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!
Fats
Livestock species do not require additional dietary fat beyond theessential
FAs naturally occurring in feeds. However, fat is very commonlyfed to
livestock for several reasons:
1) Reduce dustiness
2) increases palatability
3) Decreases wear and tear on milling machinery in feed mills
4) Fat in the diet increases the absorption of fat soluble vitamins- in the
presence of additional dietary fat, the body responds by manufacturing
additional lipases enzymes, which act not only on the dietary fatsbut also
on fat-soluble vitamins, thereby increasing their absorption
5) provides additional energy to ration - fats provides 2.25 timesthe
energy of carbs and are the only feed that provides only one nutrient(with
exception of some fat soluble vitamins). No protein, no minerals,just
energy.
Fats for livestock can come from either animal or vegetable sources,both
are very well accepted and digested by livestock species.
40% of the raw fat fed to livestock comes from spent restaurant grease
21% comes from shop fat and bone (trimmings from supermarkets, restaurants,
etc)
19% packing house offal (more or less the same thing)
9% fallen or dead animals
6% poultry offal
4% other things
Vegetable oils are generally too expensive for use as animal feed, usually
only available as either by-products of refinery (acidulated soapstock)or
as vegetable oils once "spent" as restaurant grease. Raw sourcesare
usually processed, and blended, provided as feed-grade animal/vegetablefat.
Also available as calcium salts - calcium molecule bound to long chainfatty
acid from animal sources. Still 100% fat, highly digestible,can be coated
with flavorings to further enhance palatability. Marketed asEnergy Booster
100 for swine and dairy rations, can be used for other livestock speciesas
well.
The more fats are exposed to oxygen and heat, the more they become oxidized
=> rancid. Decreases palatability, cause digestive upset, alsodecreases
the availability of other fat soluble vitamins in the feed. Antioxidants
are almost always added to feed grade fats, especially if the fat isgoing
to be stored for any length of time. However, feeds that containadded fat
should be fed as quickly as possible, because antioxidants will nottotally
prevent oxidation. If fat is provided by individual owner (iehorses), then
fats should be kept in containers so that exposure to light, heat andoxygen
is minimized—if you buy big jug, pour off small amounts into smaller
bottles, keep jug closed and in cool, dark place.
Fat is usually added to swine grower rations at 5-10%, used sparinglyin
finishing rations because adds too much backfat. Also, compositionof fat
affects fat deposition in swine (and poultry) carcasses. Degreeof
saturation and length of the carbon chain dictate the hardness of thefat.
Saturated fats produce saturated (harder) fat deposition. Unsaturatedfats
produce softer carcass fats (undesirable). This effect does notoccur in
ruminants because rumen microbes saturate all fats. However,if bypass fats
are used, then effect may occur.
Fats are usually added to poultry rations at about 2-4%. Levelsabove 10-12
produce reduction in feed consumption (because animal eat to meet their
energy requirement). Reduced feed consumption is okay, as longas they're
still consuming sufficient amount of other nutrients. So if highlevels of
fats are fed, concentration of other nutrients usually must be increasedto
supply requirements.
High levels of fats are only fed to cattle in milk replacers, usuallyto
veal calves. 10-30% of ration. Can be fed to calves without worrying
effects on rumen, because at that age, they don't have a functionalrumen,
anyway. In mature cattle, levels more than 7-8% produce diarrhea,reduced
feed intake. Fat kills off the microbial population, so benefitsby dding
fat are more than offset by detriments to feed efficiency in digestingother
feeds.
Fats are usually added to equine rations for one of two reasons
1) Show people feed to add bloom to the coat
2) add or maintain weight in horses with large energy requirement
Research study that looked at the quality of the hair coat in horsesthat
had fats added to the diet, horses that did not have fats but weregroomed
daily and horses that had nothing added to diet and were not groomeddaily.
Horses that had no fat added beyond what was present in a good dietbut were
groomed daily had best hair coat.
Fats can be added to the diet up to 20% of the total diet, or up to30% of
the concentrate ration, but around 10% of the concentrate ration ismore
common. Beyond 10%, you have to work harder to get the horseto eat it,
because some horses don't like slimy texture of liquid oil (ester saltsare
good substitute, especially if flavored).
Fats fed to performance horses still subject of a lot of argument and
research, but there are some things we do know:
1) feeding fats increases energy density of the diet. Horses willeat 2-3%
of their BW daily, beyond that cannot stuff it down fast enough. If you
have a horse that is eating the maximum amount of food and is stilllosing
weight, then you have to increase energy density (or number of caloriesper
pound of feed). You can do that by adding a more energy-densefeed such as
grain, but feeding too much grain increases risk of grain overload.
Fat is the most energy-dense feed available, so adding fats will domore to
add calories than any other feed. Because fat is so highly digested,energy
available for production is increased by 60% even when energy intakeremains
the same.
Remember GE => DE => ME => heat increment => NE (energy available for
production)
Very little of the gross energy in fats are lost through fecal, urinaryor
heat increment losses, which means that most of the energy is availablefor
production.
As a general rule of thumb, fats will provide about three times more
available energy than an equal weight of cereal grains, and 3.5-6 timesmore
energy than an equal volume of cereal grains.
2) fats decrease heat load, because there is no heat increment (thebody
does not produce any waste heat in metabolizing fats, as it does forprotein
or fiber). In a study where 10% fat was added to the diet, heatproduction
was decreased by 14%. This is an important factor for horsesin hot
climates, living in stalls or that perform sustained exercise in heat.
3) not yet totally explained, but research indicates that performancehorses
fed a 10% fat ration produce a "glycogen-sparing effect". Feedingfats
beyond 10% don't provide additional glycogen-sparing effect, just addsmore
calories.
Glycogen is the storage form of carbohydrates in the body, specificallyin
muscle cells and liver. Stored in extremely limited amounts,technical
definition of fatigue is in part glycogen depletion. During exercise,body
uses two basic substrates, glycogen and fat. The body can utilizeglycogen
without the presence of fats, but cannot utilize fats without the presence
of glycogen. So once the glycogen is totally used up, energyproduction
stops until glycogen can be replaced, which takes several hours toseveral
days. So in horses that have to perform repeated bouts in a singleday or
over several days, conservation of glycogen is important.
Glycogen sparing effect means that during performance, horses will relyless
on glycogen for energy and more on fats. Fats are available invirtually
unlimited supply, and less likely to deplete glycogen supplies.
How to calculate fat % in a diet:
Example: You have a 1000 lb horse that is currently consuming 15 lbsof hay
(1 Mcal/lb) and 15 lbs of grain (1.5 Mcal/lb)(37.5 Mcals) and is still
losing weight. How can we increase the calories in his diet?
1) You could decrease his hay and increase the grain? No—ruleis don't
increase grain above 50% of the total ration. Also, you alwayswant to
provide 1-1.5 pounds of hay for every 100 lbs of BW.
2) Increase both hay and grain, just put more food in front of him.
Nope—horses can only consume between 2-3% of their BW on a daily basis. 15
lb hay + 15 lbs of grain = 30 lbs a day of food => 3% of 1000 lbs,so this
horse physically can't stuff any more food down his face.
3) Replace concentrate ration with more energy-dense feed (fat). Let's say
you decide to add fat to produce 10% fat diet. 10% of 30 lbs = 3 lbsof fat,
so you would replace 3 lbs of grain with 3 lbs of fat.
Now your horse is still eating 30 lbs of food per day, but instead of37.5
Mcals of DE, now you're providing:
15 lbs hay x 1 Mcal/lb = 15 Mcals
12 lbs of grain x 1.5 Mcals = 18 Mcals
3 lbs of fat @ 4 Mcal/lb = 12 Mcals
Total = 45 mcals DE, 20% increase.
Garbage as an energy source—not the stuff from trashcans. Leftoverfood
from restaurants or other food institutions (cafeterias, hospital kitchens,
etc). Only feasible near large cities where daily pickup is practical.
Must be cooked to minimum temperature to kill pathogens, such as Salmonella,
Trichinella and tuberculosis (all of which can be transmitted to pigsand
then back to humans through the carcass).
The practice of cooking pork to "well-done" is to kill pathogens, butnot
necessary when pork is from commercial pork producers and meat processors.
Reported cases of trichinosis, etc are today invariably from home-raised
pork fed raw (uncooked) garbage or from bear meat (who often feed onhuman
garbage). However, contamination of the carcass after processsingcan still
occur (Salmonella and Staph), so should still be cooked to 170 degrees
Fahrenheit internal temperature.
Garbage varies in nutritional content, usually must be supplementedwith
additional energy and protein sources. Garbage is not fed toany other
livestock species except swine.
Summary of high energy feeds - highly digestible source of primarilystarch,
simple sugars or fats, depending on source. Moderate in proteincontent,
generally low in Ca and moderate to high in P. Vitamin and tracemineral
contents varies.