Equine Reproduction
Dr.
Jack Sales, DVM
Assignment:
Read Chapter 18 in the text.
This is the last lesson for this course.
In this chapter you will be exposed to a variety of record keeping techniques
that have been proven to greatly increase the effectiveness of breeding farm
management.
Good records are extremely important to
the smooth running of a horse breeding operation, and can be used very
effectively to alert the management to possible problems. A big part of the effectiveness of good
breeding records is the regular scheduling of record analysis. The following
outline will serve as a study guide and overview of the important aspects of
Chapter 18.
1. Individual
stallion records.
a. Daily
breeding reports – a must for all breeding facilities.
b. Routine
semen evaluations. This is done every other day on many artificial insemination
farms, but may not be done often enough on a live cover operation. It is vital
to be up to date on the semen quality of all your stallions during the breeding
season.
c. Routine
veterinary medications or reports.
d. Notes
on stallion behavior.
2. Stallion
service reservation list.
a. Daily
breeding report.
3. Individual
farm mare records.
a. Daily
teasing, exam and breeding records; a must on all breeding farms.
b. Foaling
records.
c. Suckling
foal records.
d. Routine
vet treatments and medications.
e. Farm
daily logs.
4. Individual
outside mare records.
a. Owner
statements and mare history. This should
be required when a mare is sent to the farm.
b. Breeding
contract.
c. Health
and breeding soundness certificates. (Negative culture and Coggins.) This is
another must for outside mares.
d. Arrival
and departure records.
e. Records
“a” through “e” under farm mare records.
The chapter on breeding records has some very good examples of different
types of forms that can be extremely helpful in a good record keeping system
for a breeding farm.
1. Seasonal
pregnancy rate. The number of pregnant
mares/the number of mares bred times 100. (The number of mares pregnant on a
specific day divided by the number of individual mares bred to that date.)
a. For
the farm, for the year or season.
b. To
a certain date.
c. By
types of mares.
1.
Barren
2.
Foaling
3.
Maiden
Example:
For the year 2004 (breeding
season 2004) let’s say on
July 30 it was determined that
of the 20 individual
mares bred during that season,
17 were found to be
pregnant.
Seasonal pregnancy rate as of
17/20 =.85 x 100 = 85 per cent.
If these same 20 mares were
checked for pregnancy
again
on November 30 and 15 were found to be pregnant
the seasonal pregnancy rate for
the 2004 breeding
season would change as of that
date to:
Seasonal pregnancy rate as of
15/20=.75 x 100=75 per cent.
The abortion rate from July 30 to
November 30 would be
figured as follows:
2/17=.117X100=11.7 per cent.
2. Cycles /pregnancy is the
total number of cycles / total number
of pregnant mares. This
calculation is a very important
indication of the
fertility or efficiency of the individual stallion.
Example:
If on April 5, it is determined
that a single stallion was
bred to 25 mares up to that date that have
been called
in foal and of those 25 mares,
20 conceived after only
one cycle, 3 conceived after
having been bred through 2
cycles, and 2 conceived after
having to be bred through
3 cycles, then divide the
number of total
cycles it took
to get these 25 mares in foal [
(20x1) + (3x2 )+ (2x3) = 32
total cycles] by the total
number of mares in foal (25); or
32/25=1.28 cycles per pregnancy.
3.
Pregnancy rate per cycle. (Of the total group of mares to be bred
for the season or to a particular stallion,
what percentage of
mares became pregnant after the first
estrous cycle, after the
second and after the third?)
Example:
At the end of a breeding season
it was determined
that Stallion One bred 30
mares, of which 10 became
pregnant on their first cycle,
and it took two breeding
cycles for 10 more to get
pregnant. Five mares became
pregnant after being bred over
3 cycles , and the final
five mares required 4 cycles
before becoming pregnant.
For Stallion One then:
Pregnancy rate for this group of
mares, after the first cycle
was 10/30=.33x100=33 per
cent. Pregnancy rate for this
group of mares after the
second cycle was
10/30=.33x100=33 per cent.
Pregnancy rate for this group
of mares after the third
cycle was 5/30=.165x100=16.5
per cent. And the
pregnancy rate for this group
of mares after the fourth
cycle was also 16.5 per cent.
Since this group of mares was
bred to only one stallion,
these figures are valid for
evaluating this stallion in
regard to his fertility if we
consider these to be average
mares.
If Stallion Two on the other
hand had been bred to 30
mares during the same season
and it was determined
that after the first cycle, 20
of these mares had become
pregnant and after the second
cycle 9 mares were found
to be pregnant, and the one
mare was bred 4 more
cycles and stayed barren
through the entire season,
then: Pregnancy rate for this group of mares after
the
first cycle was
20/30=.67x100=67 per cent. Pregnancy
rate for this group of mares
after the second cycle was
9/30=.30x100=30 per cent.
So in the case of Stallion Two,
his fertility appears to be
much superior to Stallion One
and therefore could
conceivably handle a much
larger book of mares per
season that Stallion One.
This parameter is very individualistic.
Some stallions are more fertile than others. Pregnancy rate per cycle can be
helpful in determining this, but you cannot determine a stallion’s individual
threshold at which breeding efficiency declines without analyzing the records
closely. This is important information to be able to predict the overall
fertility of a particular stallion and his breeding potential. (How many mares
to book to this stallion for good pregnancy rate?)
Mares bred in one week compared to percentage
of mares bred during that week that were pronounced in foal at 14 to 18 days
after that breeding. When this rate begins to decline, the stallion has begun
to reach his threshold of the number of mares that can be safely bred and
expect good pregnancy rates. Any number of mares over that amount would cause a
lowering of that stallion’s sperm output and his pregnancy rate would go down.
This is covered in detail in Chapter 18, but will require a close analysis of
the graphs.
Determining a stallion’s threshold of
efficiency is very important to a Thoroughbred farm where A. I. is not allowed.
Foaling rate percent of mating that
produce a live foal is determined by dividing the number of live foals by the
number of mares bred the previous season. This can be figured for a particular
stallion or an entire operation; it is usually figured both ways. Foaling rate
provides an overall ratio of efficiency, but it does not determine what most
influenced the overall ratio. More specific ratios, such as pregnancy loss
rate, embryo loss rate, fetal loss rate and stillbirth fetal loss rate, can be
used to identify differences at specific times of gestation.