nutritional management of performance horses Flashcards
nutritional considerations for performance horses
meet nutrient requirements, maintain normal GI tract, manage body weight, address limiting factors
how to determine nutritional requirements
requirements vary with frequency, duration and intensity of activity (often measured by Heart Rate), heart rate goes up in response to how much O2 the body needs
what affects exercise intensity?
speed, weight carried/pulled, incline, ground resistance, coordination, stride length, athletic ability etc
activity definition
duration, intensity, frequency
nutrient requirements of performance horses
maintenance+exercise+other
maintenance=requirements of the same size, idle, nonbreeding horse
3 levels of maintenance
minimum, average and elevated
most performance horses have average maintenance values and some may have elevated maintenance values
exercise requirements definition
the nutrients needed to support exercise above maintenance, exercise intensity, duration and frequency varies
other requirements for performance horses
nutrients needed to support other activities associated with a performance horse’s “lifestyle” ex. transportation to and from events
NRC definition of light work
1-3 hr, walk and trot
moderate work
3-5 hr walk trot canter easy skills
heavy work
4-5 hr walk trot canter gallop, hard skills
very heavy work
advanced race training, elite 3 day
how does exercise affect calorie requirements?
calories needed increase with the level of work
how does exercise affect protein requirements?
protein is used at a very low rate for ATP synthesis for muscle contraction, but increased tissue turnover and lean body mass may increase with training so protein needs (grams/day) of athletes are elevated, protein quality (especially essential AA) is impK reortant
how does exercise affect Ca and P requirements?
exercise may increase bone turnover, with training bone density may increase so Ca and P requirements are elevated compared to idle horses
how does exercise affect Na, Cl and K requirements?
exercise increases the electrolyte requirements due to sweating
composition of sweat
2.5-3 g Na/L
1.2-1.5 g K/L
5.0-5.5 g Cl/L
amount of sweat=0.25 to 2 L/100 kg BW
how are sweat losses estimated in NRC table?
estimated on a non-excessively hot or cold environment
how does exercise affect vitamin and mineral requirements?
some vitamins and minerals are used in energy metabolism for O2 transport etc. examples are P, Mg, Cu, Fe, thiamine, B12, folic acid, riboflavin, pantothenic acid
requirements for these nutrients may be increased by exercise but not much info on the size of the increase
Vitamin E, selenium, zinc, Vit A and Vit C help protect the cell from damage during exercise and help repair cells damaged during exercise, requirements for these nutrients may be increased by exercise but not much info on size of increase
Comparing nutrient requirements between nutrients
not all nutrients change proportionately, exercising horses usually need diets that are different than other classes of horses but not all exercising horses are the same
sources of calories in a horse’s diet
fiber- 1.6-2.4 Mcal/kg DM, from forages, pulps, brans and cereal byproducts
starch-3.5-4 Mcal/kg DM, from cereal grains and grain byproducts
fat-8.8-9.2 Mcal/kg DM, from vegetable oil, seeds, some seed meals, some brans and cereal grains, can feed up to about 10% of concentrate in fat before palatibility is a problem
risk factors of gastric ulcers
long intervals between meals, reduced chewing/forage, reduced fiber mat, VFA production by fermentation of starch in the stomach-ALL ASSOCIATED WITH LOW FORAGE INTAKE
gastric ulcers may cause-decreased performance and decreased feed intake
problems of starch bypass to the LI
increased acid production in LI causes reduced pH, disrupted microbial community, reduces fiber digesters, decreased feed intake and starch digested in the LI yields fewer usable calories for the horse
% of starch digested in the small intestine
Oat starch is more easily digested in the small intestine than corn starch, grinding increased the digestibility of both oat and corn starch
% of starch that by-passes to the large intestine
corn starch is more likely to reach the LI than oat starch, starch in whole grain is more likely to reach the LI than starch in ground grain, unprocessed corn is most likely to cause LI upset
effect of meal size on % of starch reaching the LI
less starch to the LI when smaller meals are fed
alternatives/modifications to reduce starch
may replace some starch with fat-fat contains more than 2x DE as starch per gram, reduce cereal grains in mix and increase vegetable oil
relpace grains with highly digestible fiber in concentrates (beet pulp/soy hulls)-beet pulp has 90% DE of oats, replace some cereal grains with fiber andf fat, get similar DE content as in traditional mix, but less starch
use starch sources that are well digested in the SI
change meal size-starch in small meals is digested better in SI than starch in large meals
reduce concentrate by using best forage possible-more palatable to encourage intake and more calories per kg
what limits performance?
depends on event and individual, in general strength, stamina and fatigue are limiting factors.
some components like substrate availability, end product accumulation and oxygen availability are also limiting
oxidative (aerobic) metabolism
carbohydrate and fat»>ATP, CO2 and water, most efficient, occurs in type I and type IIA
glycolitic (anaerobic) metabolism
carbohydrate»>ATP and Lactic acid, less efficient (less ATP per unit carb) but faster, type IIA and type IIX
Muscle fiber types
type I, type IIA and type IIX
type of muscle influences strength, speed and endurance, characteristics can change with training, fibers become more oxidative (rely more on O2) and generate less lactate at a specific work load
energy sources based on exercise intensity
low intensity exercise-mostly fat and some carbohydrate
sprinting/short burst strength-mostly carbohydrate, some fat
protein as an energy source
protein contributes less than 5% of calories used during exercise unless fat or other carbohydrate is not available
fat as an energy source
fat used during exercise comes mostly from body stores and supplies are not usually limiting
carbohydrate as an energy source
comes from muscle glycogen (polysaccharide of glucose, starch) or blood glucose from the liver or food
carb stores vs fat stores
carb stores are much smaller than fat stores, carb availability can limit some types of athletes
when are carbohydrate stores limiting?
low muscle glycogen stores will impair performance-during endurance exercise glycogen stores may be depleted and play a role in fatigue, stores must be full at start, feeding at rest stops provides carbs
low muscle glycogen will impair performance-for best performance, muscle glycogen must be restored between events, poor appetite after events may delay glycogen restoration
dietary management of carbohydrate stores
diet should contain some starch or glucose producing compounds-encourages glycogen repletion, feeding close to end on competition may help
train the muscle to use fat and spare carbs-feeding additional fat in the diet may do this but probably takes weeks to adapt
provide carbs at rest stops for endurance horses
what energy sources limit performance?
during racing, starting with low glycogen stores may affect performance, but if stores are full at start glycogen depletion does not occur during a race (carbs are used but duration is short)
nutritional management of intramuscular acidosis
enhance intramuscular buffering-type IIX muscles have higher buffering capability than type I fibers, but no known way to increase buffering yet
enhance blood buffering-feeding baking soda may increase blood buffering, but is illegal in most competition
reduce acid producing ingredients-avoid excess protein (horses with too much protein tend to have lower blood pH), ensure electrolyte balance (Na, K, Ca vs S, Cl)
pre-competition feeding of concentrates
increases blood glucose-increases insulin
insulin may decrease the ability of the body to mobilize fat for energy (this could increase the use of carbs and thus accelerate the depletion of glycogen)
general recommendation for strenuous events is to not feed concentrate 3-5 hours before the event/race unless you start right away (before insulin increases)
pre-competition feeding of forage
each kg of fiber in LI holds 1-2 kg water
reduce hay intake 12-24 hrs prerace to reduce GI weight
reduce hay from 7 kg to 3 kg to reduce total BW by 7-8 kg
for horses that run and jump weight reduction may be important
weight to power ratio
a lighter body puts less concussion on the skeleton, a lighter body is easier to move
how much water is consumed per lb of DM?
2-3.5 lb of water per lb of DM
the more DM consumed means more water is consumed
where is most of the weight of the digesta
in the large intestine, each lb of DM in the large intestine is accompanied by 2-3 lb of water, the LI has 25-45 lb of ingesta under usual circumstances, higher fiber diets mean the horse carries more undigested feed material and water in the LI
how to reduce LI contents
reduce feed intake 12-24 hrs pre-competition by 50%
this reduces LI content by 25-50%=body weight reduction of 6-22 lbs (reduction in gut fill)
furosemide (lasix)
`diuretic that induces weight loss of 2-3% in about 4 hrs of administration, a 1000 lb horse will lose 20-30 lb of water
managing BW and condition
ideal weight and condition vary by activity and individual. excess weight may be detrimental to horses that run and jump, too little weight may reduce strength
how to maintain ideal body condition
energy balance-calorie intake is the most important nutrient affecting body condition
positive energy balance
body condition increases, calorie intake is greater than the horse uses
negative energy balance
body condition decreases, underfeeding 3 Mcal/DE per day is about 90 Mcal/DE per month so about 10-15 kg will be lost
meeting DE needs in elite athletes
need high DM intakes and high concentrate intakes, causes risk of GI disturbance
in negative energy balance you probably loose fat and muscle
heat accumulation
heat is an end product of exercise, some heat accumulation can be good-“warm up” that enhances blood flow, optimizes metabolic rxns and enhances oxygen delivery to muscles
but excess heat accumulation can cause muscle damage, GI damage and CNS impairment
mechanisms of heat dissipation
convection, conduction and radiation (all work best in cool climates)
evaporation is most important in hot weather, most effective when humidity is low and primarily occurs in sweating
sweat composition
fluid and electrolytes, fluid comes from plasma, if plasma volume decreases too much, total blood volume rapidly decreases, meaning there is a decrease in blood pressure, sweating requires blood flow to the skin
fluid depletion (dehydration)
mostly an issue in warm/hot environments, endurance/3 day horses lose fluid at about 3.5% BW even with water available at rest stops, if you restrict hay and water before competing there will be an increased chance for dehydration
affects of heat accumulation and fluid depletion
reduce blood flow to muscles by competitions for blood flow between skin and muscle and by reduced plasma (and blood) volume
lower delivery of oxygen to muscles increases anaerobic metabolism and higher lactate accumulation
may also affect blood flow to GI tract, muscle function and integrity and affect the brain
feeding nutritional strategies to reduce heat accumulation
maximize hydration pre-event
water intake before event, feed diets high in water-holding capacity to enhance water reservoir in GI tract, high fiber diets are favored over low fiber or hay restriction, but this will increase weight carriage
feeding and nutritional strategies during event to reduce heat accumulation
maximize water intake during the event, accustom horses to drinking during training, judicious use of electrolyte supplements may be helpful during the event
how is thirst stimulated?
by increase in electrolyte concentrations in plasma, but with high electrolyte losses in sweat of horses, plasma electrolyte concentrations may not change or may decrease
what limits performance?
depends on event and individual, some components=availability of substrates for ATP synthesis in muscle fibers and end product accumulation (lactic acid and heat), oxygen availability
oxygen availability
depends on cardiovascular factors-competition for blood flow and blood volume (depletion of plasma volume)
depends on respiratory factors-ability of respiratory system to oxygenate blood and remove carbon dioxide
feeding strategies for optimizing respiratory function
minimize inflammation of upper and lower airways, control exposure to dust and mold with hay quality, hay soaking, hay form and hay feeders
