FLORIDA AGRICULTURAL EXPERIMENT STATION
Dairy Science Mimeo Report DY65-2
June 10, 1965
J. M. Wing and C. J. Wilcox
Repeat breeders cost their owners at least an extra dollar a day.
Hence, careful planning of the breeding program is one of the most
important jobs at the dairy or ranch. Whether breeding is accomplished
through artificial insemination or natural service the following
physiological fundamentals should be considered.
1. Most cows stay in heat about 14 hours, but individuals vary
from 6 to 36 hours.
2. The egg is shed from the ovaries of the cow 7 to 15 hours
after the heat period has ended.
3. Fertilization must take place right after ovulation for best
4. Spermatazoa are propelled through the genital tract mainly by
muscular contractions. These movements occur properly only
if the cow is comfortable, healthy, is not excited, and is in
or very close to the heat period.
5. Wherever sperms are deposited in the genital tract, some of
them reach the site of fertilization within a few minutes.
They must be conditioned for about 6 hours, however, by the
female fluids before they are capable of uniting with the ova.
They should be at the distal end of the female tract and
should have been deposited long enough to be conditioned by
the time of ovulation. Thus six hours before ovulation is
the ideal time to breed most cows.
6. The sperms may be shocked, thereby losing part or all of their
effectiveness by (a) direct sunlight, (b) cooling too rapidly,
(c) contact with chemicals including soap or the residual
sulfur in rubber parts, (d) pulling them into the inseminating
tube too quickly, or (e) driving over rough roads too fast.
7. About 60 days are required for the genital tract to recover
8. About 10 per cent of all cattle are likely to be unable to
conceive without treatment.
9. Most spontaneous abortions occur at 4-1/2 months and most
premature births are at about 7-1/2 months of pregnancy.
10. Retained placentas may be caused by very mild to very severe
abnormalities of the uterus. Cows exhibiting retained
placentas or metritis at calving can be returned to normal
by prompt veterinary attention. Premature births or the
birth of twins often cause retained membranes.
Based on these fundamentals, the responsibility for the breeding may
be apportioned approximately as follows.
A. The herd manager should:
1. Keep records of heat periods, breeding and calving dates,
difficult births, retained placentas, abortions or other
health data, and decide when each cow should be bred,
2. Call the technician in time for him to arrange the proper
time for breeding.
3. Provide catch pens for heifers and a shady, clean place
4. Isolate cows to be bred and keep them as calm and comfortable
5. Wash the external portion of the reproductive organs.
6. Handle animals carefully at all times but especially at
4-1/2 and 7-1/2 months after breeding.
B. The inseminator should:
1. Examine the semen at frequent intervals using a good
2. Keep the semen at the proper temperatures (40F for liquid
and -1100 or -320F for frozen semen).
3. Keep equipment clean. Wash all instruments with soft water
and an inorganic phosphate cleaner (not soap or detergent).
Rinse well in tap water then in double distilled water.
Dry in a dust free place.
4. Rubber parts are scrubbed then boiled in soda water to
neutralize any sulfur which may be present.
5. Use mineral oil or other nontoxic lubricant (preferably
6. Handle semen carefully to prevent physical shock.
7. Keep semen out of direct sunlight.
8. Breed all animals quietly and quickly.
9. Use deep cervical deposition rather than entering the
uterus with the inseminating tube.
10. Use fresh semen as soon as it is removed from storage and
frozen semen as soon as it thaws.
11. Keep finger nails very short and never wear rings or other
possible injurious jewelry.
12. Disinfect boots before leaving each farm.
Number 12 applies also to the veterinarian who in addition should be
1. Examine unbred heifers four to six weeks before the breeding
season to detect and treat potential causes of difficult
2. Examine all bred cows just before the second expected heat
since some cows which are with calf will come into heat
and these must not be bred again.
3. Examine all bred cows for pregnancy before 60 days have
elapsed after breeding.
4. All cows should be examined shortly after calving, especially
if difficult calving or retained placentas are reported.
When these precautions are observed, at least nine out of ten cows
will conceive to one of the first three services. The remaining ten
per cent should be examined and treated if advisable. Any cow which
still is open after five breeding should be culled except in special
cases where further therapy is promising or the animal is particularly
valuable. Problem cows which are producing at profitable levels
should be subjected to insemination regularly. In the case of unusually
persistent high producers this could amount to several additional