1
Q
Typical DM intake?
A
1.5-2%
2
Q
What happens to DM when energy requirements are increased?
A
Increase
3
Q
How is dry matter calculated?
A
total weight - moisture
4
Q
What is dietary energy?
A
driving force behind homeostasis
5
Q
How can energy be provided in the diet?
A
- CHO
- complex vs. simple - fats
- oils - protein
- water, mineral, vitamins
6
Q
Define 1 calorie (R)
A
heat required to raise the temperature of 1kg of water by 1 degree celsius
7
Q
how many cals in 1 kcal?
A
1000
8
Q
how many kcals in Mcals?
A
1000
9
Q
how many joules in 1 cal?
A
4.184
10
Q
how many kjoules in kcal?
A
4.184 kjoule
11
Q
Explain what energy partitioning is
A
- energy losses from ingestion to excretion
- greater heat of fermentation in horses
- loss of C and O –> losing energy
12
Q
Define digestible energy
A
energy intake - energy in feces/energy intake x 100
13
Q
Net energy for maintenance
A
Basal metabolism
- minimum energy energy required to sustain life
- brain, tissue functioning, digestion (normal bodily functions)
Voluntary activity
- voluntary, conscious movement
- walking, foraging
Thermoregulation
- energy to maintain body temperature
- E.g. below LCT –> increase energy consumption = require more energy to maintain body heat
14
Q
Net energy for production
A
- hair
- amount of energy dedicated to hair growth (difficult to quantify) - growth, reproduction, milk
- lactation, growing fetus
- foal = part of mares energy requirement (why peak lactation is so energy demanding) - activity
- fattening
15
Q
What is the major source of dietary energy in horses?
A
CHO and fibre and lipid (present in forages)
- CHO make up the single largest component of the equine diet
- sugars/starches are readily digested by the horses, rapidly fermented if they reach cecum/colon
- fiber is poorly digested and slowly fermented in colon
16
Q
Define energy balance
A
energy ingested - energy expended
17
Q
Why is predicting energy requirements so challenging?
A
Drastic changes in energy requirements
- age
- reproductive status
- body condition (fatter = less energy per kg)
- activity level
- breed –> physiologic, metabolic, temperament differences (genetics)
- temperament (cribbing, pacing costly)
- health status (immune response is costly)
- environmental conditions (hot/col = increased energy)
18
Q
Energy requirements/day for minimum working horse
A
30.3 kcal/kg BW
19
Q
Energy requirements/day for average working horse
A
33.3 kcal/kg BW
20
Q
Energy requirements/day for elevated working horse
A
36.3 kcal/kg BW
21
Q
Calculating DE requirement in an average working horse
A
33.3kcal/kg x 450kg = 14,985
22
Q
Energy requirements for peak lactation are comparable to?
A
an endurance horse
= ~175% DE
23
Q
Where do most CHO originate from?
A
plants
- exception: glycogen (animal based)
24
Q
What are monosaccharides? (R)
A
Hexose
- 6 C sugar = glucose, galactose, fructose
25
What are disaccharides? (R)
2 hexoses
| - vast majority of what we see in horse's diets = sucrose, lactose, maltose
26
What are polysaccharides? (R)
Homo-polysaccharides = one repeating unit
- starch (amylose and amylopectin)
- cellulose (similar chains of glucose)
Hetero-polysaccharides
- hemicellulose
- pectin
27
Describe the process of starch digestion
- starts in the mouth --> salivary amylase
- pH of stomach contents variable (more neutral than other species)
- microbial fermentation and breakdown of some starch in stomach
- alpha-amylase in SI (secreted by pancreas)
- maltase and isomaltase (from small intestinal brush border) --> involves sodium dependent glucose transporter (SGLT1) --> circulation
28
How can the bioavailability of different carbs be assessed?
appearance of glucose in peripheral blood (GI)
| - enzymes help to improve starch digestion in horses (increased levels of glucose in blood)
29
Are there limits to small intestinal starch digestion?
- total tract starch digestion = >90%
- site of starch digestion can differ depending on starch intake, starch source, processing method (more eaten --> more to colon)
- activity of amylase in pancreas and small intestine digest low relative to other monogastrics (and highly variable)
30
Energy sources in concentrates
1. Corn
- 25% amylose, 75% amylopectin
- highly digestible in horses
- little starchy CHO reaches cecum (very little bypasses SI)
- unless over consumption
2. Oats
- universally used
- highest protein content and quality of any cereal grain
- ideal for working horses
- can meet energy requirements, palatable, high fibre content --> reduces chance of colic
3. Wheat
- uncommon in horses
- equal of corn (similar in energy, higher in protein; lower in EFA)
4. Barley
- widely available in NA
- beer
- lower in energy content (lower in starch, higher in B-glucan = soluble fermentable fiber) --> reduce glucose levels
31
Affect of bran on horses
By-prouct of wheat milling
- very fibrous and palatable
- high water holding capacity
- very high in P
- -> nutritional secondary hyperparathyroidism
- effects calcium absorption, mobilization of calcium from bone
Big head syndrome, millers disease = swelling of hear in horses working at the mill
32
What's so good about molasses?
By-product of the sugar refining industry --> molasses
- 15-25% water
- 45% sugar
- highly palatable
- good energy source
- good as a binder; reduce dust, bring things together
- never use in large quantities (
33
Describe the process of fermentation of starch in LI
Starch (microbial enzymes) --> glucose (fermentation) --> VFA or excretion of bacterial protein
Oats help prevent rapid fermentation = rapid change in gut bacteria = rapid change in pH
- wheat & barley fermentation rapidly
34
What are the effects of starch reaching the hindgut?
1. decreased energy efficiency
2. increased fermentation
- alter VFA rations
- decreased pH --> acidosis, diarrhea, colic, founder
3. increase protein requirement of microbes and potentially increase microbial protein excretion
4. decrease giber digestion
- fiber digesting bacteria are not as functional at low pH
35
Describe the process of fermentation of fiber in LI
fiber (microbial enzymes) --> mono-saccharides (fermentation) --> VFA or excretion of bacterial protein
- acetic acid
- propionic acid
- butyric acid
36
What are VFAs used for?
Rapidly absorbed with water and Na (remember that glucose also transports with glucose)
- can account for
37
What is the effect of fiber of digestibility?
Increasing fibre decreases digestibility
- fibre --> butyrate --> stimulates cell growth
- binds to everything in GIT producing viscous material
38
Effect of maturity on hay digestibility
Early cut hay and lush green pasture have more digestible fibre and starch than mature hay/pasture
- CHO become more complex with age (digestible CHO replaced with cellulose/hemicellulose)
- throughout season --> simple starch --> complex (hemicellulose)
- lower solubility, increased rate of passage
39
Legumes compared to grass forages
Superior sources of energy, protein and some minerals
- but they are bloat producing because of a high concentration of soluble protein
- more soluble protein = more starch
40
Effects of yeast supplementation
- no effect on protein and DM BUT increased CHO digestibility
- increased fibre digestibility
- increased microbial activity in cecum and colon
41
Is feeding silage a good thing?
Silage has lower pH, higher concentrations of lactic and acetic acid and lower amounts of water soluble CHO than hay
- DM digestibility, blood insulin levels and blood glucose levels were higher in silage fed horses --> improved digestibility/fermentation
- therefore, carbohydrate availability to trained horses from fibrous feed ingredients can be increased through feeding silage
42
What are the main energy substrates provided in grain fed situations?
starch (amylose, amylopectin) and glucose (simple sugars, mono)
43
What are the main energy substrates provided in hay fed situations?
VFAs
44
Increased starch to the cecum/colon leads to an increase in which VFA?
Propionate
45
What is the biggest concern regarding energy balance in a majority of adult horses?
Positive energy balance = exceeding energy requirements --> obesity and decrease reproductive efficiency
46
When might energy requirements be increased?
rapid growth, training, high performance - difficult to be met with hay alone
47
What areas should be palpated to ensure adequate BCS?
- along the neck
- along the withers
- crease down back
- tail head
- ribs
- behind the shoulders
48
Body condition scoring
```
1 = poor
5 = moderate
9 = extremely fat
```
49
Determining kg body weight
[heart girth (cm) x heart girth (cm) x length (cm)]
50
What are the effects of hay and pasture maturity on digestibility?
Early cut hay and lush green pasture have more digestible fibre and starch compared to mature hays and pastures. Since digestible carbohydrates are being replaced with hemicellulose and cellulose as a plant matures, digestibility decreases.
However, because solubility decreases, the rate of passage increases; this can be beneficial in some cases (for example, a horse prone to colic).
51
What is the effect of yeast supplementation on nutrient digestibility?
Yeast supplementation only appears to be beneficial in terms of carbohydrate and fibre digestion. Improved digestion is due to increased microbial activity in the cecum and colon, and therefore, increased fermentation.
52
What is the difference in energy substrates provided in a grain-fed vs. hay-fed situation? When should grain be considered?
Grain = starch (amylose, amylopectin) and glucose (simple sugar; monosaccharides) and hay = volatile fatty acids (acetic acid, propionic acid, butyric acid).
If energy requirements exceed what can be provided by hay alone, then a grain source should be considered for additional energy (quick source). It is important to note that energy from digestion of fibre provides a more constant energy supply compared to the absorption of glucose (this could be of potential importance in endurance exercise and longevity).
Additionally, over supplementation of grain can negatively influence hind-gut fermentation if small intestinal starch digestion is incomplete (can lead to serious health issues, such as colic).
53
What happens when starch reaches the colon?
It decreases energy efficiency, increases propionate (which decreases pH), decreases fibre digestibility and increases microbial excretion.
54
True of False: Wheat has the highest protein content and quality of all cereal grains.
False (oats does)
Equine Final
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