If you are a Cal Poly student enrolled in AVS 303, then these notescover
every subject that will be (possibly) be covered on the final examination.
Do not memorize (you won't be able to), try to understand overall concepts
and relationships as much as possible. Make sure you are familarwith the
calculations we have covered in class, particularly those covered most
recently. These notes are a little cryptic (since I wrote themto lecture
from, not publish), but you should be able to use them to fill in anygaps
in your own class notes (assuming you took any). :-)
If you are NOT enrolled in AVS 303, and are just cruising the websitefor
some obscure reason, you're welcome to do so as well. :-)
Good luck!
LIPIDS
Nutritionally, fats supply a source of energy and essential fatty acids,
required for absorption of fat-soluble vitamins (A, D, E, K)
Proteins 5.65 kcals/g
Carbos supply 4.15 kcals energy/g
Fats provide 9.40 kcal/g, 1.66 - 2.25 times the energy in protein orcarbos,
respectively
Lipid = glycerol backbone with fatty acid chains attached
Fatty acid is a chain containing between 2 to 24 carbons. If allthe C's
are occupied by H molecules, it's saturated. If there is onedouble bond,
it's unsaturated; two or more double bonds = polyunsaturated.
The degree of saturation is going to affect the melting point of theoil and
also how quickly it's going to oxidize. The more saturated afat is, the
more solid it is at room temperature. The more unsaturated, themore liquid
it is.
Also, the more unsaturated it is, the faster it's going to oxidize.
Oxidized fat = rancid => unpalatable => affect fat-soluble vitamins
Fatty acids in animal tissue are almost always going to be straight-chained
and have an even number of carbons. Branch-chained FAs or FAswith odd
numbers of carbons are usually produced by microorganisms, most likelygoing
to be found in body fats of ruminants.
Fatty acid -OOC/\/\/\/\/\CH3 The carboxyl group of eachof three FAs
attach to the glycerol backbone = triacylglycerol (older name triglyceride)
Digestion of fats
Primary site of digestion of fats in mongastric is small intestine
Lipid is emulsified by bile from the liver, lipase cleaves theglycerol
from FA chains, which are then absorbed through the intestinal wall.
In ruminants, microbes in rumen are capable of altering dietary FAs,any
carbon in the chain that is unsaturated will be fully saturated.
Encapsulated fats which bypass the rumen are not saturated. Lipidsabsorbed
in SI.
Maximum tolerance of fat in the diet depend on the species
Horses under clinical conditions can tolerate up to 20% of their dietas fat
(10% more usual)
Dogs up to 40%
Ruminants only 7-8%, because more than that adversely affects microbesand
decreases feed consumption and fiber digestion. Can be fed moreif fed as
bypass fat.
Calves can be fed 20-30% because until 6-8 weeks, essentially a monogastric
species
Essential fatty acids are FAs that the animal cannot synthesize. For
mammalian species, these are linoleic and linolenic (cats also arachidonic).
Linoleic and linolenic are C18:2 omega 6 FAs (can be omega 3, but thoseare
different).
Monogastric species require essential FAs as 1% of the total diet. Symptoms
of deficiency are scaly skin, reduced growth and reproduction, edema,
subcutaneous hemorrhage, poor feathering.
The symptoms do not occur in ruminants even on a fat-purified diet,because
microbes capable of synthesizing all the fats they need.
Deposition of body fat:
Lipids are the only nutrient that the body has an unlimited capacityto
store excess.
Lipids are stored in the form of triacylglycerol/triglyceride
The form of dietary fat for the most part does not affect body fat
composition in ruminants, because microbes saturate everything, sobody fat
is primarily saturated. Can be manipulated somewhat if you feedbypass
fats, but not a whole lot.
Dietary fat composition will affect body fat composition in monogastric
species. Animals, particularly poultry and swine, fed primarilyunsaturated
fats will have higher degree of unsaturated FAs in body fat. This affects
the characteristics because unsat are softer, have lower melting point,
which affects processing and carcass quality. Animals fed primarilysat
fats are going to have harder fat.
Carcass can also be flavored by fats, ie fish oils.
MINERALS
Minerals are inorganic substances, cannot be synthesized, decomposedoutside
of a supernova.
Classified according to concentrations found in animal body:
More than 100 ppm are macrominerals: Ca, P, Cl, Mg, K, Na and S
Microminerals (trace minerals) are less than 100 ppm: Cr, Co, Cu, F,Fe, I,
Mn, Mo, Ni, Se, Si and Zn. Possible future addition may be B.
All minerals are essential - amounts req'd are different, but all are
required.
Minerals represent about 3.5% of the total body composition, of which46% is
Ca and 29% is P.
K, S, Na, Cl and Mg = 24%, rest = 0.3%. 99% of the calcium isstored in
bones and teeth., 80% of P.
Minerals are absorbed primarily in the small intestine in their ionicform,
absorbed either actively (Ca, P, Na) or passively through concentration
gradient. There are dozens of interactions between differentcompounds that
can affect absorption—for example, too much P will bind Ca, makingit
unavailable for absorption and causing calcium deficiency.
Also, excessive calcium will affect absorption of Mg (and vice versa),
excessive copper will affect iron and P, etc etc. Age of animalwill affect
absorption (older animals less efficient), also form of mineral, ieorganic
form vs inorganic form (inorganic generally higher, ie in forages,about 50%
of calcium is available, in limestone, about 75% available. Whenlooking at
NRC tables, they've already taken that into consideration.
Calculating ca:P ratio
Example:
Given 10 kgs of alfalfa (1.25%, 0.25%) and 4 kgs corn (0.05%, 0.3%)what is
ca:p?
10 kgs x 1.25% = .125 kg Ca 4 kgs x 0.05% = 0.002 => total Ca .127 kg Ca
10 kg x 0.25% = 0.025 kgs Ca 4 kg x 0.3% = .012 => totalP 0.037
Divide Ca/P => 3.43 (a little high but acceptable - 1.2 -2 better)
Example 2
Given 8 kgs oat hay (0.3%, 0.25%) and 1 kg rice bran (0.1, 1.7%)
8 kgs x 0.3% = 0.024 kgs Ca 1 kg x 0.1% = 0.001 kg Ca => totalCa .025 kg
(acceptable amt of dietary Ca)
8 kgs x 0.25% = 0.02 kg P 1 kg x 1.7% = 0.017 kg => total P .037kg (acc)
Divide calcium/P = .67 (not acceptable)
Minerals most commonly deficient in livestock rations are Ca, P, Mg,Na.
Understand differences between adequate and optimal:
adequate - no symptoms of deficiency
optimum - no symptoms of deficiency, plus additional improvement tohealth
or production
Example, adequate biotin will mean no symptoms which are cracks in hoof
wall, poor hair coat. Usually sufficient is synthesized by animalby
microbes, but may not be enough in some animals (such as animals onoral
antibiotic therapy). Additional biotin above adequate levelsresults in
higher hoof quality in horses.
Minerals aren't like that—you will get deficiency symptoms if mineralis
inadequate in the diet, but you will NOT get improved performance iffed
above requirement, and in many cases you get adverse reactions or toxicity.
Of these, animals will only actively seek out Na. Cafeteria stylemineral
supplements are bullshit.
There is no evidence that animals will develop a specific hunger forany one
mineral except for sodium.
Any mineral fed at levels either below or in excess of requirementsis going
to have some sort of affect on production, but most minerals in excessare
not toxic—you're just going to probably affect absorption of some other
mineral (thereby causing a deficiency of that mineral) or going towaste
money. Deficiency of a mineral is almost always going to be moreof a
problem than an excess of a mineral will.
Minerals that commonly cause toxic symptoms if fed at too high a level
include Se, Cu, Fe in neonates (newborn pigs are always deficient iniron at
birth, must be supplemented in confinement situations (no access todirt),
usually by injection with iron dextran or drenched ferrous sulfate,too much
causes death).
Se poisoning generally occurs in one of two ways; either the animalis
pastured in an area where the soil contains high Se levels, or toomuch Se
is supplied through supplement.
Look at handout where Se concentration in soils tends to be highestor
lowest. Areas of potential Se toxicity from the soil are mostcommon in SW,
and areas of the West (CO, NM, AZ, WY, east Utah, Montana, Nebraska,N/S
Dakota.
Plants have differing capability to concentrate Se, but conc'n in plants
will always be higher than conc'n in soil—so if conc'n in soil is highto
begin with, conc'n in plants is going to be sky high. In soilwhere conc'n
was 9 ppm, plant conc'n found to be as high as 1200 ppm.
Any soil where Se levels are above 0.5 ppm is dangerous and levels havebeen
measured as high as 40 ppm.
Chronic Se toxicity occurs in rations containing as little as 8.5 ppm,acute
poisoning occurs at 500-1000 ppm.
Young animals are especially susceptible (growth will be retarded evenif
level is too low to show other symptoms), swine 10 ppm will lower conception
rate and produce smaller, weaker litters.
Look at handout again at areas where Se is deficient. NW, FL,Great Lakes,
New England and all of the NE—Penn, NY, NH, NJ, CONN, RI, Maine, Vermont,
Mass, etc are all deficient in Se, which means Se must be supplemented.
However, too much of a supplement or premix can also cause toxicity.
Requirements for all livestock species is 0.1 - 0.15 ppm, rations should
contain ~0.3 ppm (mg/kg of feed).
Symptoms of toxicity are going to be loss of hair from manes and tailsfrom
horses or cattle, general loss of hair from swine, hoofs grow ringsor
slough off, feed consumption decreases so that animal may starve todeath.
Necropsy shows marked liver damage. If caught before goes toofar, take
animal off Se, liver regenerates, hair and hoof eventually grow back.
Copper toxicity - most likely to occur in sheep
Spp Req/Toxic
Cattle 5-8 mg/kg/115
Swine 6/250 (but sometimes increased growth response at 125,others dead)
Sheep 5/?
Poultry 4/?
Horses 10/Levels as high as 1000-2500 mg/kg tolerated
2800 mg/kg caused death after six months bydestroying liver and
kidney. May be due to decrease in Cu absorption as conc'n Cu increases
Copper absorption closely related to levels of Mo, zinc and S,high levels
of these three will increase tolerance to copper, as they decrease
absorption. Requirements 5 ppm, toxic less than 115, pasturesfetilized
with pig manure fed high copper was toxic to sheep.
Vitamins
Substances req'd in small amounts in the body, classified as water soluble
and fat soluble
Water soluble:
C
B-complex:
thiamin (B1), riboflavin (B2), niacin, pyridoxine (B6), pantothenicacid,
folic acid, cyanocobalamin (B12), biotin, choline, inositol,
paraaminobenzioc acid (PABA).
Fat soluble: A (retinol or retinoic acid, precursor carotene), D, E,K
Water soluble vitamins are required primarily as enzyme cofactors in
metabolism.
Vitamin A involved with vision and maintenance of epithelial cells,E is
metabolic antioxidant,
D involved in absorption and metabolism of calcium, K is a factor inblood
clotting.
Most vitamins that are stored are stored in the liver and other organs.The
fat soluble vitamins are stored to a much greater extent than watersoluble;
excess water soluble vitamins are excreted from the body within hoursand
most are not stored to any appreciable extent.
Species that maintain microbial flora are able to synthesize sufficientB
vitamins and vitamin K. Vitamins A & E must be provided inthe diet, as
well as vitamin D precursor, primarily ergosterol, which is convertedto the
active form of vitamin D in the body. Highest sources of vitaminD
precursor available in feeds is in sun-cured hays.
Vitamin A is not fed directly, must feed as precursor carotene. Carotene
content is very high in fresh, green pasture of any kind, but oxidizesvery
quickly, so that the carotene is essentially gone by the time it'scured and
fed. More than 80% of the carotene content is lost during thefirst 24
hours of the sun-curing process.
If hay is not sun-cured (dried in the barn) or is dehydrated through
artificial means, then carotene losses are only 30-70%, but the haystend to
oxidize faster during the storage process. The only hay thatwill still
have appreciable amounts of carotene is very green alfalfa. Thegreeness of
the forage is an indicator of the carotene content, but any table valuesof
carotene content are going to be estimates betcause of the extreme
variability in loss rates.
Heat along with exposure to oxygen accelerates oxidation, but heat without
oxygen has little effect. The only grain product with any measurable
carotene is corn and corn by-products, but still only about 1/8 thatof
forage. The only vitamin in premixes that is not guaranteed isvitamin A,
because of its ability to oxidize.