
How does water intake change with exercise?
- can increase 2-3 fold over maintenance requirement
- ranges from 36-92L per day
What are 4 disorders associated with exercise?
- gastric ulcers
- post exhaustion syndrome
- exertional rhabdomyolysis syndrome
- polysaccharide storage myopathy
Describe gastric ulcers.
- erosion (lesions) of the squamous mucosa
- due to exposure to gastric acid, undissociated VFA
- reduces appetit, causes pain after eating
- effects 40-90% of performance horses
- raises to 100% in actively racing TB
- prevention: decrease size of carb meals, more grazing, lower starch, higher oil/fiber
Describe post exhaustion syndrome.
- muscle stiffness occurring 2-4 days after exercise
- causes reluctance to move
- due to muscular accumulation of lactate, depletion of glycogen
- prevention: add electrolytes, feed calcium carbonate, alter training t increase conditioning, adequate slow cool down, administer IV
Describe exertional rhabdomyolysis syndrome.
- muscle pain and cramping associated with exercise
- can be sporadic or chronic
- occurs during or immediately after exercise
- in TB, associated with defect in intercellular calcium regulation
- prevention: reduce dietary starch, increase dietary fat
Describe polysaccharide storage myopathy.
- characterized by high concentrations of glycogen and glucose-6-phosphate in muscle
- clinical signs: exercise intolerance, muscle stiffness, back pain, shifting lameness, gait changes, muscle atrophy, camped out stance, colic signs
- prevention: feed minimum of 1.5% BW as forage, remove concentrates containing grain and molasses, use alternative energy sources, implement daily exercise regimen
