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!
 

Nutritional Management of Developmental Orthopedic Disease

DOD is also known as epiphysitis, osteochondrosis, angular limb
deformity—different manifestations of metabolic bone disease whichdisrupts
normal bone formation in young growing horses.  Most common inlarge,
fast-growing, light horse breeds, but can occur in any breed.

May manifest different ways, but all DOD are or are related to a failureof
growth cartilage to properly ossify into bone tissue.  When bonesare
growing, cartilage is laid down in growth plates either along diaphysisof
long bones or epiphysis at end of long bone.  Cartilage graduallycalcifies
into bone tissue.  If disturbed or disrupted, DOD results. Usually
diagnosed by swelling at joints and lameness, confirmed by radiographs.
Majority occur in limbs, or cervical vertebrae, though not all resultin
lameness.

Primary causes of DOD are
1) rapid growth (major cause)
2) trauma to growth plates
3) genetic predisposition (demonstrated in people, dogs, swine, horses)
4) nutritional imbalances - primarily energy, protein, calcium, phosphorus,
zinc and copper

Focus in this lecture is in horses, but also occurs in large breedsof dogs,
cattle, poultry and swine (big part of why all the pigs at the swineunit
are lame by the time they reach market weight).

Relationship between rapid growth and nutritional imbalance - let'ssay you
have a young animal that you are feeding a high energy ration. You get
rapid growth, but if mineral intake is not sufficient to meet additional
requirements, bone quality is compromised => DOD

DOD most commonly occurs in overfed horses, but can also occur in underfed
horses as result of inadequate protein.  Used to be thought thatexcess
protein was the cause, now we know this is NOT the case, at least not
directly.  Protein itself will not cause DOD, but if fed in sufficient
quantities, excess protein goes towards energy production, which will
contribute to DOD.   So excess protein is not the problem,excess energy is.

If insufficient protein is fed, with adequate energy, then the resultsare
decreased bone growth, but no decrease in weight gain.  This putsadditional
stress on the bone (trauma as listed above) and again predisposes toDOD.

Calcium-phosphorus imbalances - The primary minerals in bone tissueare
calcium and phosphorus, so no surprise that for optimal bone growth,you
need adequate Ca/P in the diet.  But, important not only thatminerals be
provided in diet, but that they be absorbed.  Many interactionsbetween
minerals, which may decrease availability.  Excess P will decreaseCa, but
also excess Ca will decrease P.  If diet/absorption is deficientin either
mineral, DOD might result.  In species other than horses, highcalcium also
decreases absorption of zinc, manganese and iron (zinc deficiency afactor
in DOD).

Copper-zinc imbalances - copper a factor in stabilizing collagen andin
elastin synthesis, deficiency may result in DOD.  Most commonlyaffects
ruminants, but also occurs in horses.  Animals with deficientcopper/zinc do
not have a decreased growth rate, just DOD lesions.  When copperand zinc
increased, growth rate still remains the same, but incidence of DOD
significantly decreases.  Therefore, copper and zinc do not affectgrowth
rate, just incidence of DOD.

Most common feeding practices which lead to DOD in young horses are:
1) feeding too much grain (excess energy)
 - continuous access to creep feed
 - feeding grain in excess of recommended amounts
 - why do people feed excess energy?
  - desire for animal to reach market size as quickly as possible
  - belief among horse owners that high energy plane will resultin bigger
mature horse (not true--if energy is sufficient, mature size will beequal,
just not as quickly)
  - desire for rapid, early growth in halter horses ( produceslarger
yearlings, but crippled two year olds)
2) unlimited access to legume hays such as alfalfa (excess energy and
excessive calcium leading to possible P deficiency)
 - source of excess energy unimportant, just as likely to getDOD from
excess alfalfa as excess grain (the important point is excess energy,not
where the energy came from)
3) feeding ration inadequate in utilizable calcium, phosphorus, copper,
zinc, protein (particularly lysine).

Recommendations to minimize DOD in growing horses:
1) Feed as much good-quality grass hay as will be consumed withoutwaste.
2) Legume hay:
 Weanlings: restrict legume hay intake to 0.5 lbs/100 lbs of expectedmature
weight.
 Example: You have a 6 month old weanling foal that you expectwill grow to
1200 lbs mature weight. => maximum alfalfa intake should be no morethan 6
lbs alfalfa per day.

 After 10 months of age, can feed an additional 1 lb per day until12 months
of age until 1 year.  Published recommendations state after 1year, can feed
ad libitum any type of hay.  I prefer limiting alfalfa until twoyears, and
ideally after that as well (preferably 25% or less of total forageration,
never more than 50% under any circumstances).
3) Grain mix:
 Nursing foals (age 0-4 months) - 0.5 - 0.75 lbs/100 lbs of presentBW
 Weanlings - (age 4-12 months) - 1.7 - 2.0 lbs/100 lbs of BW
 Yearlings (12-18 months) - 1.3 - 1.7 lbs/100 lbs of BW
 Long yearlings (18-24 months) - 1.0 - 1.25 lbs of BW
 two-year-olds (24-36 months) 1.0-1.25 lbs/100 lbs of BW

NEVER feed more than 0.9 lbs of grain per 100 lbs of expected matureBW
(this takes precedence over above recommendations).

Example: You have a 16 month old yearling that weighs 800 lbs, thatyou
expect will mature at 1100 lbs.  Based on 1.3 - 1.7 lbs of grain/100lbs of
BW, you should be feeding 10.4 - 13.6 lbs of grain per day.  However,based
on a mature body weight of 1100 pounds, this horse should be fed nomore
than 9.9 lbs of grain (11 x .9 = 9.9)

4) Make sure grain mix/total ration is properly formulated to provide
adequate minerals in correct ratio
 Requirements: Protein, Ca, P, Cu, Zn
Nursing   16%, 0.9%, 0.6%, 60 ppm, 50 ppm
Weanling   14.5%, 0.8, 0.5, 60, 25
Yearling   12.5, 0.5, 0.3, 40,  25
Long yearling  12, 0.4, 0.24, 40, 10
Two year old  11, 0.3, 0.20, 15, 7
Mature   8, 0.25, 0.20, 15, 7

All of the above nutrients are on a dry matter basis, NOT as-fed.
There is no harm in adding more copper/zinc (this applies to horsesonly,
not other species), so rather than calculating how much copper/zincis
already present in forage, recommended to just add additional copper/zincat
above levels.

Yeast cultures - research by Glade demonstrated that addition of yeast
culture Yea-Sacc decreased incidence of DOD in young, growing horses.
Hypotheses is that microbes secrete phytase, which increases P
bioavailability and absorption.  Recommended addition to younghorse
rations, especially those at risk of DOD.  Species investigatedwas
Saccaromyces cerevisiae (brewers yeast).  There is a differencebetween live
yeast cultures and dead yeast cultures.  Brewers yeast is dead,no probiotic
benefits.  Yeast culture is live (freeze dried), reconstitutedwhen
introduced to aqueous/warm environment.  Also increases butterfat
production, increase fiber digestion.  Two latter benefits areprimary
advantages in supplementing other livestock species.

In poultry species, probiotic cultures are being used to decrease
Salmonella.  Newly hatched chicks are sprayed with probiotic solution. When
chicks preen, GI tract is colonized with "friendly" bacteria, whichcrowd
out Salmonella species.  No Salmonella in GI tract means no contaminationof
eggs and less incidence of contamination of broiler carcass (thoughboth can
still be contaminated from other sources).