Nutrient Requirements of Horses Presentation Part 2: Energy (Continued) #8895-C

Requirements Many factors affect energy needs: – Individuality of horse – Body makeup – Temperature & humidity of environment

Requirements How much energy is expended influenced by: – How intensely & how long a horse works – Rider ’ s ability & weight – Condition of the surface where horse works

Requirements - Maintenance Energy needed for maintenance Maintenance energy = energy needed to sustain body weight while performing non- work activities Weight used to calculate maintenance energy requirement

Requirements - Maintenance Maintenance DE (Mcal/day) = (W) is horse ’ s weight (600 kg or less)

Requirements - Maintenance Different formula for horses weighing more than 600 kg Larger horses move around less voluntarily Previous formula overestimates energy needs of bigger horses

Requirements - Maintenance Maintenance DE (Mcal/day) = (W) – (W x W)

Requirements - Maintenance Visit National Research Council ’ s publication, “ Nutritional Requirements of the Horse ” to devise a ration Tailor feedings to meet the needs of “ easy keepers ” or “ hard keepers ”

Requirements - Maintenance Easy keepers do not need as much feed as hard keepers do to stay fat Notice if horses get fat or thin – Adjust feed accordingly

Requirements - Maintenance If horses eat too much, they will become obese – Especially if not getting enough exercise If they do not get sufficient energy, horses will: – Lose weight – Lose condition – Become tired easily

Requirements - Reproduction Important mares have good body condition at breeding time Body condition influences rate of conception – Conception - act of becoming pregnant

Requirements - Reproduction If horse is thin but gaining weight at breeding time, they are twice as likely to conceive, than if thin & maintaining In thin horses, estrus cycle may be delayed & irregular May fail to ovulate, conceive, or maintain pregnancy

Requirements - Reproduction Estrus - heat cycle of reproduction Ovulate - to release the egg during the estrus cycle Good or fat condition = high conception rates

Requirements - Reproduction Body condition score determines need for energy in diet Thin mares - energy intake increases 10-15% above nutritional requirement – Helps to put on weight – Exhibit higher condition score

Requirements - Reproduction Too fat - energy intake decreases 10-15% below the nutritional requirement – Helps to lose weight – Have lower condition score

Requirements-Gestation Last three months - fetus develops most & energy requirement increases greatly To get estimate of amount of DE needed, multiply maintenance needs by: – ninth month – tenth month – eleventh month

Requirements-Gestation For example: – 500 kg mare – Tenth month of gestation 16.4 Mcal x 1.13 = 18.5 Mcal/day of DE

Requirements - Lactation Lactating mares produce large amounts of milk in early lactation (weeks 1-12) – 3% of body weight For example: A 500 kg mare generates 15 kg – 33.6 lbs of milk daily

Requirements - Lactation Percentage reduces to 2% of body weight/day in late lactation (13-24 weeks) DE depends on content & amount of milk 792 Kcal of DE are needed to produce 1 kg of milk

Requirements - Growth To calculate energy needs for maintenance & growth use the following formula: Maintenance & Growth DE (Mcal/day) = [Maintenance DE] + [ (X) – 0.023(X x X)][ADG] – ADG - average daily gain – X - horse ’ s age in months

Requirements - Growth If fed too much energy, some may grow way too fast for the increase of their body weight Can influence soundness & life expectancy May develop developmental orthopedic disease (DOD)

Requirements - Growth DOD - various types of bone disorders such as: – Enlargements & deformities of ankles knees, & hocks – Contraction of pastern tendons If ration altered too quickly by adding energy, horse may develop DOD

Requirements - Work Determining DE requirements for work is difficult Many factors cannot be measured Some of these include: – Condition & training of animals – Ability & weight of rider – Composition of diet

Requirements - Work Energy requirements divided into light, medium, & intense work Light Work: – Hunter flat work – Western pleasure

Requirements - Work Medium work: – Ranch work – Roping – Cutting – Barrel racing – Jumping Intense Work: – Racing – Polo

Requirements - Work Energy needs may vary due to: – Type of horse – Type of work – Size of load