14: Nutrient requirements of exercising horses Flashcards
What is required for bone remodeling? Why?
Moderate exercise with rest causes remodeling of long skeleton bones
bone structure changes with rest (most porous)
What are the risks of exercise?
Risk of microfractures and injury if intensity increases too rapidly
Full bone turnover takes approximately 6 months
Slide 6
Look
3 types of fiber in equine muscles? What are they for/do they do
Type 1: Slow-twitch for endurance
- aerobic
- oxidize triglycerides
Type 2A: intermediate fast twitch
- anaerobic + aerobic
- can use both intramuscular glycogen and triglycerides
Type 2X: fast-twitch for sprints
- anaerobic
- fully reliant on glucose, glycogen for E
- low oxidative potential
Kinetics of gas exchange in equine physiology
- maximum rate of O2 uptake/min is double that of human athletes
- splenic reserve of RBC (carry oxygen; releasing them from the splene increases oxygen carrying capacity of horse)
Factors affecting nutrient/energy requirements of hoses during exercise
- Duration
- Intensity (speed, ground resistance, incline)
- other (number and height of jumping efforts, performance of extended and collected gaits, amount of weight carried/pulled)
Energy is required in an exercising horse for…
maintenance + energy for daily exercise effort
May need additional E for transportation, stress, etc
Energy requirement of a horse varies depending on
- the horse
- level of exercise
- type of exercise
- rider weight and experience
- climate
- ground conditions
Categories of exercise in horses
Light, moderate, heavy, very heavy
slide 11
Oxygen utilization is used to measure… What is it related to?
Used to measure energy expenditure
Closely related to heart rate
Linearly related to speed
Slide 12, 13
How does the energy requirement for exercise calculation change in light, moderate, heavy and very heavy work
Light work
DE = (0.0333 x BW) x 1.20
Moderate = 1.40
Heavy = 1.60
correction factor to support exercise
What nutrient is most used in high intensity exercise?
Carbohydrates
Increased intensity = increased CHO use bc of recruitment of fast-twitch muscle fibers
Anaerobic metabolism
Where does the body get glucose (CHO) for exercise
Muscle glycogen, blood glucose, hepatic glycogenolysis, or hepatic gluconeogenesis
What happens when glycogen levels re depleted? Does CHO loading work in horses?
Fatigue resistance reduced (get tired easier)
A little bit, but they are mostly hindgut fermenters and too much starch for too long = metabolic issues
Look at slide 16
Supplementation of _________________ may spare glucose during _______________
Fats and fatty acids for at least 2-3 months
Low and moderate exercise (beta-oxidation)
Important n-3 and n-6 f.a.
Linoleic acid forms arachidonic acid (n-6’s)
a-linolenic acid forms EPA and DHA (n-3’s)
Why might EPA and DHA supplementation be beneficial?
They alter cell membranes of platelets, erythrocytes, neutrophils and monocytes
- Increase fluidity of RBC
- Decrease inflammatory response
Protein use during exercise? Prolonged exercise reduces…
Protein metabolism estimated to be only 5-15% of E expenditure during exercise
Serum concentrations of branched chain AA are reduced (oxidized for E)
Effects of high protein intake on performance
No detrimental effects proven, but no evidence of better performance either
Supplemental protein/aa is required for what during exercise?
For developing and repairing muscle
Lysine requirement formula
= 4.3% x CP requirement
What minerals are important in exercising horses? Why?
Calcium, Phosphorus, and Magnesium
- all required for bone development
- increased requirement met through additional feed for energy (increase intake must be accompanied by exercise for metabolism)
Vitamin requirements in exercising horses
No clear requirements established for working horses (most likely met through increased feed intake)
Thiamin (B1) supplementation may help improve glucose metabolism and prevent lactate accumulation
Water loss during exercise? Requirement depends on? Intake increases how much?
Can account for 3.6-7.7% BW loss during performance
Dependent on conditions (more sweat in hot, humid environments) and duration of exercise
Intake can increase 2- to 3- fold over maintenance requirements
Three disorders associated with exercise
- Gastric ulcers
- Post-exhaustion syndrome
- Polysaccharide storage myopathy (PSSM)
What are gastric ulcers? Symptoms? Prevalence?
Erosion (lesions) of the squamous mucosa due to exposure to gastric acid
Reduced appetite; causes pain after eating
Effects 40-90% of performance horses (increases with increase in activity); up to 100% in racing TBs
Causes of gastric ulcers
- contracted stomach (small)
- continuous HCl secretors
- contraction of abdominal muscles
- high rapidly digestible CHO meals (starch and sugar)
- fasting and amylolytic bacteria
Prevention/treatment of gastric ulcers
Let the horse graze (remove GI stress and exercise)
Get CHOs out of the diet
What is Post-Exhaustion Syndrome? Cause?
Muscle stiffness and reluctance to move that occurs 2-4 days post-exercise
Preface trying up or rhabdomyolysis
Cause is muscular accumulation of lactate, depletion of glycogen (exposure to anaerobic metabolism)
Prevention of post-exhaustion syndrome
- addition of electrolytes to diet
- feeding calcium carbonate
- alter training to increase conditioning (increasing aerobic metabolism)
- allow for adequate slow cool-down after heavy exercise
- if severe administer IV calcium gluconate, magnesium, phosphate ions, vitamin D
What is Polysaccharide storage myopathy? Cause?
Genetic disorder (PSSM1 or PSSM2): difficulty storing glucose as glycogen in muscle tissue
Cause is high concentrations of glycogen and glucose-6-phosphate in muscle
Clinical signs of PSSM
- exercise intolerance
- muscle stiffness/pain
- shifting lameness
- camped-out stance
- colic symptoms
- muscle atrophy
What is PSSM1? PSSM2?
PSSM1
- single base substitution on GYS1
- increase glycogen synthase with inadequate glycogen branching enzyme
- prevalent in draft horses
PSSM2
- no GYS1 mutation
- unknown cause
- Prevalent in quarterhorses, warmbloods
Prevention of PSSM1
- feed minimum of 1.5% BW as forage
- remove concentrates containing grain and molasses
- use alternative energy sources (fat, protein, fiber)
- implement a daily exercise regimen (use glucose in blood so it does not need to be stored as glycogen)
Do what you can to ensure horse does not need to create glycogen
Grazing behaviour in horses
Graze continuously, prefer herds
Graze 10-17 hours/day if on pasture
- usually during day, 20-50% at night
- nocturnal intake depends on season
Horses adjusting to diet energy density
Horses do not adjust food intake to diet energy density
- seasonal pattern of feed intake
- increase weight in spring; reach max weight in summer; progressively lose weight in fall and winter
Voluntary intake affected by…
Palatability
- defined by orosensory sensations
- alfalfa > grass
Highly selective eaters
- select forage on basis of growth rather than species of grass
- meal size and frequency affected by diet
- preference for what is known
Group vs individual feeding in horses
Group feeding affected by social status, variation in appetites, intake rate
Limited feed creates aggressive behaviour
How does environment affect grazing time
- seasonal eating
- rain, wind and high temps decrease grazing
- high humidity increased grazing
- snow cover can influence grazing time
Anorexia in horses
- typically indicative of an illness
- may be caused by dental problems
- can be a learned behaviour (attention)
Coprophagy in horses
- not a normal behaviour in horses
- adult horses will not graze in areas contaminated with equine feces
- exception: foals will consume dam’s feces up to 2 months of age (to establish microflora with moms microbes before start consuming fiber)
Geophagia in horses
Dirt-eating
- not an uncommon behaviour
- may be used to to acquire salt and trace minerals
- sand may create colic or diarrhea
Wood chewing in horses
- undecided if this is a normal behaviour of predecessor to cribbing
- not uncommon in feral horses and TBs
- may cause SI obstruction
- typically caused by inclement weather or lack of fiber in diet (timber is insoluble fiber)
Stereotypic behaviours in horses
Cribbing: incisor teeth grip an object, horse pulls back and gulps air. Associated with drop of stomach pH and incidence of gastric ulcers
Stall-walking: constant movement in circles around an enclosed stall
Weaving: shifting weight from foreleg to foreleg while stationary, usually in confined space
How can stereotypic behaviours be alleviated by feed management
A bit
- providing more forage (more hindgut fermentation = more GOP1 (incretin w calming effect))
- providing fewer concentrate meals per day
