1.2 Comparative Nutrition - Nutrient review Flashcards
Essential nutrient
- Nutrient cannot by synthesized by metabolism
- Must be provided in the diet
Conditionally essential nutrient
- Nutrient can be synthesized from suitable precursor, but not enough during some physiological stages
- Semi-essential: nutrient can be synthesized, but only from an essential precursor in the diet
Nonessential nutrient
Nutrient can be synthesized in sufficient quantities
6 categories of nutrients
- water
- aa (protein)
- cho
- fats and oils
- minerals
- vitamins
What is quantitatively the most important nutrient?
Water
What can water be a source of?
Nutrients
- Na, Ca, trace minerals, others
How are water requirements described?
“Sufficient quantities of water of adequate quality”
What are 2 reasons why water can be a major source of problems?
- Microbiological contamination
- Biofilms
- Groundwater contamination - Chemical contamination
- Nutrients - Na, Ca, phosphates etc. in high quantity
- Toxic compounds
- pH
- Oxidation/reduction potential
How much water do chickens normally consume? What do requirements depend on?
- Water normally ~2x feed intake
- Req depends on: environment (temp and humidity), health, stress
*water intake decrease usually precedes feed intake decrease in sickness
What does water consumption of a pig depend on?
- Body weight and feed intake
- Physiological stage
What are the 4 conditionally essential AA?
- Arginine
- essential for piglets and birds - Histidine
- essential for pregnant sows - Proline
- may be essential for piglets and for chickens fed purified diets - Glutamate
- may be limiting for weanling pig, chick growth
What are the 2 semi-essential AA?
- Tyrosine
- can be supplied from excess Phe - Cysteine
- can be supplied from excess Met
Do animals have a protein requirement?
NO! They require essential AA
- Diet must also contain sufficient amino nitrogen to allow synthesis of non-essential AA by the animal; this is why we consider crude protein level when formulating diets
- Commercial nutritionists have moved away from the concept of formulating to a protein “requirement”
Nutritional valuation of CHOs for pigs and chickens
- Consider starch and fibre separately
- Starch (generally) more available than fibre to monogastrics - Understanding is more advanced for pigs than in chickens
- greater hindgut fermentation in pigs - Starch and fibre influence gut health
- microbiome
- microbially-synthesized nutrients - Enzymatic digestion
- starch and sugars (lactose, sucrose, maltose)
- not all starch is digested (resistant starch) and can behave like fibre (hindgut fermentation) - Not enzymatically digested but fermented:
- Non-starch polysaccharides
- Cellulose, hemicellulose, pectin, fructans
- Oligosaccharides
What CHOs get fermented?
Fibre and resistant starch
- Yields VFA (acetate, propionate, butyrate) absorbed in the hindgut and metabolized for energy
- Energy loss during fermentation (pigs)
- Energy utilization of VFA (pigs is 15% lower than ME from glucose
What are non-starch polysaccharides?
Technically, any polysaccharide that is not starch
- cellulose hemicellulose, pectins, xylans, glucans
- In common usage, “NSP” is usually in the context of SOLUBLE non-starch polysaccharides, typically: arabinoxylans and beta-glucans
What do soluble NSP do?
Increase digesta viscosity
- Reduce mixing of digesta = reduced expose to enzymes = reduced movement of nutrients to absorptive surfaces
- Create a more anaerobic environment = microbial proliferation = many pathogens are anaerobes = immune activation
How are soluble NSP dealt with?
NSP-degrading enzymes
- major effect in decreasing viscosity
- minor effect is the release of sugar molecules for absorption
Utilization of NSP
Energy utilization 0-79% in pigs
- fermentability differs among types of NSP
- affected by feeding level, physiological stage
- lower in poultry
Does not include effects of NSP on digestibility of other nutrients
Feed (exogenous) enzymes can increase utilization
- xylanase to digest arabinoxylans
- B-glucanase to digest B-glucans
What are 2 essential fatty acids? What is a conditionally essential fatty acid?
Linoleic acid and Linolenic acid
Arachidonic acid - derived from linoleic acid
7 macrominerals and 8 trace minerals
Macrominerals
- Ca, P, Na, K, Cl, Mg, and S
Trace minerals
- Fe, Zn, Mn, Cu, Co, Cr, I, and Se
Macro-mineral supply
In grain-based diets
- Ca, Na, Cl: insufficient amounts; addition to diet as limestone
- Phosphorus: problem is it is stored in phytate leading to inadequate available (or digestible) P; addition of mono/di-calcium phosphate, rock phosphate, bone meal or phytase
- K, Mg, S: sufficient contents
What 4 things can phytic acid bind and thereby, reduce the availability of?
- Phosphorus
- Protein
- Starch
- Divalent cations
- Ca, Mg, Zn, Cu, Fe
Phytase
Breaks down phytate molecule
- present to some degree in plants
- endogenous phytase (made by the animal) is low; higher in chicken intestine than pig intestine
- exogenous phytase (added to feed) is produced by microorganisms (yeast and bacteria)
- increased digestibility of minerals: P, Ca, Zn, Na, etc.
- increased digestibility of AA, starch and energy
What are good sources for Fe, Mn, Cu, Zn (trace minerals)?
- sulfates, chlorides
- chelated (“organic”): complex with AA or protein; increased availability bc it is protected from binding by phytate
What are poor availability sources for trace minerals?
Oxides and carbones
How is Se (trace mineral) added to a diet?
Na-selenate, Na-selenite, organic selenium
How are trace minerals usually added to a diet?
Provided in a premix
How are fat-soluble vitamins included in a diet since they are usually low in grain-based diets?
Provided in premix at ~10x requirement or more
- Vit A and carotenoids
- Vit D is added as: feed-grade D3 or vit D metabolites (25-OH vit D3 most important)
- Vit E: a-tocopheryl acetate (synthetic)
- Vit K: included in premixes as menadione (synthetic)
Why is vit C not required by pigs or poultry?
Unlike humans, they can synthesize their own
Water-soluble vitamins
- biotin
- choline
- folate
- niacin
- pantothenic acid
- riboflavin
- thiamin
- pyridoxine
- cobalamin
How are water-soluble vitamins included in a diet?
- provided in premix
- different mixes for growing pigs and sows
- different mixes for layers, broilers, breeders, turkeys - choline, thiamin, B6 in grain-based diets
- sufficient for growing pigs, but not sows
- usually supplemented for poultry - Other water-soluble vitamins
- marginal contents for growing pigs, inadequate contents for sows, supplemented
- supplements in poultry
5 important notes about energy
- A property, not a nutrient
- Derived from nutrients:
- protein, lipids, CHOs
- VFA (from hindgut digestion) - Energy yield differs btw nutrients
- No energy from minerals or water
- Most expensive feed component
- proportional increase in energy costs more than a similar proportional increase in any other nutrient
Limiting nutrient is a concept that relates…
Performance to nutrient supply
- asking if the diet has enough of a particular nutrient to support the desired performance
First limiting nutrient
Nutrient present at the lowest amount relative to the requirement
- amount of this nutrient will determine the level of production, regardless of other nutrients that might be deficient
- can apply to any req nutrient; most commonly individual AA
First limiting vs second limiting nutrient
First limiting
- most deficient relative to requirement
Second limiting
- still deficient relative to requirement
- not relevant until the first limiting nutrient has been addressed
Commonly limiting nutrients
- AA
- Lys usually 1st limiting for pigs
- Met usually 1sst limiting for chickens
- Possibly limiting: threonine, tryptophan - Energy (limit to intake)
- For chickens, pigs with high growth potential - Vitamins and minerals
- Supplemented to diets to avoid them from being limiting
Limiting AA
- When the supply of one essential AA is insufficient, protein synthesis is reduces
- Which AA is limiting is specific to a feedstuff
- Different feedstuffs may have different limiting AA
In cereal grains (barley, wheat, corn), what is the first limiting AA?
Lysine
- Threonine or typtophan is second limiting in many feedstuffs
High protein diets vs. low protein diets in terms of limiting AA
High protein diets more likely to provide sufficient amounts of a greater number of essential AA
Low protein diets
- reduce N excretion, pollution
- becomes more important to balance for a greater number of essential AA
