Agriculture Reference
In-Depth Information
SOME UNDESIRABLE RECESSIVE
TRAITS IN SHEEP
ABNORMALITY
DESCRIPTION
Lethal defects
“Daft lamb”
Brain isn't fully developed. Lambs are born alive but are usu-
ally unable to walk due to poor balance.
Dwar fi sm
Short legs, thick shoulders, bulging forehead. Lambs usually
only live a week or two.
Earless and cleft palate
Affected lambs are born alive but die quickly.
Lethal gray
Lambs die early due to digestive disorders.
Muscle contracture
Lambs are usually stillborn. Limbs are rigid.
Paralysis
Hind limbs are paralyzed. Lambs die within a few days.
Spider Lamb Syndrome
(SLS)
Also known as ovine hereditary chondrodysplasia, SLS is a
genetic disorder causing skeletal deformities in young lambs,
including abnormally long, bent limbs; twisted spines; shallow
bodies; fl attened rib cages; and long necks. Most lambs die
shortly after birth.
Nonlethal defects
Cryptorchidism
One or both testicles do not drop down into the scrotum
(associated with polled trait in Merino and Rambouillets).
Earless
In Karakuls some lambs may be born with no ears and some
with short ears.
Inverted eyelids
This trait is highly heritable and widespread among breeds of
sheep. The eyelids turn in, bringing the eyelashes into direct
contact with the cornea. This contact irritates the eye, making
it necessary for the animal to blink constantly, which simply
aggravates the problem. It can be treated if caught early.
Naked
Lambs are born with a few hairs and black shiny skin. Lambs
grow adequately, but they are sensitive to temperature
changes.
Skin folds
Most often occur in fi ne-wool breeds.
Yellow fat
Yellow carcass fat, which is objectionable in some markets.
there are lots of sex cells in each parent's reproductive tract, with half the cells
carrying one string of code and the other half carrying the other string.
At conception, a sperm cell fertilizes an egg, and the resulting cell (called a
zygote) has a full complement of genetic material for its species. It is a matter
of chance that determines which half of each parent's genetic code is brought
to the mating, but there are just four possible combinations of alleles for each
gene pair from any pair of parents.
 
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