The Rural Voice, 1983-08, Page 38Westward Tools
All grades of nuts and bolts
Epps Pressure Washers
KETO Abrasives
Scott's Industrial
& Farm Supplies
R.R. 4, Tara
519-376-0283
8 miles west of Owen Sound
off Highway 21
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Location:
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R.R. 3,
Goderich,
Ontario
519-395-3300
Division of
PARRISH & HEIMBECKER LTD.
PG. 36 THE RURAL VOICE, AUGUST 1983
ANIMAL SCIENCE
E.T. - the
wave of the future
Few people could help but laugh at a
research scientist's recent prediction that
dairy cows might some day be as large as
elephants with an annual milk production
of 45,000 pounds. Yet only a few years ago
embryo transfers in cattle also seemed
impossible. So did accurately identifying
the sex of an embryo, test tube breeding,
transferring genes from one species of
animal to another and even the now com-
mon technique of embryo freezing.
Technological advances in the livestock
research industry occur with such amaz-
ing frequency these days, it is virtually im-
possible to stay current from one month
to the next. Caught up in this excitement,
many cattle breeders have enjoyed "trying
their luck" with embryo transfer (E.T.) in
recent years. After all, E.T. offers the true
animal breeder an exciting avenue to
genetic advancement.
Let's examine some factors to consider
when contemplating the use of E.T. in
your program and particularly the selec-
tion of a donor cow.
A donor cow should have:
Regular estrus cycles commencing at a
young age.
Need of no more than two breeding ser-
vices per conception.
Superior individual performance traits of
economic importance.
Above average productive performance of
offspring from previous matings.
No parturition difficulties or reproductive
irregularities.
No conformational or detected genetic
defects.
The age of the donor is a "give and
take" situation. The younger you use a
cow, the faster you turn a generation in-
terval. The faster you turn a generation in-
terval, the more progress you are making.
On the other hand, the older the cow is,
the more you know about her and the
more predictable she is. The choice must
be made with your goals in mind. If you
want to breed a taller cow, you should use
your tallest yearling heifer. If she is from a
tall bull and you breed her to a tall bull, the
chances are that the calf will be tall. But
you will not know how she will milk,
whether she can calve by herself, what her
udder will be like or whether she will be
generally sound.
So if you are Interested in function, it
would be better to let her raise her first
calf and possibly her second to see if she
rebreeds. There is some predictability of
function and, in my opinion, a three -to -five
year old animal allows an adequate
generation interval basis. Every breeder
will have his own reasons for transplan-
ting a given cow. Reasons are often more
economic than true genetic superiority
and are often influenced by sire selection.
The thing to look for as far as a sire is
concerned is a greater amount of predic-
tability. The risk is great when an un-
proven sire is used in embryo transfer. The
use of semen of known quality by trained
personnel is an essential part of any suc-
cessful program. This is a mangement
task and on a practical level, once the
selection of the sire and donor has taken
place, management and attention to
detail greatly influence the degree of suc-
cess of the program.
Timing, records and nutrition are
management factors the producer must
fully understand and implement for on -
the -farm programming. Timing, as it
relates to injection intervals and the
observation of estrus are very necessary
at the time of embryo transfer.
Finally, if there is a factor that, in our
experience, has a most dramatic effect on
the results obtained, it is the nutritional
levels of the donor and recipient animals. I
cannot over -emphasize the importance of
nutrition as it relates to embryo transfer.
Each ration will vary, but to ensure the
availability of necessary nutrients is a
relatively simple matter which must occur
early in the planning stages of any pro-
gram.
The value of E.T. in the genetic improve-
ment of livestock can be easily seen and
the acceptance of this procedure with its
advantages and limitations is rapidly oc-
curring. The economic value of E.T. offspr-
ing will determine its usage. We are now
able to freeze embryos for future recovery
and the advancements continue.
Researchers at Britain's Cambridge
University have joined an embryo and an
unfertilized egg to create a mouse with
three parents, while a Maine researcher
has created mice with no fathers by fer-
tilizing mouse eggs and then "plucking
out" the genetic material contributed by
the sperm. Ei
Dr. Rae S. Fischer, D.V.M.
Embryo Transfer
Listowel Veterinary Clinic
Listowel, Ontario