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!
 

Feed Preparation and Processing

Feed represents major cost in livestock production:
 55% in sheep (cheapest)
 75-80% in poultry

Important to provide feed that will provide adequate nutrition while
encouraging consumption with minimal waste.

Feed processing methods may be chemical, thermal, mechanical (or
combination)
Processing may also include microbial fermentation ,ie ensiling

Processing does one or more of the following:
alters physical form of particle size
prevents spoilage
isolate specific parts of a seed or plant (separate corn grain fromplant,
but also corn starch from grain)
improves palatability
inactivate toxins or antinutritional factors
improve handling (chopped hay can be fed more easily by mechanicalfeeders
than can baled hay)

Processing becomes more important as level of production increases (whenmax
production is desired)
Not so important in band of sheep on rangeland that don't need to growat
any specific rate
Very important in intensive production such as poultry, swine confinement
operation, dairy

Why, because heavily fed animals more likely to sort through feed andpick
out only the feed they like, or to refuse/waste feed if they don'tlike it.

Also, in ruminants, efficiency of digestion decreases as level of
consumption increases.  This because food moves too rapidly throughrumen
for maximum fermentation and extraction of nutrients.  Processing
counteracts part of this decline in digestion

Processing of grain can be divided into wet/dry methods, hot/cold methods

Cold-processing:
Hammer mill grinding - most common processing method.  Used forboth grains
and roughages.  Hammer mill is rotating metal bars that blowsground feed
through a screen, the finer the screen used, the smaller the particlesize.
Can produce anything from a cracked grain to a fine dust.  Particlesize is
important because the smaller the particle size, the more SA you'reexposing
to digestive enzymes and microbes, but—ruminants and horses don't like
eating very small particles, okay for poultry and swine.

Roller mill cracking and grinding - used only for grains, not roughages.
Grain goes between two metal rolls, particle size controlled by howfar
apart the rollers are.  Particle size range from cracked grainto fine
powder (fines).  Does produce as much dust as hammer mill processing,but
doesn't grind hulls as well as hammer mill.

Soaking and reconstitution - two similar processes, where grain is soaked
prior to feeding.  In soaking, feed is soaked in water, sometimeswith heat
for 12-24 hours.  Increases palatability, but not marked increasesin
digestibility.  In reconstitution, enough water is added to wholegrains to
increase moisture content to 25-30% and kept in oxygen-limited silofor
14-21 days.  Some fermentation takes place.  Increases palatabilityand feed
efficiency, but not enough to warrant the amount of work and storagespace
required.

High Moisture Grain - Grain harvested at high moisture content (20 -35%),
sometimes ground or rolled, treated with 1 - 1 ½ % acid andstored in a silo
or under plastic.  Acids used to preserve are primarily propionic,or
mixture of propionic with acetic or formic acid.  Feed efficiencyis higher
than for dried grains (no matter how dried grains are processed), butharder
to store and transport.  Mostly used when weather conditions don'tallow for
complete drying of grains in the field prior to harvesting.  Candry grains
artificially, but may be more expensive than storing as high-moisturegrain.

Hot processing methods:

Includes steam rolling/flaking, extruding, pelleting.

Steam rolling/flaking - in rolling, grain is exposed to hot steam for5
minutes before rolling to soften grain.  In steam flaking, steamedfor 15-30
minutes.  Steam rolling has increased feed efficiency over drygrains, steam
flaking higher feed efficiency over steam rolling (exception barley-steam
rolling just as good as flaking).  Both, better physical texturesas fewer
fines, so ruminants like them better.

Pelleting - feed is ground, usually steamed (not always), then forced
through dies to produce pellets.  Good use for fines that otherwisemay not
be eaten.  Animals like texture pellets more than they do a meal,less waste
in windy areas because fines blow away.  Improvement in feed efficiencyis
due to grinding, not due to pelleting—the pelleting just makes thetexture
more appealing to the animal.

Extruding - process where feed is ground, heated and forced througha head
to form a long ribbon which is then chopped into desired particle sizeis.
Used commonly in pet and human foods.  Used with soybean products,because
heat is enough to destroy antinutritional factors in raw soybeans. Soybeans
contain several different compounds that inhibit amino acid utilization,
decrease protein digestibility or are goitrogenic factors, but allcan be
destroyed by heat.  So soybeans are always heat-processed beforebeing fed
to livestock (or pets or humans), extruding is one method.
 
 

Effect of processing on nutritive value:

Heating - excess heat causes Maillard reaction, reaction between proteins
and carbohydrates in feeds, lysine becomes partially unavailable. Primarily
a concern in plant protein sources (SBM, CSM< alfalfa, etc) or milk
products, as other animal source feeds don't have enough carbohydrates
present to cause reaction to any significant extent.

Excessive heating of animal or fish proteins decreases feeding value
Heating of cereal grains gelatinizes starch content and increases feeding
value in dogs, cats, pigs, poultry, but not for ruminants or horses

Any processing method which increases surface area exposure to light,
oxygen, heat, etc is going to decrease vitamin content.  Vitaminsmost
susceptible to heat are fat soluble vitamins (, thiamin, pantothenicacid,
folic acid and biotin.

Excessive heating of fats releases acreolins and increases oxidation=>
rancidity

Processing for specific species:

Swine: grinding and pelleting most common processing methods. Increases
digestibility, decrease in sorting.  Max feed conversion (numberof pounds
of feed required per pound of gain) produced with fine grinding (.16cm
screen), also develop stomach and esophageal ulcers, so medium grind(1.27
cm) better.

Screen size  0.16 1.27 2.54
ADG, kg   .65 .63 .63
Feed conversion 3.19 3.56 3.67

Pelleting - 9-10% improvement in feed conversion, gain weight at samerate,
but eat slightly less and waste less.  Pigs like physical textureof
pellets, eliminates sorting.  Alfalfa is primary roughage fed,but because
of limited ability to digest roughages, relatively small portion ofration.
If fed as hay or meal, pigs tend to waste a lot, so usually incorporated
into pellet.

Horses - Pelleting, cubing feeds has very little or no effect on rateof
digestibility in horses.  In horses with good teeth, no increasein
digestibility by flaking, cracking, etc.  The advantages in
processing/pelleting feeds is to decrease waste, eliminate sorting,allow
use of fine particles (horses don't like fines), and easier handling,
transport and storage:

Ton of hay cubes occupies 60-70 cubic feet storage
baled hay 200-330 cubic feet
loose hay 450-600 cubic feet

Horses eating pelleted hay also produce less feces, less labor costsin
cleanup.  Less feces is not due to increased digestibility ornutrient
retention, is due to decreased (6% less) water content (theory of increased
chance of feed impactions)

Increased feed intake because of less gut fill, useful if you need
additional feed intake or don't want "hay belly" look in show horses.
Horses can be fed 100% of their ration as pellets or cubes without
physiological harm.  However, feeding pellets = decreased feedingtime ( 25%
less time to eat pellets than same amount of loose hay).  Mayincrease
incidence of choke, although uncommon problem.

In cattle, feeding all pellets or cubes may produce progressive enteritis,
not investigated in horses, but indications that may be true for horsesas
well.  Prevented by 25% of forage ration as hay.

Feeding pellets doesn't satisfy grazing instinct, so increase in wood
chewing four times over that in horses fed loose hay or cubes. Recommend at
least 25% of ration in the form of long-stem hay to satisfy grazinginstinct
and provide entertainment.

Poultry -

Majority is fed as mash, pellets or crumbles.  Mash is a mix offinely
ground feeds, crumbles are a pellet that have been put through rollersto
partially break it down (it's cheaper to make a large pellet and thenroll
it, than to make a small pellet in the first place).  Advantagesto feeding
pelleted/crumblized feeds are same as before (increased feed efficiencyof
about 2 - 5%), disadvantage is that with pellets, increased featherpicking
and cannibalism, also increase in water consumption.

Beef Cattle - processing of feeds is unimportant when roughage accountsfor
the majority of the diet.  As roughage intake decreases and concentrate
intake increases, processing becomes more important.  In feedlots,grains
account for 70 - 90% of the total intake.  Almost any processingmethod
which breaks up the grain kernel results in increased digestibility,so
cheaper methods (such as rolling or hammer mill) are just as good asmore
expensive methods (such as methods using steam, or extrusion, etc).
Greatest increases in digestibility are in hard grains - oats (a soft
grain), 4% improvement.  Barley and wheat (hard), 33% and 25%,respectively.

Processing of roughages for beef cattle - there is no appreciable feed
efficiency by just chopping or grinding roughages.  Cubing orpelleting
produces small increases in feed consumption, also less waste and sorting.

Pellet size not important except in young calves, needs to be smallenough
so they can eat it easily.

Dairy cattle - processing of feeds results in a shift of VFA production,
which in turn affects milk production.  Rations that are morethan 60%
grain, or in which all of their roughage is ground,  pelletedor cubed
reduces acetate production in the rumen, which in turn depressed butterfat
production in the milk.  Rolling or grinding grains is all dairycattle
really need.

Sheep and goats - because of the increased costs, feeding processedfeeds is
generally very limited, such as when ewes are brought inside to lambduring
the winter, sometimes to young, fast-growing lambs.  Advantagesthen are
primarily ease in handling.  When maximum production is wanted,then
pelleting feed increases consumption by about 40%.  Pelletingcauses VFA
shifts in the rumen, produces a softer fat.