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Feed intake regulation
The interrelated mechanisms that attempt to regulate energy intake, in relation to energy expenditures
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Hunger
The complex of sensations which compels an animal to obtain food
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Satiety
The complex of sensations which compels an animal to stop eating
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Palatability
The degree of readiness with which a particular feed is selected and eaten
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Factors affecting feed intake
- Species: breed
- Sex: extrus
- Environment: space, stocking density, nutritional factors, physiological state
- Palatibility
- Age
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Palatability affected by
- Taste (bitter, sour, salty, sweet, umami, kokumi)
- -tastebuds, greatest to least: chicken, dog, human, sheep & goat, cattle
- odour
- sight (orientation and texture)
- texture (particle size)
- novelty
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Summary feed intake
- Generally, animals eat to meet their energy requirements
- Changing circumstances energy output increases, energy input changes
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Short-term control of feed intake (hours)
- Neural receptors and afferent neutrons
- -GI tract, liver, other organs
- Gastric distencion/contraction
- Humoral factors - hormones & metabolites
- Glucostatic theory (intake controled by blood glucose)
- Aminostatic control
- -monogastrics crave specific amino acids
- Thermostatic control
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Long-term control of feed intake
- Animals seldom starve or overeat
- Hibernating animals
- Combination of signals that contribute to long-term control of feed intake
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Lipostatic control
Animals eat to maintain set lipid reserves
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Seasonal affects
Regulated in part by the pineal gland
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Current understanding
- Multiple control mechanisms working together
- CNS recieves, integrates information
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Gastrointestinal receptors
- Chemical:
- -receptor in gut for fat & protein
- -receptors for blood glucose
- Osmotic pressure
- Stretch receptors
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Hormone controls
- Cholecystokinin
- -released in resonse to fat & protein in the small intestine
- -hunger suppressant
- Insulin
- -reduces food intake-anorexia
- -uptake of glucose by cells
- -reduced insulin sensitivity ->obesity and diabetics
- Leptin
- -most important hormone regulating energy balance
- -feedback regulation
- Ghrelin
- -increases foo intake
- -released by the stomache
- -counterpart to leptin
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Physiological responses that affect feed intake
- Growth hormone
- Stress hormone
- Reproductive hormone
- Opioids
- Immune hormone
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CNS control of feed intake
- Control of feed intake is ultimately under the control of the brain.
- Hypothalamus
- Ventromedial nucleus (satiety centre)
- Lateral nucleus (hunger centre)
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In most production situations
- High feed intake is necessary
- Efficiency of production generally realtes to energy intake
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FCR
- Feed Conversion Rate
- g feed/g gain
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Residual feed intake
- Acurate feed intake - expected feed intake
- Expected feed intake is based on calculated requirements
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Restrict feed intake:
Broiler breeders, sows, compensatory growth
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