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AN SC110 Lecture Notes - Foal, Chromosome, Umbilical Hernia

Animal Science
Course Code
AN SC110
Doug Milligan

of 6
Lecture 1 for final November 15, 2011
**assignment due December 6**
Considerations BEFORE breeding
Identify weaknesses + strengths able to select for
things, its hard to select for things if you don’t know
what they are! Can be subjective
Environment reared Want a cow horse? Rear around
cows. They will be best suited to work in an
environment that they are reared in.
Special care + training have the genes and the form
to function soundly, put them in the hands of the best
trainers so they have the best opportunity to run as
best as they can. Can be a bonus to allow us to identify
the best horses. If a super horse is in poor hands, we do
not know the capabilities of the horse may have in the
breeding shack. .
Pets no room for pets in the breeding industry!
Stallion or mare must prove themselves to be worthy of
breeding ( right genetics, capabilities etc)
Capabilities breeding horses to function and form, lets
ensure they have the correct capabilities. Ex sport
horses, hunters + jumpers. Commercial-ness is in BIG
horses (16-17) hands
Breeding Systems
Grading up want to breed a mare to a stallion that is
BETTER than her. Ensures next generation is better
Cross-breeding mate individuals of two different
breeds( hunters are often thoroughbreds +arabs).
Creates heterozygosity, prevents genetic defects +
increase soundness
Out-breeding WITHIN the same breed, but individuals
are not related (NO common ancestors)
In-breeding have at LEAST 1 common ancestor on
both sire and dam side. Creates homozygosity, brings
genes together, increases predictability. IN breeding
fixes a particular trait ( homozygous). Cannot
select for it anymore. Its there,
Line-breeding in breeding, but concentration the
genetics of a particular individual back down the
Effect on Progress
Number of traits
Heritability measures degree to which progress is due
to genetics. Measures the percent of the trait that is
controlled by the genes. What portion of the end result
is due to genetics. Takes out environment
Size of herd more foals to pick from, better chance for
progress as you can pick the best stock
Starting level start lower, more chance and room for
improvement! You must know where you are. To be
commercial you must have horses that are moving up.
culling rate be very strict. Removal of inferior animals
from breeding stock
-if you do not provide the proper environment, it does not
matter what sort of genetic background a horse has, he wont
live up to it
-If you have a horse with poor poor genetics, it doesn’t
matter what you give him, he will not be better than his
Three equine familes 32 chromosomes
2.ass/donkey 31 pairs of chromosomes
3.zebra 16;23;22
all will interbreed and produce offspring. Why are the babies
sterile extra chromosome! 31 pairs and 1 extra. Because
they do not have a complete chromosomal compliment.
50/50 genes from dam and sire.
50% related to FULL brothers and FULL sisters. Only half of
the same genes. Full siblings can go onto very different
twins basically full siblings that happen o be born a the
same time, NOT full genetic matches
Most genetic disorders are recessive, and dominant genes
can mask this. That is why often times in-breeding will bring
out these genetic disorders
Homozyous two dominant or two recessive
Heterozygous one dominant one recessive
Prepotence has ability to express his likeness on the
offspring. High % homozygous dominant. If this animal
is bred to another animal, it will express this likeness
regardless of whom he is bred to.
Linked Inheritance
Appaloosa colouring. If you want the coloruing, you get
the rest
White sclera
Striped hooves
Mottled skin
Males always determine sex ( XX, XY)
Sex-linked inheritance
Hemophilia inherited as recessive, more in
males as opposed to females, Y chromosome
carries very little genetic information. If male gets
it, must be expressed, if female, you need two
homozygous genes
Lethals carried on X chromosome, females have
another copy to express, males are screwed.