4b Nutrient Requirements of Horses 1 Flashcards
What is the definition of a mature horse?
- considered mature at 86% of body weight (36 months)
- dependent on breed/use (2-6)
What are 4 factors that influence the energy requirements of horses?
- Breed
- Age
- Reproduction
- Activity level
Define maintenance energy requirement (MER)
- amount of dietary energy needed to prevent change in total energy contained in the body of a horse
- does not include energy needed to support additional activity (gestation, lactation, growth, performance)
How is MER established in mature horses?
- metabolic body weight (surface area vs body weight)
Explain the need for metabolic body weight.
- not all tissues require energy to be maintained
- MBW ensures that these tissues are not accounted for
Which 3 parts of daily heat production form together the heat increment?
- heat of product formation
- heat of digestion and absorption
- heat of waste formation and excretion
- heat of fermentation
Why does gut size matter in heat production?
- in animals that ferment a lot of feed, cells proliferate much more and gut is bigger and heavier
How can body condition score affect requirements?
- low muscle tissue = low energy requirement
What is the average DEm of horses?
30.3kcal/kg BW/day
Do you think the minimum maintenance requirement calculated is high, low or correct?
- low because animals were confined
What were the calculated average and elevated energy requirements?
- average 10% increase
- elevated 20% increase
What are the 5 climatic variables that have effects on energy?
- ambient temperature
- wind velocity
- global solar radiation
- precipitation
- relative humidity
(horses must maintain constant core body temperature)
What effects can extreme cold cause?
- increased eating
- increased hair coat
- decreased rectal temperature
- decreased respiratory rate
What effects can extreme heat cause?
- increased sweating rate
- increased respiratory rate
- decreased feel intake
- increased water intake
What is a thermoneutral zone?
- when metabolic heat production does not need to increase to maintain thermostability
What is the general lower and upper critical temperature?
- 15C
+ 35C
How much should DE intake increase for each degree below LCT?
2.5%
How can feed management help animals cope with hot or cold temperatures?
feeding a more forage based diet in winter increases fermentation which helps them maintain heat
What is the total body water in adult horses?
- 62-68%
- water balance achieved if water loss = water intake
How long can water restriction be tolerated?
- extended periods but more so tolerated with lack of feed as well
What are the 4 main types of water loss?
- fecal losses (3-3.8L/100kg)
- urinary losses (0.5L/100kg)
- respiratory losses (0.8-2.1L)
- cutaneous losses (1.7-3.3L/100kg)
Why is there more water loss with hay diets
- hay higher in soluble fibre so more water in poop
What are the 3 main types of water intake?
- drinking (5-9.6L/100kg)
- food (hay less moisture than pasture)
- metabolic water (0.68L/100kg)
What is the main determinant of total water intake?
- body weight
What is the only amino acid requirement that has been established in horses?
lysine
Why can you feed ruminants non protein nitrogen but not horses?
- horse cannot absorb amino acids after small intestine
Protein digestibility is correlated to ______
dietary CP content
How do you calculate the lysine requirement?
lysine (g/d) = CP requirement x 4/3%
What is an ideal protein?
- 100% biological value
- ability for a specific dietary protein to supply amino acids in the relative amounts required for protein synthesis by body tissues
How can the ideal protein be estimated in horses?
- by using muscle tissue
- use these ratios to estimate requirements for EAA
What are the effects of protein deficiency?
- weight loss in adult horses
- fetal loss in pregnant mares
- decrease milk production in lactating mares
- loss of muscle in exercising horses
What are the effects of protein excess?
- increases urea which is excreted in urine
- increases water loss
- increases water requirements
- decrease growth in younger horses
- increases Ca and P loss in weanling horses
What are some examples of carb containing feeds?
- forage
- concentrates
- grain by products
Do all carbs contain the same amount of gross energy?
- yes, but different digestible, metabolizable and net energies
What fractions are currently used?
- NDF neutral detergent fibre (cellulose, hemi cellulose nd lignin)
- NFC non-fibre carbohydrates (mono, di, oligosaccharides and starch)
What is the new proposed system of fractions?
- hydrolyzable CHO
- rapidly fermented
- slowly fermented
Cecal VFA production can meet up to what percentage of MER?
- 30%
What are fats used for in the diet?
- improve energetic efficiency
- enhance body condition
- diminish excitability
- help increase fat oxidation
- facilitate absorption of ADEK vitamins
What are the 2 essential fatty acids and what are their requirements?
- linoleic acid
- alpha-linolenic acid
- no requirements
Do added fats have increased or decreased fat digestibility?
- increased
What is calcium important for and what is the requirement?
- 04g Ca/kg BW per day
- muscle contraction, cell membranes, enzymes, blood homeostasis
What is phosphorous important for and what is the requirement?
- 28g/kg BW per day
- important for energy reactions and synthesis of nucleic acids
What is the Ca:P ratio?
~1.4:1
What are potassium and sodium requirements, and how are they met?
25g K/day 10g Na/day
- salt block and forages
What are the 3 main vitamin requirements?
A D E
